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ECE 477 Final Report Spring 2010Team 4 Quazyx: Laser Warfare System

Team Members:

#1: Ben Moeller Signature: Date: 6-May-10

#2: Emily Blount Signature: Date: 6-May-10

#3: David Freidin Signature: Date: 6-May-10

#4: Michael Niksa Signature: Date: 6-May-10

CRITERION SCORE MPY PTSTechnical content 0 1 2 3 4 5 6 7 8 9 10 3Design documentation 0 1 2 3 4 5 6 7 8 9 10 3Technical writing style 0 1 2 3 4 5 6 7 8 9 10 2Contributions 0 1 2 3 4 5 6 7 8 9 10 1Editing 0 1 2 3 4 5 6 7 8 9 10 1

ECE 477 Final ReportSpring 2010

Comments: TOTAL

TABLE OF CONTENTS

Abstract 1

1.0 Project Overview and Block Diagram 2

2.0 Team Success Criteria and Fulfillment 4

3.0 Constraint Analysis and Component Selection 5

4.0 Patent Liability Analysis 10

5.0 Reliability and Safety Analysis 14

6.0 Ethical and Environmental Impact Analysis 18

7.0 Packaging Design Considerations 21

8.0 Schematic Design Considerations 24

9.0 PCB Layout Design Considerations 28

10.0 Software Design Considerations 31

11.0 Version 2 Changes 36

12.0 Summary and Conclusions 37

13.0 References 38

Appendix A: Individual Contributions A-1

Appendix B: Packaging B-1

Appendix C: Schematic C-1

Appendix D: PCB Layout Top and Bottom Copper D-1

Appendix E: Parts List Spreadsheet E-1

Appendix F: FMECA Worksheet F-1

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Abstract

The Quazyx: Laser Warfare System project is a new take on laser tag systems that incorporates power-up elements of video games in a laser tag system that is less expensive than commercial systems. It was designed in the spring of 2010 as part of the Purdue University Digital Systems Senior Design class for the college of Electrical and Computer Engineering. The project was selected to incorporate the wireless communications interest of several team members with the desire to produce a genuinely fun product. The following report contains a revised form of all the design specification and analysis documents produced throughout the semester along with figures, schematics, PCB layouts, and referential sources that were utilized in the creation of the final product.

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1.0 Project Overview and Block Diagram

The Quazyx system consists of two vests with four sensor modules each connected via phone wire and standard Ethernet to their respective gun components. Each gun component contains a PCB with microcontroller module, LCD display, LEDs, and trigger. Over the RF module on the PCB, the gun/vest combination communicates with the respective RF module on the base station PCB mounted within a project box. Also within the project box on the base station PCB is the decoder module for the keypad input to control the game and the LCD panel to display output.

The primary game control logic and commands come from the base station PCB and associated keypad and LCD display. The gun/vest serves mostly as an elaborate wirelessly connected sensor array that provides very limited control over the game to the use beyond firing or physically moving the sensor pods out of range of another gun. Only a small local display of the individual player’s status is shown.

The final, assembled playable laser tag system is shown below in a photograph labeled as Figure 1.1. The general internal structure and interconnection of the PCB and off-board components is visible in the block diagrams shown in Figure 1.2

Figure 1.1 – Final Deliverable Laser Tag System

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Figure 1.2 – Final Block Diagram

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2.0 Team Success Criteria and Fulfillment

1. An ability to wirelessly transmit a shot and receive a hit via Infrared

Reliable communication of Infrared shots was successfully established through both IR LED modules (for rifle and shotgun modes) and received by the vest pack sensor arrays. Player IDs that are associated through the RF handshake protocol are successfully propagated to the IR communication to distinguish between players.

2. An ability to remotely enable and disable the gun/vest pair

Enabling and disabling the gun vest pair happens, as envisioned, both as a result of RF communication and as a reaction to Infrared. An individual in an administrative position can utilize the base station to start and end the game, transmitting the appropriate packets over the RF channel, and remotely enabling or disabling the gun and vest. Additionally, through the course of shots and hits in a laser tag game, the vest is disabled on proper Infrared reception and re-enabled after several seconds to represent a “kill.”

3. An ability to control game operation using base station keypad

The base station keypad can be used to navigate all game setup and operation menus on the base station module and causes the proper RF routines to be activated in order to effectively control the game operation.

4. An ability to wirelessly communicate game statistics to base station via RF

Trigger pulls as well as kills and deaths are transmitted to the base station as they occur on the various roaming gun/vest modules. The base station receives this information properly and displays it on the LCD panel both as it occurs for the game administrator as well as in an aggregate form after the game has been ended.

5. An ability to provide user with local display of game information

The LCD panels on the gun/vest modules update as the gun transitions between startup, registration, game play, and game over modes. Also, messages are displayed at the moment of a kill from another player to identify that player. Lastly, packets received from the base station every thirty seconds are displayed to show the remaining game time and collected kill and death information.

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3.0 Constraint Analysis and Component Selection

3.1 Introduction

The Quazyx Laser Warfare System is designed to emulate professional laser tag systems used within recreational facilities and military exercises while being low cost, completely portable, and constructed from readily available parts. As the major portion of the system is the portable gun/vest pack, power and size will be the primary constraints in selecting components and packaging the final product. Additionally, to ensure successful completion of the project within the next several months and on a limited budget, we have prioritized manufacturers whose parts have been introduced to our team in previous design projects.

3.2 Design Constraint Analysis

The major constraint of the laser tag system is the portable nature of the gun/vest packs that are deployed to each participant in the game. As such, each pack must consume minimal power such that the batteries used can be selected to be as light as possible to prevent user fatigue. To keep costs low, standard C or D cell batteries are intended to be used to power the device. Additionally, the mature technologies of infrared and ISM-band radio frequency will be considered as a part of the portable, wireless nature of the game packs to ensure a reliable real-time solution to communication. Lastly, in a high-adrenaline game such as laser tag, the final design consideration will be durable packaging that can withstand running, jumping, dodging, and crawling expected to be a part of a successful and entertaining laser tag experience.

3.3 Computation Requirements

Computation within the portable gun-vest portion of the system is limited as this microcontroller serves mostly to relay information occurring within the game to the base station module. However, as players would like data to update in real-time, the microcontroller must be sufficiently powerful to capture shot and hit data, process it, relay it to the base station, and display the response to the user as quickly as possible.

The base station module requires more computational power as it must manage a one-to-many relationship with the various gun pack devices in the system potentially switching between identification codes to speak with all compatible devices within an area in limited time. Integer mathematics will suffice as the primary numerical computation consists of incrementing and decrementing various score values and tracking the current game time. Additional features like game statistics, radio communication, and display are not computation intensive and are likely to be entirely dependent on the speed of serial I/O from the microcontroller to the various

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peripherals. Most microcontrollers available to us are clocked within the megahertz range, allowing plenty of speed for this communication.

3.4 Interface Requirements

For radio frequency communication, the microcontroller device needs to interface with the RF transceiver via three control pins: a bi-directional serial pin, a transmit-ready pin, and a receive-ready pin. Since the RF transceiver selected from Linx Technologies supports standard serial communication, we expect to interface with a standard SCI component of the selected microcontroller or general purpose I/O pins. Up to eight additional general-purpose I/O pins will be used to communicate data from the microcontroller to the transcoder module responsible for RF communication.

A serial shift register will be required in each of the gun packs as well as in the base station to send data into a Hitachi-compatible LCD display screen. The 8-bit shift register will service the data lines on the LCD panel using only one output of the microcontroller, and an additional two pins will be needed to select command vs. data and to clock the commands into the peripheral device.

In the base station module, to control the operation of the game and command the microcontroller to display various statistics on the base station’s LCD panel, a keypad scanner will be utilized to minimize I/O pins consumed on the microcontroller as well as to offload the scanning work.

Current sourcing requirements from the microcontroller are minimal as it primarily drives other ICs to perform communication functionality. The only concern may be the LEDs in the gun/vest unit as they will likely require high current for bright, long-distance IR transmission. This concern is easily mitigated with inexpensive switching transistors, and therefore the chosen microcontroller seems sufficient for the application.

3.5 On-Chip Peripheral Requirements

On board, an ATD interface is needed to monitor the status of the RF module as well as to generate random numbers efficiently. An SPI interface will be necessary for LCD communication via the shift register. Change notification modules would be useful to detect trigger pulls and button presses on the keypad without the need for polling. Additionally, input capture modules to capture the time when an IR beam is detected will be useful for receiving IR reliably. Additionally, three timers are necessary for the delay routines inherent to IR and RF communication as well as to set up the sampling of the ATD. For details of the peripherals that exist in our selected Microchip microcontroller, see [1].

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3.6 Off-Chip Peripheral Requirements

The off-chip peripherals we will use include a keypad encoder in the base module to offload scanning and interrupt functionality, a shift register for port expansion use with the LCD panel in both the base and the game packs, and the Linx RF transcoder that will offload the handling of collision detection, packet encoding and decoding, and all other major wireless carrier activities for the radio frequency transceiver.

3.7 Power Constraints

The portable gun-vest portion of the system will need to be battery powered. Our initial estimates look into using standard off-the-shelf C or D cell batteries depending on the desired life time of each charge and how much current we expect to draw. In either case, three batteries in series will provide 4.5v which is well within the operating range for all components selected in our system. Rough estimates of total power stored within D cell batteries are approximately 12,000 to 18,000 mAh per battery [2] which we believe will yield at least eighteen hours of play time based on calculations of current usage of all the system components.

For the base station unit, we use the same configuration of three standard battery cells to make the design uniform with the portable packs. A point of note is that the base station will not need to light up all the LEDs associated with the portable packs, so it will require less current and last for a longer period of time on the same battery cells as the portable packs. A battery powered base allows the game to be taken and set up outdoors in any location, a potentially desirable feature.

3.8 Packaging Constraints

For the portable vest and gun combination portion of the Laser Tag system, the overall package must be as light in weight as possible to minimize fatigue of the players running with the device. Items with significant weight like batteries were placed near the handle of the gun to minimize torque on the player’s hand as it grips the gun handle. The vest will be made of durable nylon or some similarly tough material, and the gun was selected from various ABS plastic designs available from major toy manufacturers. The cable that runs between the gun and vest combination was selected as a piece of durable Ethernet cable that allows range of movement while protecting the power and communications cables inside.

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3.9 Cost Constraints

In comparison with our design, competing consumer level laser tag products on the market range in price from $25 to $600 depending on features, range, quality, and inclusion of an additional wearable vest or heads-up display [3]. Commercial systems from companies like Laserforce and Laser Runner start at $30,000 for an entry level system and additional packs around $2,000 each [4]. As a competitor to these products, we would like our system to be on the order of the consumer-level systems in the several hundred dollar range while including central administration, statistics, and additional custom features normally not seen outside the commercial arena.

3.10 Component Selection Rationale

General rationale for minor component selection is manufacturers and interfaces that are familiar to members of our team from previous school-related or personal design projects. Additionally, we attempted to select components that were as inexpensive as possible since we had to fund our own development. An example is the Hitachi-compatible parallel data LCD panels included for user interfacing on the gun packs versus serial-only interfaces.

For the microcontroller, one of the two major components, we chose from several options within Microchip’s PIC 16-bit controller line. Several team members are familiar with PIC products and expect shorter development time with these products. Additionally, all the PIC controllers considered ranged in price from $3 to $6. Specifically, two candidates for the microcontroller included the dsPIC33FJ32GP304 and the dsPIC30F4011. The dsPIC33FJ32GP304 boasted a higher precision 12-bit A/D converter, a larger 4 kb of RAM, and an additional SPI interface [5] while the dsPIC30F4011 has a larger 48kb of Flash program memory, an equal 2 UART interfaces, six PWM channels, a larger 2.5v to 5.5v input operating voltage range, and is one dollar more expensive at $4 per unit [1]. Ultimately we selected the dsPIC30F4011 with larger voltage range such that it could be operated on two or three standard batteries (3 or 4.5v) and because while generally comparable, free samples were available of this model.

In terms of radio frequency modules, the other major component, we chose from three main manufacturers: Linx Technologies, Texas Instruments, and Freescale Semiconductor. In the inexpensive ISM-band transceiver lines, the Texas Instruments CC110RTKR [6] and Freescale MC33696 [7] were similar products requiring an external crystal oscillator, having an SPI interface to a microcontroller, operating on a wide variety of ISM bands, and priced at around $6 per module. The Linx Technologies system, in contrast, is more expensive at $22 for antenna, transceiver, and codec; targets only one specific ISM frequency of 418 MHz; and has a low data rate of 10,000bps at up to 3,000ft [8]. However, the Linx system is more attractive in that it is nearly a turnkey RF solution where collision detection, interference, and many-to-one

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communication is handled by the separate codec module eliminating the need to write extensive software code to handle such functionality. As such, we selected the Linx Technologies system for our design despite being slightly contrary in the price category for the additional functionality while remaining at approximately the same power consumption (about 14mA transmitting) as comparable models.

3.11 Summary

Ultimately the design for the laser tag system consists of readily available, inexpensive, and proven radio frequency, keypad, and LCD interfaces connected to a familiar and well-equipped microcontroller. While cost and size remained a concern in part selection, in select cases like the RF module, ease of use and interfacing was prioritized. However, as a whole, the system will be low enough on current draw to be run for many hours on one set of standard cell batteries and will fit securely into hard plastic based packaging to be light, portable, and rugged enough to create an enjoyable system.

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4.0 Patent Liability Analysis

4.1 Results of Patent and Product Search

4.1.1 Electronic Tag Game (6,530,841 Filed: 06/26/2001)

A wireless device-enabled tag game is presented in this patent. Below is a brief description of the patented design.

“The game allows players to find and tag each other with their wireless devices. When one player's device is in close proximity to the device of another player, the tag is enabled by the wireless devices, thereby eliminating the need for physical contact to make the tag. The wireless device of either player can display the status and results of the game. Because the game can be defined in a particular space and can include anyone with an appropriate wireless device, the game may remain ongoing such that players may join and part at will without greatly affecting the game.” [9]

The system in patent 6,530,841 claims to be “an electronic system for playing a game of tag” which incorporates “a radio-frequency configuration.” [9]

4.1.2 Interactive Light-Operated Toy Shooting Game (5,741,185 Filed: 02/05/1997)

The system described in this patent operates in a somewhat similar way to the Quazyx system. Below is a description taken from the patent.

“The invention provides a toy light projector or light gun and player-worn and self-propelled toy targets which detect light emitted by a toy light gun, and a toy shooting game which includes at least one toy light gun, and at least one toy target.” [10]

A few claims made in this patent are possible infringed by the Quazyx system. The first of these is “a toy light projector used in a toy shooting game.” [10] The second claim which may be infringed is “an electrical circuit... which controls energization of said light source according to a selectable code and thereby causes said light source to emit light with the selected code.”[10]

4.1.3 Electronic Game with Infrared Emitter and Sensor (5,904,621 Filed: 01/16/1998)

This patent is extremely similar to the Quazyx system. A brief description is below.

“A hand-held electronic toy gun and target apparatus facilitating a game of tag using infrared light communications between a plurality of players. An electronic controller is coupled to a transmitter for sending a series of encoded infrared light signals and a receiver for detecting

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infrared light signals.” [11]

There are multiple claims made in this patent which might be infringed by the Quazyx system. The first, and most notable, of these is “an apparatus for facilitating a game of tag using infrared light communications between a plurality of players.” [11] The patent also claims to have “at least one switch coupled to [an electronic] controller for generating a plurality of game functions” and “a transmitter coupled to said controller for sending a series of encoded infrared light signals responsive to said at least one switch.” [11]

4.2 Analysis of Patent Liability

4.2.1 Patent Liability Analysis for Electronic Tag Game

The electronic tag game which is described in patent 6530841 is, in many ways, similar to the Quazyx system. It claims an RF wireless system to communicate user data to other individuals playing the game. It also claims to be an “electronic system for playing a game of tag.” Both of these claims are very similar to claims made by the Quazyx system. However, by nature of their use in both systems, they are substantially different.

In the Quazyx system, RF communication is only used to transmit game statistics and “who hit who” data. This information is broadcasted from a gun-vest pair and received by a base station. It is then re-broadcasted by the base station and received by the appropriate gun-vest pair to which the data applies. At the end, the base station displays all of the data which has been compiled during the course of the game. In the Electronic Tag Game system, RF communication is used to convey player location data to each player in the game and only players. This data is displayed on a screen and the players use it to track down other players in the game. There is no base station in this implementation and the information which is being transmitted is entirely different than game statistics.

Additionally, the method of communicating a “tag” in the Electronic Tag Game is substantially different from the method used in the Quazyx system. In order to communicate a “tag” in the Electronic Tag Game system, players must be within some set proximity of one another. The system detects this proximity and automatically transfers the “tag” from one player to the other. In the Quazyx system, an encoded IR light beam is sent from one gun-vest pair and detected by another to communicate a “tag.” This is arguably a substantially different method of communicating a “tag.”

4.2.2 Patent Liability Analysis for Interactive Light-Operated Toy Shooting Game

The Interactive Light-Operated Toy Shooting Game is also very similar in a few ways to the Quazyx system. The most notable of these is that it uses an encoded IR light beam to communicate between a gun and a target. This encoded light beam is used to distinguish between

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two types of firing codes on the gun. The first code is used only to communicate a shot and let the target accumulate hit data. The second code is used to reset the hit data on the target.

Like the Interactive Light-Operated Toy Shooting Game, Quazyx also uses an encoded IR light beam to communicate data between gun and target. Unlike the other system however, Quazyx uses a specifically encoded signal to communicate player information such as the vest number. This information is radically different than sending a reset signal via IR. Additionally, the method of communicating this data is substantially different. Both signals are encoded, but while the Interactive Light-Operated Toy Shooting Game uses a binary signal to differentiate between signals, Quazyx uses a different duty cycle for each gun-vest pair instead of communicating the information as a binary signal.

4.2.3 Patent Liability Analysis for Electronic Game with Infrared Emitter and Sensor

The system described in this patent is extremely similar to the basic functionality of the Quazyx system, especially when referring to the IR communication. This system uses an encoded IR signal, sent from a gun to a vest, to communicate player specific data in order to distinguish between users. In essence, this is exactly the same as the IR communication system being developed for Quazyx.

Quazyx uses an encoded IR signal specifically for communicating user identification data. Since this is the exact implementation used in the Electronic game with Infrared Emitter and Sensor, Quazyx infringes on this patent.

4.3 Action Recommended

4.3.1 Action Recommended for Electronic Tag Game

It was determined in the discussion in section 4.2.1 that Quazyx does not infringe upon this patent. Because Quazyx does not infringe, it is not necessary to take any further action regarding this patent.

4.3.2 Action Recommended for Interactive Light-Operated Toy Shooting Game

It was determined in the discussion in section 4.2.2 that Quazyx does not infringe upon this patent. Because Quazyx does not infringe, it is not necessary to take any further action regarding this patent.

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4.3.3 Action Recommended for Electronic Game with Infrared Emitter and Sensor

It was determined in the discussion in section 4.2.3 that Quazyx does in fact infringe upon this patent. Because Quazyx infringes, it will be necessary to request licensing from the patent holders and pay them royalty fees.

4.4 Summary

This section includes an analysis of the patent liability for the Quazyx laser tag system being developed. It was included in the above sections that the current Quazyx design does infringe upon US patent 5,904,621, Electronic Game with Infrared Emitter and Sensor. Since Quazyx infringes, it will be necessary to request licensing from the patent owners and pay them royalty fees.

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5.0 Reliability and Safety Analysis 5.1 Introduction

Our project is a laser tag system intended for playing in an indoor or outdoor environment. The game of laser tag carries with it some inherent safety risks, due to high-adrenaline physical activity in a simulated warfare environment. The opportunities for injury due to player actions and environmental hazards are completely out of our control; the most protection we can offer is a set of warnings and appropriate game rules in the user manual. However, the physical nature of the game must still be taken into account in designing our system to be robust enough to withstand a certain minimal amount of jostling. Any parts which are not securely fastened to and completely enclosed within the packaging are at risk of being damaged in ways which cannot be entirely predicted.

In addition to the physical hazards of the game, our system also carries a potential safety hazard in the form of a laser, used for visual targeting feedback. The website laserpointersafety.com [15] explains the damage that can be caused by shining a laser into a human eye. However, it also points out that for lasers rated at 5 mW or less (ours is 3 mW), a normally functioning “blink reflex” is sufficient to prevent accidental damage. It is still possible to cause retinal damage by purposely shining the laser into an eye and keeping that eye open, but if we simply limit the duration of a shot to 1 second or so, it would be effectively impossible to do so without deliberately misusing the product.

The final safety concern is the power supply. Our units are powered by three standard D-cell batteries. These were chosen for various reasons, including cost-effectiveness and reliability. Alkaline batteries have been around for over fifty years, and are much more stable and reliable than newer high-capacity batteries such as lithium-ion. The primary issues that can result from various power problems are sparking and leaking. Sparking could occur with any short-circuit anywhere in the device. In order to prevent harm to the user from sparking, all electrical components are fully enclosed and insulated from the user. Our batteries will only reach a combined total of 4.5V, with only 3V going to the PCBs, so as long as the insulation is good, there should be no risk to the user from sparking. The other possibility is that the batteries could leak potassium hydroxide (KOH). There should not be any immediate danger to the user, as the batteries are fully enclosed in either the gun or base station. The possibility of danger arises when the user attempts to remove the failed batteries. Unfortunately, there is not much we can do to lessen this risk aside from placing appropriate warnings in the user manual.

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5.2 Reliability Analysis

The three components I will focus on for analysis will be the microcontroller, the RF transceiver, and the LEDs. The microcontroller (dsPIC30F4011) is probably the most complex component in our design. It has the most pins of any device, and is the most general purpose of the devices we are using. The RF transceiver is also a fairly complicated component, and it has the highest operational frequency in our project, as it must transmit an RF signal at 418 MHz. Finally, the LEDs make up the majority of the current drawn by our system, and there are more of them than any other component.

Table 5.2.1 - Microcontroller (Microelectronic Circuit Model)Parameter name Description Value CommentsC1 Die complexity 0.14πT Temperature coeff. 1.5 Assuming room temperatureC2 Pin constant 0.015 Value for 40 pinsπE Environmental constant 6 “Ground Fixed” environmentπL Learning factor 1 In production for more than 2

yearsπQ Quality factor 10 Non-military gradeλP Predicted failure rate 3 Per 106 hoursMTTF Mean time to failure 333333 Years

Table 5.2.2 - RF Transceiver (Microelectronic Circuit Model)Parameter name Description Value CommentsC1 Die complexity 0.14 Assuming similar complexity

to our microcontrollerπT Temperature coeff. 1.5 Assuming room temperatureC2 Pin constant 0.0041 12 pinsπE Environmental constant 6 “Ground Fixed” environmentπL Learning factor 1 In production for more than 2

yearsπQ Quality factor 10 Non-military gradeλP Predicted failure rate 2.346 Per 106 hoursMTTF Mean time to failure 426257 Years

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Table 5.2.3 - LEDs (Diode Model)Parameter name Description Value CommentsλB Base failure probability 0.0012 General purpose diodeπT Temperature coeff. 3.9 Assuming room temperatureπS Stress coefficient 0.054 Not a tranzorbπC Contact construction

factor1

πQ Quality factor 8 Plastic-encapsulatedπE Environmental constant 6 “Ground Fixed” environmentλP Predicted failure rate 0.0123 Per 106 hoursMTTF Mean time to failure 81300813 Years

While the predicted failure rates for the microcontroller and RF transceiver are rather high, the values used in the calculations are worst case scenarios. In particular, the quality factor is probably somewhat below 10, and the temperature coefficient for the microcontroller is probably much lower than this upper bound due to the fact that it is being used at the lower end of its voltage range [13]. We could further reduce the heating of the microcontroller by reducing its clock rate, but there is a point of diminishing returns. If heat was found to be a serious issue, we have enough room that we could easily apply small heat sinks to certain components.

5.3 Failure Mode, Effects, and Criticality Analysis (FMECA)

Appendix F contains circuit schematics for various subsystems of our product. Each system has its own potential failures associated with it, and the failures for each system affect the game in different ways. For the FMECA tables in Appendix F, three levels of criticality are used: Low, Medium, and High. High criticality indicates a possibility of harm to a user. Low and Medium criticality are differentiated by both importance to gameplay and ability to replace with a spare component. If a particular failure still allows the game to be played or the broken part is easily replaceable by the user, the failure has low criticality. Otherwise it has medium criticality. Note that the parts that are not replaceable are generally critical for gameplay, so the question of whether a non-replaceable failure that doesn’t break gameplay should be medium or low criticality can be ignored. The criticality of each failure is briefly explained in its row in the FMECA tables. For high criticality failures, the probability of failure should be less than 10-9. For medium criticality failures, a rate of around 10-6 is reasonable, and for low criticality failures the rate can be higher.

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5.4 Summary

Our project has various safety hazards associated with it. However, many of these hazards are part of the normal intended usage scenario of the system. Because none of the components we are using are bleeding edge technology, they are expected to be very reliable, especially if we avoid using them near the limits of their specifications. Very few of our potential failures have a possibility of harm to the user, and we are doing all we can at our end to prevent such harm.

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6.0 Ethical and Environmental Impact Analysis

6.1 Introduction

The Quazyx Laser Warfare System is a modified laser tag game implemented using IR shots and RF communication between the gun and vest units and the base station. Although the software of the system recognizes the IR signal as a shot, an actual laser has been included as a visual cue to the player. Lasers can be potentially harmful in many ways, and this is a major ethical concern. Also due to the inherent violence in any simulated warfare system, it would be unethical to expose impressionable youth to this violence, much in the way that violent movies are age restricted without parental consent.

A unit of this system is composed of a fabric vest, plastic gun, various electronic components, D-cell batteries, and a plastic box for the base station. All components are designed to be durable to withstand damage during high activity play; therefore, the expected lifetime of this product is fairly lengthy. The only components that will have a shorter lifespan than the rest of the product are the batteries, which have been specifically chosen to be easily replaceable and recyclable.

6.2 Ethical Impact Analysis

During the manufacture and production of this product, precautions should be taken to resolve several ethical problems related to and because of this product. Since this product will be used in high intensity rough play, the product should be thoroughly tested to withstand brutal environments and handling. In the event that the product is dropped, smashed, bumped, or crushed, it should be able to endure with reasonable function. Testing should simulate these actions. A vibration chamber would be ideal to be able to test the ability of the circuits within the product to withstand extreme actions. The components of this product should not jar loose or break including circuit components and the PCB housed within the gun. To secure all parts, the PCB will be screwed, or otherwise securely fastened, to the gun housing. The components on the board will be securely soldered or fastened with a secure header. To prevent the cables from becoming stressed by pulling from the gun, a strap will connect the gun to the vest so that in the event the gun is dropped, the weight is handled by the strap and not the cables. The plastic housing of the gun itself has been designed to withstand damage due to the fact that the housing originated as a squirt gun, a product that must withstand similar play style factors. By designing the product to withstand high intensity play and damage the user will benefit from the long lifecycle of this product.

The other major ethical concern of this product is the use of the laser. Firstly, in the event that the laser is directed at the eye, it can cause damage. According to the FDA, which regulates all

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laser usage, laser products should have labels stating that the product complies with the federal laser standard [16]. Any laser that uses more power than 5mW is directly regulated by the FDA, whereas those powered by less than 5mW can be manufactured and used recreationally. This laser warfare system uses a 3mW red laser, which is safer for users because of the low power and the color of the laser since the eye is less sensitive to the color red. Flash blindness occurs when the eye is exposed to intense light and can last anywhere from a few seconds to several minutes [17]. This is a potential hazard of the game, and as such, the hazard has been minimized as much as possible by the choice of a low power red laser and the inclusion of a warning label on the packaging cautioning the user to avoid staring into the laser beam. Secondly, the misuse of the laser is another ethical concern. This laser tag system has been designed for outdoor use, and, as such, playing in an open area could cause severe damage. For example, playing near roads could cause flash blindness for the drivers which could cause car crashes, or also a bystander or bicyclist could be startled by the laser and trip and fall. To remediate this potential for harm, a caution in the user documentation would suggest playing in an area away from roads and bystanders and to avoid shining the laser at any overhead airplanes or distant mountains.

Lastly, due to the violence inherent in a warfare simulation system and the potential for mischievous misuse, a caution would be included in the user manual to suggest restriction of use of this product to users over the age of 18. Since ideally this product would be sold in stores, a way to prohibit use would be difficult; therefore, only a cautionary statement in the user manual is feasible.

6.3 Environmental Impact Analysis

The environmental impact of this product is minimized due to the design. It has been designed to last for a lengthy period of time and to withstand hazardous environments. The only parts that will need regular replacement are the non-rechargeable D-cell batteries. The product has been designed to run from alkaline D-cell batteries because of the minimal environmental impact. Many places alkaline batteries are do not require special disposal; however, in the user manual, it would be suggested to recycle the used batteries. Many cell phone companies offer this service for free [18].

In the event that the product should break, guidelines for disposing the parts correctly will be included in the user manual. The current product uses a mass produced squirt gun as the basis for the laser gun. The plastic in this gun is non-recyclable; however, it can be safely disposed in the city dump. Likewise, the plastic coverings for the base station and vest sensor pods can also be safely disposed to the local trash repository. The fabric material is made of durable polyester; however, it will also decompose without any environmental impact other than the cubic space it will occupy in the dump. The last concern for disposing this product correctly is disposing the electronic components correctly. Without belaboring the point, the PCB contains lead, and the

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other various electronic components also contain heavy metals that are considered harmful to the environment. One suggestion of disposal of the electronic components would be to donate the materials to a local high school to use in their computer courses as examples. It would also be suggested in the user manual, to dispose of the materials at a local electronics recycler.

6.4 Summary

In brief, the major ethical concerns for the Quazyx: Laser Warfare System include reliable durable design, laser hazards, laser misuse, and violence exposure to minors. These concerns are addressed by extensive durability testing, a laser hazard label included on the packaging, a caution in the user manual stating play should be away from bystanders and roads, another caution directing users to refrain from pointing lasers at far away objects, and lastly a parental advisory stating that play should be restricted to ages 18 and up.

The major environmental concerns include battery disposal, vest and plastics, and proper disposal of electronic components. These environmental concerns have been addressed by utilizing a battery that is considered less hazardous to the environment, the use of bio-degradable plastics and fabrics, and instructions in the user manual to dispose of electronic components at a local recycler or high school.

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7.0 Packaging Design Considerations

7.1 Introduction

Our project idea is a conventional Laser Tag game system with additional Halo-inspired features including multiple firing modes and defensive features. It is an infrared and RF-based system that will incorporate several gun and vest pairs to simulate a virtual war game. The gun housing will be the shell of a water gun while the interior will include most of the electronics for the system. The vests will be comprised of a heavy-duty fabric and will have four sensors attached.

7.2 Commercial Product Packaging

7.2.1 Product #1 – LT-11.5 Laser Tag System This professional laser tag system is known as the LT-11.5 and is the system of choice for newly started laser tag arenas [19]. From a packaging standpoint, this laser tag system is very well built and durable. It is meant to stand up to many years of constant use.

The gun is comprised of a hard plastic shell with a

sensor and LED built in. Additionally, this system requires two hands to be used on the gun when firing. The red button at the end of the gun needs to be pressed down when firing. This is a feature we will not be including in our design. We are also not planning to have a sensor built into the gun. Also, the commercial gun is designed to be extremely durable and made out of hard plastic. Our gun packages are made from modified squirt gun housings, so they will be less durable. Aside from these minor differences, our system’s gun will be very similar to the gun in the LT-11.5 system.

The LT-11.5 vest is also very similar to the vest we will be using in our design. It is durable and includes four sensors to detect a shot at the vest. Since this is a professional system, it is obviously a very well-designed system. However, our vest will not be as bulky as this design. The LT-11.5 vest is comprised of hard plastic and covered with a foam layer. Our design will be made of a heavy duty fabric and will conform to the user’s body. Also, the LT-11.5 has most of the electronics housed in a hard plastic case on the front of the vest. Our design idea is to have

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the PCB and batteries inside the gun housing. This will allow us to connect our off-board electronic components with minimal cabling and keep things more compact. Our vest will have only the four IR sensors built into it and will have minimal wiring routing signals from these sensors back to the gun.

7.2.2 Product #2 – Humvee Combat Tactical Vest

The Humvee Combat Tactical Vest (HCTV) is very durable and lightweight [20]. By nature, this vest can be worn by different many different sized people, where the LT-11.5 vest was hard plastic and would only comfortably fit athletic middle-aged people. In our vest design, we will be using a fabric similar to that used in the HCTV. Our vest is intended to be lightweight but durable and comfortable. The HCTV design accomplishes these requirements very well.

One main difference between our design and that of the HCTV is that we won’t be using a

zipper-up vest with arm holes. Our vest is designed with open sides and will have buckles on both sides to allow adjusting for larger or smaller wearers.

7.2.3 Product #3 – Radio Shack Project Box [21]

Our base station will be a very simple design. It will be a large PCB housed in a Radio Shack project box with access to an external keypad and LCD screen. Due to the simplicity of this design and the unique nature of our base station, it was impossible to locate any commercial product which was similar enough to reference.

7.3 Project Packaging Specifications

The gun housing for our laser tag system will be the shell of a Wal-Mart-brand water gun. This housing provides us with an excess of space in the reservoir tank to place electronics and wiring. It is also lightweight, durable, and ergonomically friendly. A CAD representation of the gun housing is provided in Appendix B of the final report. It is a very accurate representation of the size of the gun but has no detail on the surface of the shell as this is unnecessary.

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The vest for our system is going to be hand-made by Emily from a sturdy nylon fabric or equivalent. It will have a buckling system to allow the wearer to tighten it to their chest size. The CAD drawing provided in Appendix B of this document is a fair representation of the size and shape we will be using. Also included in this drawing are the placement locations of the sensor pods. Two will be located on the shoulders; the other two will be located on the front and back.

Our base station is simply going to be a box, roughly 6” x 8” x 3” in size. This box size was chosen to leave enough room to accommodate for all of our electronic components such as the LCD screen and keypad. Additionally, the inside of the box allows enough room for the PCB and batteries. A CAD representation of the final base station design is provided in Appendix B of the final report.

7.4 PCB Footprint Layout

Thankfully for our project, we are not really constrained at all by PCB size. The only thing we needed to make sure was that there was enough space available for metal fill to provide the RF chip with an antenna. This metal fill was the main constraint of the overall PCB size for our design.

The base station PCB is nearly identical to the gun PCB. The main difference is that the base station PCB has connections for the keypad and keypad encoder. However, this only requires the placement of one IC and a header, so this causes minimal size constraints. Both the LCD and keypad will not be connected directly to the PCB but will be connected via a cable and mounted to the external face of the project box.

7.5 Summary

This report includes multiple comparisons of product similar to our own which are already in existence as well as specifications that will be used in the packaging of our product. It also includes detailed CAD drawings of our product.

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8.0 Schematic Design Considerations

8.1 Introduction

The laser tag system is composed of a base station, and two vest and gun combinations. The base station will include a keypad to enable users to input different game modes, an LCD screen to display game statistics, an RF transceiver to communicate with the vests, a header to enable programming of the microcontroller, and lastly a power supply. Each vest will have several sensor pods, placed on the shoulders, front and back that will contain IR phototransistors to detect ‘hits’ and color LEDs to display current status of the player (alive or dead and color will indicate team). The vest will be linked through an Ethernet cable to the gun with IR detector signals (a total of four, one for each pod), LED transistor signals (to control LED blinking), power, and ground.

8.2 Theory of Operation

Each subsection of the circuit is directly controlled by the microcontroller [22], whether on the base station or on the gun and vest, except for the trigger which is controlled by the user and is a simple switch that is pulled down when closed and otherwise pulled high through a pull-up resistor. One major subsection of the circuit is the RF transceiver. The transceiver has a transmit-or-receive enable pin that is directly controlled by the microcontroller. When the T/R pin is enabled to transmit, then the data pin is in input mode, and when the T/R pin is enabled to receive, then the data pin is in output mode [23]. The microprocessor handles the encoding and decoding of the signal passed through the data pin. Therefore, when the microprocessor sends the T/R pin to transmit, the data line becomes an input and receives data from the microprocessor. The transceiver then transmits the data by use of Carrier-Present Carrier-Absent modulation. This means that logic ‘1’ is represented by the presence of a carrier, and logic ‘0’ by the absence of a carrier. The signal is passed to an antenna and broadcast. The data is then received by the other antenna and filtered and amplified to recover the original signal, and output on the data pin which is an output to the microcontroller. Therefore the second microcontroller receives the data from the first microcontroller and this is how hits will be registered by the base station and the signal to deactivate hit vests will be transmitted.

When hits are registered they will be displayed on the Newhaven Display LCD screens [24] of both the base station and the gun. Therefore, the LCD screen is another major subsection of the circuit. An 8-bit shift register from Fairchild Semiconductor [25] is used to interface with the microcontroller through the SPI ports, mainly clock and data out. The data is shifted out of the microcontroller and clocked into the shift register. Then when the LCD screen is enabled through the enable pin, the data is shifted into the LCD panel where it is displayed.

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Another indication of a ‘hit’ is through the status of the LEDs on the vest. The LEDs are controlled through the general I/O pins of the vest microcontroller. Therefore, when the gun microcontroller receives the command through the RF to deactivate the LEDs to simulate the hit, the microcontroller drives the LED pins low. There are a total of two LED pins and each pin is connected to the base of four 2N2222 BJT transistors. Although BJT transistors don’t switch as fast as MOSFETs, the LEDs don’t need to blink that fast to require MOSFETS, so it was decided to use the 2N2222 because they are cheap and will fulfill all requirements. The collector of each transistor connects to the two LEDs which then each connect to a resistor and power. The emitter is connected to ground. When the pins are driven low, the transistor turns off and cuts power to the LEDs thereby also turning those off. The vest then simulates a hit because the vest is ‘dead’ when the LEDs are dark. The LEDs will be connected to 4.5V and the current though each LED will be 20mA, which was determined to be plenty bright enough. For the blue LEDs the required resistance was 31.5ohms because the forward voltage drop is 3.17V. For the red LEDs, because they have a forward voltage drop of 1.8V, the required resistance to keep the current through the red LED at 20mA is 100ohms. We decided to not include an LED driver because construction on the sensor pods had already begun, and we felt that this design was simple enough to negate the need for an LED driver.

The last major circuit subsection are the IR diodes used to send the shots and the IR phototransistors used to detect each shot. There will be two IR diodes. One will be short range and wide angled so simulate a ‘shotgun’ blast. The other IR diode will be inside a barrel with a lens at the end that will focus the IR light into a focused beam, simulating the ‘rifle’ shot. Each diode will be controlled by the PWM of the microcontroller. The PWM pin will connect to the base of a transistor which will turn on or off according to the voltage level of the pin and thereby also turn on and off the IR diode, exactly like the circuitry for the status LEDs. The 2N2222 transistor will still be used to control the switching of the IR LED. For encoding of the IR signal, please refer to the software design section. Several phototransistors will used to detect shots to increase the likelihood of a shot being detected. Each sensor pod will have three phototransistors facing different directions with the signal detection pins tied together. Therefore each sensor pod, four total, will have a detection signal that will connect to the input capture pin on the micro. When the phototransistors receive the IR signal the transistors turn on and the pin of the microcontroller will be pulled low. In the off state the pin is pulled high through a pull-up resistor. Therefore the microcontroller will detect the hit. Modulation of the signal to communicate the ID of the shooter is also covered in the software design narrative, no analog circuitry is needed.

8.3 Hardware Design Narrative

Firstly, the SPI subsystem of the microcontroller will be used to control the LCD screens of both the base and guns. The clock and data out pins will interface with the shift register to display the

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data on the microcontroller. There is only one SPI clock pin, pin 43, and pin 44 is the only SPI data out. Secondly, the PWM subsystem will be used to control the pulsing of the IR LED so that each gun vest pair may be identified by the unique frequency of the IR LED. The PWM will control the frequency and duty cycle of the LED. The choice of PWM pin is flexible since all PWM pins can also be used for general I/O. One analog to digital pin will be used for the RF transceiver to detect the strength of any RF signals in the immediate area. The RSSI (Received Signal Strength Indicator) pin on the transceiver will supply an analog voltage proportional to the signal strength [23]. This will allow comparison of the voltage level to a predetermined level so that if necessary the data line can be squelched to save power if the signal strength falls below a certain level. Once again the A/D pin choice is flexible since the others can also be used as general I/O, however pin 22 was chosen simply because it was next to three other general I/O pins. Lastly the four input capture pins on the microcontroller will be used to capture the input from the IR phototransistors. All other connections are done through general I/O and there are many other I/O pins available left over to bring out to a header in case of a pin failure. Table 8.3.1 shows all of the microcontroller pin connections to each peripheral.

8.4 Summary

Due to the simplicity of the project there were not any major design issues, however several design considerations included picking the right transistor and resistors for the three types of LEDs, which pins of the microcontroller were required by each peripheral. The basic theory of operation is that when pushbutton trigger is depressed, the microcontroller sends a signal to the IR diode (one or both depending on the game mode). Upon the detection of a hit by the IR phototransistor, a RF signal is transmitted to the base station to register the hit. The base station then sends out a signal to the ‘hit’ vest to deactivate color LEDs and IR LED, and also sends a signal to display the hit on the LCD screens of both the guns while also displaying the hit on the base station LCD screen. After a period of time the base station will send another RF signal to reactivate the hit vest. A keypad is attached to the base station to enable users to select game modes. The major subsystems of the microcontroller that are used are the SPI, PWM, A/D, and input capture.

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Table 8.3.1: Microcontroller connections for the Base and Guns

Base Microcontroller Portable Microcontroller

External Device FunctionPin # External Device Function

Pin #

Programming Header PGC clock input 1 Programming Header PGC clock input 1

PGD - data input/output 44

PGD - data input/output 44

/MCLR - Master Reset 18 /MCLR - Master Reset 18 VDD 40 VDD 40 VSS 39 VSS 39Shift Register SDO1 - SPI Data out 44 Shift Register SDO1 - SPI Data out 44 SCK1 43 SCK1 43LCD Screen RF1 - LCD Enable 4 LCD Screen RF1 - LCD Enable 4 RF0 - Register Select 5 RF0 - Register Select 5Key Encoder RE4 - output enable 9 RF Transceiver AN3 - RSSI 22 RE3 - Data out D 10 RB0 - Data 19 RE2 - Data out C 11 RB1 - T/R Select 20 RE1 - Data out B 14 RB2 -Power down 21 RE0 - Data out A 15 Trigger RE5 - trigger input 8 IC7 - Data Available 23 IR LED PWM1H 14RF Transceiver AN3 - RSSI 22 IR LED 2 PWM2H 10 RB0 - Data 19 Laser LED RE4 - Gen I/O 9 RB1 - T/R Select 20 Color LED Set 1 RB6 - Gen I/O 25 RB2 -Power down 21 Color LED Set 2 RB7 - Gen I/O 26

Photo Transistor Set 1 IC1 - input capture 42Photo Transistor Set 2 IC2 - input capture 37Photo Transistor Set 3 IC8 - input capture 24Photo Transistor Set 4 IC7 - input capture 23

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9.0 PCB Layout Design Considerations

9.1 Introduction

Our project of Laser Tag requires two different types of PCB designs. One design is for an arbitrary gun/vest pair. This PCB must fit in the gun package, which is a modified water gun. The board must fit inside the water tank, and the headers must be placed where they can be easily reached by cables coming from outside the tank. The second PCB design is for the base station. It is much less constrained because there are no requirements for the size of box that it must fit in. However, it contains many of the same components as the gun PCB, and therefore will use a similar size and part placement for simplicity. The primary difference between the two PCBs is that the base station has a keypad decoder with a header for the keypad, whereas the gun has transistors to drive the LEDs and a header to route signals to the vest. The rest of this document will focus on design considerations that are held in common by both designs, as the parts they have in common provide the most significant constraints.

9.2 PCB Layout Design Considerations – Overall

The portion of our PCB that has the most constraints unique to our design is the RF transceiver. As its operating frequency is obviously in the RF range, it is a significant source of noise in the circuit. Also, as the only analog IC on our board, it is the most susceptible to external noise. Fortunately, all of the problems inherent in using this chip can be mitigated or eliminated with a single solution. That solution is to have a large ground plane below the chip on the opposite side of the board. Ground planes are commonly used to reduce the impact of noise in any type of circuit, and the data sheet for our transceiver chip specifically requires a large ground plane below the RF chip [27]. The ground plane also serves as the second pole of the RF antenna, thereby improving its performance. For this purpose, the data sheet says that the ground plane should ideally have a surface area no less than the length of the ¼-wave antenna.

The other constraints specific to our transceiver chip regard trace routing. First and foremost, we cannot have any traces routed underneath and on the same layer as the chip. [27] This is simply because the chip has exposed traces on its underside, and any traces on the board could easily cause a short circuit in the chip. Also in the realm of routing, the data sheet requests that three particular pin traces be kept as short as possible. These are the two ground pins and the antenna pin. The ground pins should only be long enough to reach past the soldered pin to a via which links directly to the ground plane. This way the ground impedance is kept to a minimum, which further reduces noise. The trace from the chip to the antenna should be kept short in order to minimize the impact of the trace on the characteristics of the antenna, which is simply a wire of a particular length tuned for the transmission frequency. Any extra length in the trace beyond what

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is necessary for physical part spacing could detune the antenna, causing communication problems. These routing concerns will have to be addressed manually, after the auto-router does the first pass on the board.

9.3 PCB Layout Design Considerations – Microcontroller

Our microcontroller has no placement or routing requirements specific to our chip. One consideration is that it should be placed reasonably centrally on the board in order to obtain the simplest routing, since pretty much everything is connected to it. It cannot be placed in the physical center of the board, as the RF chip and ground plane will be taking up about half of the board, but we can certainly place it such that the other components are around it and near the pins they connect to.

Another thing that we need to take into account is that we need five particular pins to be brought out to a header for in-circuit programming. [28] Since at least one of these pins is also needed for another purpose, we need to make sure that the two uses of these pins are electrically isolated, using a resistor. We won’t have a problem with two things trying to drive the pins, since we won’t be programming the microcontroller when it’s in use. However, we do need to make sure that the programmer doesn’t affect whatever else may be connected to the pins. Of particular concern are the two pins that the programmer uses to send data to the microcontroller. If left unchecked, these could potentially send commands to another chip, or try to drive an output, or any of a number of disastrous possibilities.

9.4 PCB Layout Design Considerations - Power Supply

We plan on using standard D-cell batteries for our power supply, so we don’t have to worry about noise from an AC power source or ripple due to imperfect filtering. The most important consideration for the power section of our circuit is keeping the RF system reasonably isolated from the rest of the circuit. As was noted earlier, the RF transceiver is expected to be our most significant source of noise. We will be keeping it isolated by ensuring that the ground plane for the transceiver is connected to the ground for the rest of the system at only one point, and also by not placing any other parts above the RF ground plane.

In addition to the required ground plane under the RF transceiver and antenna, it would be useful to place ground planes under some of the other chips, especially the microcontroller. The microcontroller will be running at a clock rate of only a few MHz—two orders of magnitude below the frequency of the RF transceiver—so it’s not as critical as the RF ground plane. However, any amount of noise reduction will help to ensure the stability of our circuit. Also,

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having a ground plane under the microcontroller would allow us to connect the ground pins of the chip with short traces and vias directly to the ground plane, which will lower the impedance of the power circuit.

9.5 Summary

The most significant considerations for our PCB design come from requirements of the RF system. There needs to be a large ground plane under the RF transceiver and antenna, and there can be no traces directly under the transceiver chip. The microcontroller has few restrictions specific to our chip. It should be placed centrally among the other components for optimal routing, and needs five pins for in-circuit programming to be electrically isolated from any other use they might have. The restrictions on the power circuit primarily involve electrical isolation of noisy components. The RF system has the most potential for noise, with a transmission frequency on the order of 100 MHz. The microcontroller is the next noisiest chip with a clock rate on the order of 1 to 10 MHz, and all other signals are expected to switch at less than 1 MHz.

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10.0 Software Design Considerations

10.1 Introduction

The software for the Quazyx system is similar to any other laser tag system including infrared transmission and sensing, LCD displays, keypad configuration, and button-triggered firing mostly based on interrupts for near real-time operation. However, Quazyx includes radio frequency communication between the portable gun packs and the base station for live game statistics and game enhancements like an invincibility mode that require the use of messaging queues, collision-detection protocols, and coordinated timing within the software. This section will detail the software design considerations and the architecture of the code modules that make Quazyx operate.

10.2 Software Design Considerations

Within the Quazyx software project, all of the detailed memory mappings and addresses for data registers and configuration are handled by the Microchip C30 compiler and the dsPIC30F4011 header that is imported upon compilation. This header file allows the use of the pin names with an underscore prefix for reading and writing within the C code and abstracts the exact address and structures of the microcontroller memory. The mappings of the utilized peripherals to their respective port pins and underscore-prefixed variable names can be seen in Table 10.2.1 below. During the build process, the C30 compiler reports program memory in flash starting at 0x100 with strings followed by application code and ending with initialization routines. Data memory utilizes 0x000 through 0x800 for the heap and 0x804 through the end of SRAM for the stack. The addresses overlap because the PIC uses separate instruction and data memories. See the dsPIC30F reference manual for register name and memory address details [29].

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Table 10.2.1: Variable Name to Pin and Peripheral Mapping

Base Portable

External Device Variable Name - Function Pin External Device Variable Name - Function Pin

Shift Register _SDO1 - SPI Data out 44 Shift Register _SDO1 - SPI Data out 44

_SCK1 43 _SCK1 43

LCD Screen _RF1 - LCD Enable 4 LCD Screen _RF1 - LCD Enable 4

_RF0 - Register Select 5 _RF0 - Register Select 5

Key Encoder _RE4 - output enable 9 RF Transceiver _AN3 - RSSI 22

_RE3 - Data out D 10 _RB0 - Data 19

_RE2 - Data out C 11 _RB1 - T/R Select 20

_RE1 - Data out B 14 _RB2 -Power down 21

_RE0 - Data out A 15 Trigger _RE5 - trigger input 8

_IC7 - Data Available 23 IR LED _PWM1H 14

RF Transceiver _AN3 - RSSI 22 IR LED 2 _PWM2H 10

_RB0 - Data 19 Laser LED _RE4 - Gen I/O 9

_RB1 - T/R Select 20 Color LED Set 1 _RB6 - Gen I/O 25

_RB2 -Power down 21 Color LED Set 2 _RB7 - Gen I/O 26

Photo Transistor 1 _IC1 - input capture 42




The peripherals utilized include SPI, timer, input capture, PWM, and general purpose I/O. Initializing the SPI for connection to the shift register requires modifying the SPI1CONbits structure to set the data rate, trigger clock edge, word size, and framing/checksum options. Then the SPI is operated simply by filling the SPI1BUF variable and checking the status within the SPI1STATbits structure. The interrupt must also be set by filling the _SPI1IE register with 1. The timer module operates similarly using the T1CONbits structure (for timer 1 with other timers replacing 1 for their respective value) to set up the tick rate and configuration settings, clearing the TMR1 register containing the current timer count, setting the PR1 register for the value to trigger an interrupt on, and setting that interrupt by filling the _T1IE register. For the input capture module, the IC1CONbits structure is used to set up interrupts as well as trigger edge for the input pin. The PWM, used to control the infrared shot pulse, is configured first by setting a time base in the PTCON register that all PWM channels share, then adjusting the individual PWMCON control and PDC duty cycle structures for each channel. Lastly, all general purpose I/O pins are easy to set up using their respective _TRIS and the values for input or output can be manipulated with the _R variables. The only notable issue with general purpose I/O is that for any pin that shares input with the ATD module (most of the B section pins), an

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additional set of flags within the PCFG register controls whether those pins connect to the ATD or digital input and must be set accordingly.

The overall organization of the application code centers around interrupts with a small polling loop responsible for the processing of the message queues after the initialization sequence. This organization was chosen as it allows the microcontroller to react in near real-time to human input. The messaging queues are established and placed within a polling loop containing a delay. In the case of the LCD panel, this messaging queue and delay prevents multiple interrupts from sending messages to the panel too quickly for the user to see and potentially covering up one message with another. In the case of the RF communication, the messaging queue allows our RF protocol to process actions in a well-ordered manner and leave a message in the queue for later retry if a collision or corruption error occurs in transmission.

Collisions are detected when a corresponding acknowledgement packet is not received within approximately 500ms of the initial transmission of the data packet. If no acknowledgement is received, a random number is pulled from the random number generator and used as the delay before retrying the transmission. The random retry reduces the chance of another collision.

For debugging the application, standard 6-pin Microchip programmer/debugger headers have been attached to both the gun and base station PCBs [30]. The chosen microcontroller has a memory resident debugging area supporting two hardware breakpoints and interaction with the MPLAB development environment for execution trace and memory inspection. Additionally, for debugging RF communication, the raw analog signal from the RF chip has been mapped to an ATD port on the microcontroller which can be initialized and read through the Microchip debugger if necessary. With a combination of these resources, the LCD display panel, and the various LEDs attached to the device, the code can be easily debugged. Specific extra routines that are commented out in the final production code were used to output the RF communication packets directly to the LCD display when they were sent or received to help debug that communication and similar routines exist for the IR modules.

10.3 Software Design Narrative

The overall architecture of the Quazyx software consists of a main loop and a handful of interrupts. Generally, the main loop on top initializes the various wrapper modules and interrupts, the wrappers initialize their respective device drivers and processor peripherals, then the machine moves into the main polling loop state where interrupts drive most of the reactions back up through the main class and down into whichever module needs to respond to the request.

The main polling loop for the base station provides a menu system to set up operation of the laser tag game. It prompts first for the length of the game then the type of game before waiting for the

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various gun/vest modules to register with the RF module. Once registration is complete, the loop proceeds to prompt for game start, counts down for 30 seconds, and then sends the command to the guns to begin the game with the specified mode. The base station then proceeds to keep track of the current game time with a broadcast of the remaining time every minute to update the individual pack displays. Additionally, when shots are fired or a player is hit, the main polling loop continues to update the LCD panel at the base to allow the game administrator to see what is going on. At any time during the game, this loop can be escaped through a cancel game button. When the game ends, the main loop will rotate through all collected statistics on all the players. On the press of any button, the loop will restart from the top at game time and type selection.

For the portable gun modules, the main loop provides no real menu system as the operation of the game is primarily controlled by the base. Once a gun is turned on, the loop will wait for the signal from the base station to begin negotiating registration of the pack. Afterward the loop blocks until the game start message is received including game type and time remaining information. Then the loop simply serves to watch the hit and kill count of the player and give out power-ups according to game rules if the power-ups were turned on. Power-ups include an invincibility mode that is given out after five kills in a row, a continuous fire mode given out after five deaths in a row, and an invisibility mode given out based on when the random number generator passes the threshold of 121. This segment of the code will end when the game end message is received over RF and will proceed to display the player’s game statistics until a new game message is received and the loop starts again.

The RF and LCD messaging modules both provide synchronous send routines that will pass the given message directly out their respective ports to the hardware. In the case of the RF module, receipt of packets happens within an interrupt. The packets use NRZI encoding to keep the line switching. The general packet format starts with a USB-style start byte in NRZI, followed by the destination ID, source ID, command type, and up to four bytes of payload data. As such, the interrupt can escape early if it detects a bad start byte or if the destination byte does not match the ID of the pack that is currently receiving data.

The Timer software module provides support for other functions such as the LCD driver. It is set up to allow other routines to request a specific synchronous “wait” period of time when set-up and hold times in communication with peripherals need to be met. This module has been implemented with the help of online source code [31] and tested in hardware. A second timer is used to sample one of the ATD pins to generate random numbers. A third timer is implemented much like the first to delay for multiples of 1 ms for the RF module and IR communication routines.

The LCD, Keypad, IR, RF, and PWM wrapper classes provide higher level commands such as writing or reading of entire lines of data and overall initialization routines. Individual character,

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byte, or bit level transfers are abstracted away within the wrappers or down one level in the device drivers. IR routines are transmitted and received in a similar way to the RF modules and use the same start byte and packet structure. However, no acknowledgement is returned. The sending side simply continues to resend the packet until the trigger is released or the trigger time out occurs (500 ms). The receiving side will deactivate the entire gun pack when it matches a hit from a valid player and therefore will not accidentally record too many hits if one were to focus the transmission on one player for the whole firing period.

Lastly, the specific SPI, input capture, PWM, and general purpose I/O device drivers contain all the control bits, registers, and operational flags that are necessary to activate those microcontroller peripherals and establish a properly timed connection over the link. These modules accept only the most basic bit or byte input and output commands and map them to the registers and timings required by the interface.

10.4 Summary

This software design section for the Quazyx Laser Warfare System contains an overview of the design considerations in terms of Flash and SRAM utilization, pin to register mapping within the code, the utilized microcontroller peripherals and their respective setup and operational registers, and the overall architecture of the Quazyx code. A main polling loop is responsible for a small portion of outgoing functionality for the RF communication and LCD panel display as well as the main game logic for power-ups and menus systems while interrupts from the SPI, input capture, RF, and timer drive a majority of the actions and responses to user input. Device drivers exist for most off-chip peripherals and wrappers create convenience functions for the main program logic in manipulating strings, initializations, and multi-byte messages. Debugging and support is provided by the MPLAB development environment packaged with the microcontroller and available in-circuit through a standard set of header pins in combination with the connected LEDs and LCD panel display. Lastly, protocols for IR and RF communication are based on a USB frame for each packet and retry on random intervals when acknowledgement is not received to detect and alleviate collisions. Software source files can be found as a part of the source code submission ZIP file.

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11.0 Version 2 Changes

In a second revision of this product, revisions would be made to the PCB, sensor pod modules, and power circuitry. All other components functioned as expected and would be reused as is in a second revision.

One of the major issues during assembly and debugging of the gun/vest modules was the amount of off-board components that required fly-wired power lines as well as pull-up resistors. On the original PCB, only signal lines are provided for the trigger, LEDs, laser, and connection to the vest pack via Ethernet. As such, the 4.5V power to each of these had to be tapped using fly-wires from the battery lugs directly. In a revision, the power traces would be placed on the PCB and additional header pins would be added such that a single simple cable could be made to connect to each of these devices.

For each of the sensor pods, we believed that it would be easiest to use perfboard segments and assemble the LEDs, phototransistors, and various wiring to interconnect the modules. However, after the creation and connection of four modules per sensor vest, we realized that it would have been much easier to create another PCB that simply had several copies of a sensor pod layout and mount the LEDs and phototransistors to these PCB segments. Also, it would have significantly helped reduce our wiring headaches in respect to cross-over phone and Ethernet cables if we had proper PCB headers and joined the correct wires as traces on the board.

Lastly, one critical issue we worked around was the lack of power regulation on our board. In the end, the entire system operated properly without any regulators after disabling the brown-out functionality of the microcontroller and reducing the clock rate. However, in a discussion with course staff, we would place a buck-boost converter on the PCB in a second revision to properly regulate 3.3V and 4.5V power. This would likely eliminate the need to disable the brown-out reset and allow more power to be drained from the batteries before the system would turn off due to low voltage.

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12.0 Summary and Conclusions

Through the course of this project, we successfully built a working laser tag system to the specifications of our initial idea. With the system, a game of laser tag can be played successfully and contains all the power-up, statistics, and radio frequency communication specifications we initially envisioned.

Along the way, we learned several new skills and refined many existing ones from previous courses and experience. It was our first experience designing and laying out a printed circuit board, working with wireless communications technologies, and using a battery powered circuit. Additionally, in the past we only had experience with programming microcontrollers in assembly, so the introduction of Microchip C30 allowed us to develop faster while still understanding how the code turned into assembly. We also gained experience in how interrupts get triggered and their priorities. Also, we learned lessons about power regulation, crystal oscillators, and cabling.

In terms of the senior design curriculum, we also gained new insight into all the considerations that must go into the creation of an integrated digital system. We learned about the workings of the patent system and its implications on digital design, the importance of environmental considerations in the selection of components and fabrication, and how to identify potential safety and reliability issues with a product. As a team, we strengthened our skills of delegating tasks to one another and learned to find productive tasks that would help the team when we individually came to moments of free time.

Overall, our digital systems senior design project was a great developmental experience for our team. We believe that our success in carrying the project through all phases from design to completion proves both our success in our undergraduate studies and certifies our ability to do real world engineering work or future graduate study in our coming years.

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13.0 References

[1] “dsPIC30F4011 Data Sheet,” dsPIC30F4011, Microchip Technology, Inc., July 4, 2008. [Online]. Available: http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010337. [Accessed: Feb. 1, 2010].

[2] “Energizer E95 Product Datasheet,” E95, Energizer Holdings, Inc. [Online]. Available: http://data.energizer.com/PDFs/E95.pdf. [Accessed: Feb. 2, 2010].

[3] “Amazon.com: Laser tag: Toys & Games,” Amazon.com Search, Amazon.com, Inc., Feb. 4, 2010. [Online]. Available: http://www.amazon.com/gp/search/ref=sr_nr_i_0?rh=i%3Atoys-and-games%2Ck%3Alaser+tag&keywords=laser+tag&ie=UTF8&qid=1265343253. [Accessed: Feb. 4, 2010].

[4] “Laserforce Packages,” Laserforce – Professional Laser Tag Systems, Laserforce, Inc. [Online]. Available: http://www.laserforcetag.com/packages. [Accessed: Feb. 1, 2010].

[5] “dsPIC33FJ32GP302/304, dsPIC33FJ64GPX02/X04 and dsPIC33FJ128GPX02/X04 Data Sheet,” dsPIC33FJ32GP320, Microchip Technology, Inc., Nov. 19, 2009. [Online]. Available: http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en532305. [Accessed: Feb. 2, 2010].

[6] “Low-Power Sub-1 GHz RF Transceiver,” CC1100, Texas Instruments, Inc., 2009. [Online]. Available: http://focus.ti.com/lit/ds/symlink/cc1100.pdf. [Accessed: Feb. 2, 2010].

[7] “PLL Tuned UHF Transceiver for Data Transfer Applications,” MC33696, Freescale Semiconductor, Inc., Mar. 2009. [Online]. Available: http://www.freescale.com/files/analog/doc/data_sheet/MC33696.pdf. [Accessed: Feb. 2, 2010].

[8] “LT Series Transceiver Module Data Guide,” Linx Technologies Wireless Made Simple, Linx Technologies, Inc., Feb. 28, 2008. [Online]. Available: http://www.linxtechnologies.com/Documents/TRM-xxx-LT_Data_Guide.pdf. [Accessed: Feb. 1, 2010].

[9] S. Bull and T. Svoboda, “Electronic Tag Game,” U.S. Patent 6,530,841, June 26, 2001. Available: http://www.freepatentsonline.com/6530841.html

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http://www.freepatentsonline.com/6530841.html

http://www.linxtechnologies.com/Documents/TRM-xxx-LT_Data_Guide.pdf

http://www.freescale.com/files/analog/doc/data_sheet/MC33696.pdf

http://focus.ti.com/lit/ds/symlink/cc1100.pdf

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en532305


http://www.laserforcetag.com/packages

http://www.amazon.com/gp/search/ref=sr_nr_i_0?rh=i%3Atoys-and-games%2Ck%3Alaser+tag&keywords=laser+tag&ie=UTF8&qid=1265343253



http://data.energizer.com/PDFs/E95.pdf




[10] Kwan et al., “Interactive light-operated toy shooting game,” U.S. Patent 5,741,185, February 5, 1997. Available: http://www.freepatentsonline.com/5741185.html

[11] Small et al., “Electronic game with infrared emitter and sensor,” U.S. Patent 5,904,621, January 16, 1998. Available: http://www.freepatentsonline.com/5904621.html

[12] Military Handbook: Reliability Prediction of Electronic Equipment, MIL-HDBK-217F. 1991.

[13] “dsPIC30F4011 Data Sheet,” dsPIC30F4011, Microchip Technology, Inc., July 4, 2008. [Online]. Available: http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010337. [Accessed: Apr. 8, 2010].

[14] “LT Series Transceiver Module Data Guide,” Linx Technologies Wireless Made Simple, Linx Technologies, Inc., Feb. 28, 2008. [Online]. Available: http://www.linxtechnologies.com/Documents/TRM-xxx-LT_Data_Guide.pdf. [Accessed: Apr. 8, 2010].

[15] “Don’t aim laser pointers at a person’s head and eyes!” LaserPointerSafety.com. [Online] Available: http://www.laserpointersafety.com/laser-hazards_head-eyes/laser-hazards_head-eyes.html. [Accessed: Apr. 5, 2010].

[16] “Consumer Safety Alert: Internet Sales of Laser Products” Food and Drug Administration, March 2, 2010. [Online]. Available:

http://www.fda.gov/Radiation-EmittingProducts/RadiationSafety/AlertsandNotices/ucm116534.htm . [Accessed: April, 16, 2010].

[17] “Illuminating Facts About Laser Pointers” U.S. Food and Drug Administration, May 20, 2009. [Online]. Available: http://www.fda.gov/Radiation-EmittingProducts/RadiationSafety/AlertsandNotices/ucm153548.htm . [Accessed: April 16, 2010].

[18] “Call to Recycle: Frequently Asked Questions” Verizon Wireless, 2010. [Online]. Available: http://www.verizonwireless.com/b2c/aboutUs/communityservice/recycleFaqs.jsp#q4. [Accessed: April 16, 2010].

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http://www.verizonwireless.com/b2c/aboutUs/communityservice/recycleFaqs.jsp#q4

http://www.fda.gov/Radiation-EmittingProducts/RadiationSafety/AlertsandNotices/ucm153548.htm




http://www.laserpointersafety.com/laser-hazards_head-eyes/laser-hazards_head-eyes.html

http://www.laserpointersafety.com/laser-hazards_head-eyes/laser-hazards_head-eyes.html







[19] “LaserTron,” 2008. [online] Available: http://www.laser-tron.com/index.htm [Accessed Feb 8, 2010]

[20] “Humvee Combat Black Tactical Vest,” Aug. 7, 2008. [online] Available: http://www.amazon.com/Humvee-Combat-Black-Tactical-Multi/dp/B000PUFSLG [Accessed Feb. 8, 2010]

[21] “Project Boxes,” 2010. [online] Available: http://www.radioshack.com/family/index.jsp?categoryId=2032276 [Accessed Feb 8, 2010]



[24] “NHD‐0224BZ‐FL‐GBW Data Sheet,” NHD‐0224BZ‐FL‐GBW, Newhaven Display Intl, Inc., December 21, 2009. [Online]. Available: http://www.newhavendisplay.com/specs/NHD-0224BZ-FL-GBW.pdf . [Accessed: Feb. 18, 2010].

[25] “MM74HC164 Data Sheet,” MM74HC164, Fairchild Semiconductor, Inc., Feb, 2008. [Online]. Available: http://www.fairchildsemi.com/ds/MM/MM74HC164.pdf . [Accessed: Feb. 18, 2010].



[28] “PICkit 2 Programmer/Debugger User’s Guide,” Microchip Technology, Inc., January 2, 2008. [Online]. Available:

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http://www.fairchildsemi.com/ds/MM/MM74HC164.pdf

http://www.newhavendisplay.com/specs/NHD-0224BZ-FL-GBW.pdf




http://www.radioshack.com/family/index.jsp?categoryId=2032276

http://www.radioshack.com/family/index.jsp?categoryId=2032276

http://www.amazon.com/Humvee-Combat-Black-Tactical-Multi/dp/B000PUFSLG

http://www.laser-tron.com/index.htm


http://ww1.microchip.com/downloads/en/DeviceDoc/51553E.pdf. [Accessed: Feb 25, 2010].

[29] Microchip Technology, Inc., “dsPIC30F Family Reference Manual,” Microchip Technology, Inc., 2005. Available: http://ww1.microchip.com/downloads/en/DeviceDoc/ 70046D . pdf . [Accessed: Feb. 27, 2010].

[30] Microchip Technology, Inc., “PICkit 2 Programmer/Debugger Users Guide,” Microchip Technology, Inc., 2008. Available: http:// ww1.microchip.com/downloads/en/DeviceDoc/51553E.pdf . [Accessed: Mar. 25, 2010].

[31] Btbass, “Delay and Timeout Routine for dsPIC in Hi-Tech dsPICC,” EDAboard.com Forum, 2009. Available: http://www.edaboard.com/ftopic371067.html. [Accessed: Mar. 23, 2010].

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http://www.edaboard.com/ftopic371067.html

http://ww1.microchip.com/downloads/en/DeviceDoc/51553E.pdf

http://ww1.microchip.com/downloads/en/DeviceDoc/70046D.pdf

http://ww1.microchip.com/downloads/en/DeviceDoc/51553E.pdf


Appendix A: Individual Contributions

A.1 Contributions of Ben Moeller:

At the beginning of the semester, Ben spent most of his time developing a method to communicate IR light over long distances. This included tracking down high powered IR LEDs and sensitive receiver modules. One issue with IR transmission is filtering out IR noise. Normal IR detectors are in an LED package and act as an IR phototransistor. These are very sensitive to noise and were not a feasible solution to the IR communication problem. Ben ended up tracking down some IR detection modules which are also very sensitive but only detect IR when pulsed at 56kHz. This eliminated the possibility of IR noise and still allowed the detection system to be extremely sensitive. Ben also designed a barrel design which had a lens at the end to focus the IR light and greatly improve the transmission range.

Since he was mainly responsible for the packaging design, Ben purchased plastic guns from Wal-Mart to use as the main gun housings. Over the course of the semester, he modified these guns to accommodate for all of the off-board electronic components such as IR LEDs and the LCD screens. Additionally, the guns were modified to house the gun-vest PCB and batteries. Ben also purchased a RadioShack project box to act as the base station. He designed a layout for the off-board electronics and manipulated the project box to hold these as well as the base PCB and batteries.

Of the team members, Ben had the most soldering experience. Thus, he was mainly responsible for the assembly of the PCBs and creation of cables for the system. Several cables were necessary for the interconnection of off-board electronics with the PCB. For example, both guns and the base station have an LCD screen that needs to be connected to the PCB. This required the creation of three 16-conductor cables.

Additionally, Ben assisted in hardware troubleshooting when problems arose. Half-way through the semester, Mike realized that, though the datasheet for the LCD screen said it would operate at 3V, it was not functional at this voltage. This required a change in the voltage supplied to the LCD screen so PCB traces needed to be cut and fly-wired to the 4.5V rail. Ben performed these modifications, as well as a few others that occurred during the design and debugging phases of the project.

Lastly, Ben was responsible for the packaging design homework as well as the patent liability analysis homework.

A-1


A.2 Contributions of Emily Blount:

When the project first started Emily helped to review the part selection and choose the final components. As an EE the team looked to Emily’s experience to verify whether the parts would work well together. Once Emily had reviewed Mike’s choice on the parts she was responsible for ordering the components, except the RF module, the PIC microcontroller, and the IR LEDs and detector modules.

Next Emily was responsible for the schematic drawing. This was a very important part, and since Emily wanted to be sure she connected the parts correctly, Emily asked the team to help her determine connections on tricky parts like the RF module and keypad to keypad encoder. Emily decided how the trigger would be implemented, and how the vest and gun LEDs would be controlled. It was really helpful to finally see how every peripheral would connect together and Emily believes this solidified what the team thought what the project would finally look like.

Once the schematic drawing was finalized, Emily started designing the vests. Since Emily is the only team member who owns a sewing machine and knows how to use one she volunteered to make the vests. This involved many trips to the fabric store to get various parts, first the fabric, then the snaps, straps, buckles, and Velcro that we eventually decided to use. Since making something from scratch is no easy process, the implementation of the vests actually took quite a bit of Emily’s time. However, she still spent time in the lab working on the electrical hardware implementation.

This involved designing the vests sensor pods. Emily split this task into two parts, first was the LED implementation, and second was the detector module implementation. Inside each sensor pod for the LED implementation are two transistors, 4 LEDs, 4 resistors, 2 power rails, and four wires going off board for power, ground, and the base of each transistor. For the detector module portion, there were three detector modules, one capacitor, one resistor, a signal rail that connected to all three detectors and went off board with a wire, and finally a ground rail that also connected to all three detectors. All of these parts on the tiny copper perfboard required careful planning and could get quite messy, as evidenced by Ben’s first iteration. It also did not help that between the vests, the perfboard was different and the copper design covered different holes. Therefore, not only did the sensor pods have to be designed once, but again for the other perfboard. Emily took the perfboard from the ECE402 design lab, so we couldn’t be choosy about the kind that we got.

The pods also required some kind of packaging, so Emily took a trip to Target to shop for a clear plastic box that would be just large enough to house the sensor pods. Emily ended up choosing a travel case for Q-tips, picked up eight of them, and drilled holes in the sides so that the wires could leave the boxes while they housed the sensor pods.

A-2


Then once the sensor pods were designed and implemented, eight in total which amounted to a lot of soldering and repetition, the signal lines leaving each sensor pod had to be connected together in a feasible way to go to the gun PCB. It was a question of what kind of cable would make it relatively easy to connect all of the sensor pods together, and it was decided that a 6 line telephone cable would be appropriate. Emily bought 3 12ft male-to-male telephone cord, cut them in half and soldered the five signal lines from each sensor pod to the same wire color of the telephone cord. To tie the pods together Emily wired three female ports together to pass the signals to an 8wire Ethernet cable that went to the gun PCB.

After that was completed, Emily was a resource for any hardware troubleshooting. All throughout the project she also updated the website, and compiled and edited any team written assignments, except for this one, together.

A-3


A.3 Contributions of David Freidin:

David’s most significant contribution in the first half of the semester was the PCB design. Working from the basic schematic that Emily made, he made a new schematic containing only the parts that were to go on the PCB. This also included creating a new part footprint for the antenna, which had not been made for the main schematic. After trying out the auto-routing tool with various settings, he learned how to manually route and lock traces to accommodate the specific requirements of the RF transceiver and antenna, and to make wide power and ground rails. Then, after auto-routing the rest, he went through and fixed all of the acid traps and sub-optimal routing made by the software. When the time came to prepare the final layout for fabrication, it took a few tries to fix the problems brought up by the online design checker.

In the second half of the semester, David’s major focus was on various aspects of the software development. He was primarily responsible for the design and implementation of both the RF and IR communication protocols. He started by coming up with a rough design for the RF protocol, based on things he had learned in the previous semester in ECE 469. After discussing various ideas with Michael, he also decided on an IR protocol based on pulse length, since only one number needed to be sent via IR. He then started to implement the RF protocol in software, and when the first PCB was populated the code was tested. After some major debugging of various parts of the code, a simple string of “Hello!” was successfully encoded and transmitted. Once the second PCB was populated, the receiving code could be tested, and eventually the message was properly received and printed on the LCD panel. After more coding and debugging, a slightly revised version of the RF protocol was implemented and working reliably.

At this point he turned his attention back to the IR communication. His original idea of encoding the pack ID in the pulse width of the IR signal was fairly simple to implement, but proved fairly unreliable in practice, due to the unpredictable nature of the other interrupts, and the lack of any way to differentiate between data and noise. A decision was reached to rewrite the IR protocol to be similar in concept to the RF protocol, though much simpler. This was quickly implemented and tested, and it worked with no significant issues.

Throughout the whole semester, David also contributed in various ways to the rest of the project. Based on the constraints determined by the team, he picked an appropriate microcontroller which has worked without any problems. He also helped check over the schematic and proofread homework for other team members. He assisted in determining pin assignments for the microcontroller, and in soldering one of the PCBs. He wrote the homework assignments on the PCB design and on the reliability & safety analysis, and also contributed to all team papers and presentations.

A-4


A.4 Contributions of Michael Niksa:

Michael’s contribution during the first half of the semester started with sketching out the general overview of the design, required components, and interaction of the components that would be necessary to implement laser tag. This was primarily driven by the component selection and design analysis that Michael completed in the first few weeks of the semester. After this homework, Michael switched tasks from broad design to a specific research into radio frequency.

For the radio frequency component of the product, Michael researched various different vendors within the Wi-Fi product field before coming to the conclusion that Wi-Fi would likely be too expensive and unnecessary for the laser tag system. Then, from a featured posting on Digi-Key, Michael found a company called Linx Technologies that had complete systems to “make anything wireless.” Through phone calls with an engineer at Linx Technologies, Michael established the components that would be necessary to successfully integrate the wireless component of the project including a transceiver module, the proper antennas, and a general overview of how to make an effective communications protocol.

Prior to spring break, Michael assisted with the design of the schematic and PCB for the gun/vest and base station modules. This included detailed tracing of signals on David’s PCB layouts prior to fabrication to catch any errors. In terms of the schematic, Michael assisted Emily with deciding which pins on the microcontrollers were to be connected to various off-board peripherals as well as the various on-board ICs. Also, Michael worked on cleaning up, updating, and organizing the various block diagrams and documentation required for the midterm design report.

Once the DIP versions of the microcontroller, shift register, and other ICs arrived, Michael worked on putting together the initial prototype of the laser tag system on a breadboard. With this prototype, the initial low-level drivers were written and tested in a limited fashion. Also during this time, Michael worked with Ben to develop a system of reliably transmitting infrared signals using high powered IR LEDs and special sensor modules that would only detect a very specific frequency (56kHz) of IR signal.

Then after the spring break/midterm report time, Michael focused on further developing and testing the low-level drivers that would support communication and display for the main game logic code. A part of this included the completion of the software design analysis homework where the specific configuration variables of necessary microcontroller peripherals were researched, the overall code architecture was designed, and diagrams were created corresponding to architectural decisions.

A-5


Afterward for the remainder of the semester, Michael worked with David to develop and test the code within the final PCBs as they were assembled. Michael also found several issues with components such as 4.5V required on LCD panels and a difficulty with triggering. Michael involved Ben to assist with fly-wiring the PCB to accommodate these issues and successfully alleviate technical difficulties. After ensuring the stability of all low-level drivers, Michael assisted David with software debugging and, when necessary, cooperated with Emily and Ben in the continued debugging and refinement of the sensor modules and gun components.

Overall, Michael’s work focused on software emphasizing the low-level interaction with various ICs and off-board components. Foremost among these was extensive research and understanding of radio frequency communication and the necessary design constraints. Then in addition to assisting with debugging of hardware and higher level code, Michael served as a resource to consult on the design constraints of the project and assisted in making modifications when necessary. Lastly, Michael’s homework assignments were the Design Constraints Analysis and the Software Design Considerations documents as well as the assembly of the final presentation and this report document from the individual group member contributions.

A-6


Appendix B: Packaging

Figure B.1 – Commercially produced squirt gun housing

Figure B.2 – CAD drawing of vest and sensor pod mounting

B-1


Figure B.3 – CAD drawing of base station and peripheral mounting

B-2

ECE 477 Final Report Spring 2010

Appendix C: Schematic

Figure C.1 – Final Base Station Circuit Schematic

C-1


Figure C.2 – Final Gun/Vest Circuit Schematic

C-2


Figure C.3 – Sensor Module Schematic

C-3


Appendix D: PCB Layout Top and Bottom Copper

Figure D.1 – Base Station PCB Top and Bottom with Silkscreen

Figure D.2 – Gun PCB Top and Bottom with Silkscreen

D-1


Appendix E: Parts List SpreadsheetVendor Manufacturer Part No. Description Unit Cost Qty Total Cost

Digi-Key Microchip DSPIC30F401130IPT-ND

44-pin TQFP 16-bit Microcontroller 7.06 3 $21.18

Digi-Key Linx Technologies, Inc.

LICAL-TRC-MTCT-ND

20-pin SSOP Bi-directional radio frequency transcoder

4.15 3 $12.45


TRM-418-LT-ND 418Mhz RF transceiver 17.15 3 $51.45


ANT-418-CW-QW-ND

418Mhz ¼ wave whip antenna 7.88 3 $23.64


EVAL-418-LT-ND 418Mhz development kit 149.00 1 $149.00

Digi-Key Fairchild Semiconductor

MM74HC164MXCT-ND

14-pin SOIC 74HC-series 8-bit serial to parallel shift register

0.51 3 $1.53

Digi-Key Fairchild Semiconductor

MM74C922N-ND 16-key, 18 pin DIP IC Keypad Encoder 7.75 1 $7.75

Digi-Key Newhaven Display, Intl.

NHD-0224BZ1-FSW-FBW-ND

2 by 24 LCD character display with White LED backlight

15.00 3 $45.00

Mouser Vishay Semiconductor

TSOP-4856 Infrared 56kHz photo detector 0.9975 20 $19.95

Mouser Vishay Semiconductor

TSAL-6100 880nm Infrared 5mm LED 0.2708 15 $4.06

Digi-Key Grayhill Inc. 96BB2-056-F 16-key Telephone Format key pad 13.66 1 $13.66Wal-Mart Store Brand n/a ABS plastic squirt gun 7.50 2 $15.00Digi-Key Fairchild

Semiconductor2N2222A NPN switching transistor 0.335 30 $12.83

All Electronics Store BrandDLM-5

650nm, 4mW Red Laser Diode 6.00 2 $12.00

Digi-Key Memory Protection Devices

BH3DL-ND D-cell battery holder (for 3 cells) 2.18 3 $6.54

EE Parts Room Unknown n/a 10k Potentiometers 1.20 3 $3.60TOTAL $399.64

E-1


Appendix F: FMECA Worksheet

Table F.1 - MicrocontrollerFailure

No.Failure Mode Possible Causes Failure Effects Method of

DetectionCriticality Remarks

1 Pin stuck high or low

Externally driving output pin, software bug, overvoltage, short circuit

That pin becomes useless, system probably breaks

Voltmeter Medium The microcontroller cannot be replaced by the user

2 Chip burns Overvoltage, short circuit

System is unusable

Smell, smoke, hot to touch

Medium

Table F.2 - Vest LED CircuitFailure



1 LED burns out Too much current, heat, physical damage

One LED doesn’t blink

Visual Low Doesn’t break gameplay. Sensor pods are replaceable

2 BJT burns out Too much current, heat, physical damage

Multiple LEDs don’t blink

Visual Low Doesn’t break gameplay. Sensor pods are replaceable

Table F.3 - RF Transceiver CircuitFailure



1 Chip burns Overvoltage, short circuit

No RF communication with that unit

System is unable to communicate

Medium Cannot be replaced by the user

E-2


Table F.4 - LCD systemFailure



1 Broken shift register

Overvoltage, short circuit

LCD fills with one repeating character

Visual Medium Cannot be replaced by the user

2 Broken LCD panel

Overvoltage, short circuit, physical damage

LCD displays strange things or nothing

Visual Low Can be replaced and plugged in by the user

Table F.5 - IR systemFailure



1 IR LED burns out Too much current, heat, physical damage

Unable to shoot Observation Low Breaks gameplay, but can be replaced

2 IR detector breaks Overvoltage, short circuit, physical damage

Unable to detect shots from certain angles

Observation Low Breaks gameplay, but sensor pods can be replaced

3 Lens breaks Physical damage Shots are unfocused

Observation High Lenses are plastic but could still conceivable cause minor harm to the user. This is no worse than the plastic gun being broken.

Table F.6 - Power SupplyFailure



E-3


1 Batteries shorted Loose wires Batteries drained, possible sparking, possible leaking

Observation High Can cause harm to the user, but not easily, as explained previously

E-4