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CHAPTER 1

THE PROBLEM AND ITS BACKGROUND

1.1 INTRODUCTION

Computer has greatly affected the lives of many people due to its numerous uses. It appears

to be an inseparable part of life to many people in these days. Together with the growing use of

computer is the consciousness of the people who use it with its associated peripherals. These

peripherals are the one that gives extra features to the offered functionalities of a computer which

are being enhanced by other sensible individuals. These enhancement or improvements had made

computer more user-friendly for the user. In line with this, the interfacing of the peripherals with the

computer was improved making computer simpler and easier to use. The main idea of this research

is related to some peripherals of a computer which are the flash memory devices specifically the

USB flash drive. This accessible device comprises of two USB ports, one for input and another for

output. Embedded microcontroller is used to allow communication between the two USB flash drives.

The goal of this research is to make transferring data faster and more convenient as it would no

longer entail the use of computer.

1.2 BACKGROUND OF THE STUDY

Most people would like to make backup copies of files to ensure security or any other

reasons. This is where flash memory devices come in. As Cory Janssen mentioned in his article

“Flash Memory”, it is a type of electronic memory which is used for easy and fast information storage

in computers, digital cameras, mobile phones and other electronic gadgets. It is used more like a

hard drive than as RAM and can be electrically removed and reprogrammed. The two main types of

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a flash memory is the NAND and NOR logic gates. This study focuses on the NAND type which is

used in memory cards and USB flash drives.

According to usb.org website, Universal Serial Bus (USB) flash drives are portable memory

drives where you can store data using medium devices such as computers then save it in a several

hosts. Data from USB flash drive can only be read and transferred by a computer or laptop into

another USB flash drive. In today’s world, USB flash drives have been the most commonly used data

storage since they are extremely convenient to have around. The data stored in the USB drive can

last for a long period of time even after power in the computer has been turned off with the drive in

it. In this reason, it has made using USB drive a convenient way for transferring data between a

computer or laptop and a means of providing backup copies for personal needs. In order to transfer

file using a USB flash drive, one need to plug in the device into the USB port of the computer or

laptop, then the operating system will automatically recognize it as a removable drive.

Nowadays, carrying a laptop in order to transfer data from a flash drive to another flash drive

is not practical since people want all devices to be handy. In using USB flash drives, user will not be

able to share files between two USB flash drives if he is away from computer. The necessity of laptop

and computer to transfer a file wastes time and power. Time is wasted on booting in the computer

or laptop just to transfer a certain file from a flash drive to another. When operated, computers

consume a lot of power. Since USB flash drive has been widely used, the proponents used USB as

their interface in transferring data. Aside from that, it is easy to use and very accessible. This study

has been made for data transferring using USB independent from computer. It shows how data is

transferred to the USB mass storage device without the use of a computer. It can be done by making

a system which will serve as an alternative to a computer. This system should do the same roles as

a computer does in data transferring. The prototype will serve as the bridge between two USB flash

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drives that will undergo data transferring. The bridge is a microcontroller based device that will handle

the data transfer and any processes that will be needed. According to www.usbmadesimple.com, all

communications on this bus are initiated by the host. Then microcontroller will enable the USB host

controller to communicate with the USB flash drive. The role of the crystal oscillator is to give the

basic system clock signal. The microcontroller will have a crystal oscillator having its clock set to high

in order for data transferring to be fast. The device supports all USB Flash devices formatted with

FAT32 file system. According to Tim Fisher in his article at pcsupport.about.com, FAT32 stands for

"File Allocation Table," which keeps track of all the files and helps the computer locate them on the

disk.

1.3 OBJECTIVES

The main objective is to construct a prototype that will automatically transfer file from USB

flash drive with another with the use of microcontroller as the bridge. In line with the general objective

of this project, the following specific objectives are:

To develop a device that will perform the data transfer between the USB flash drives.

To design a program that will perform file transfer between the USB flash drives.

To integrate USB host controller to the embedded microcontroller.

To automatically create a default folder in the receiver.

1.4 SIGNIFICANCE OF THE STUDY

In today’s world, Universal Serial Bus (USB) flash drives have been the most commonly used

data storage since they are extremely convenient to have around. Data from USB flash drive can

only be read by a computer or laptop and transfer it from one USB flash drive to another .The problem

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is, if you may not have a laptop or computer, you are unable to transfer important files in a convenient

way. As a solution to this problem, a mini-transfer device can be made to be a medium for the

transmission of data between the USB flash drives.

To the users

These days, not most of us can afford to buy laptops or tablets that has the capability of

transferring data. In this environment, it is risky to bring laptops for thieves are everywhere. So with

the utilization of this tool, no laptop will be needed for the sake of data transfer increasing one’s

safety. So instead of buying laptop in order to have something portable in transferring data, you will

just bring this unique and more portable tool without any hassle.

To the community

The portability and user-friendliness of this tool makes it influential to do data transfer. With

the use of this tool, the owner may optimize power for its consumption will only happen once the

device is being used.

To the environment

This tool is battery operated. AC power supply will not be needed therefore transferring data

can take place anywhere and anytime you want. This will decrease the consumption of power since

you will not use a laptop or computer anymore. In short, it will save time and power in transferring

data from one USB flash drive to another because booting the computer or the use of laptop has

been eliminated.

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To the industry

With some improvements with this device, it can be integrated with other electronic devices

such as pocket wi-fi, usb broadband, and other portable devices. The device can also be

manufactured since it is affordable enough to be bought by the public.

1.5 SCOPE AND LIMITATIONS

The researchers formulated the scope and limitations of this project to identify the

boundaries of the study:

Scope

The device will be able to transfer files from one USB flash drive to another flash drive.

There are two ports available; one USB port for transmitter and another for receiver.

A folder in the receiving flash drive will automatically be created where the files that have

been transferred can be found.

The transfer rate of this device will depend on the host controller to be used.

There will be a multi-colored LED to indicate the condition of the device. The blue light would

indicate that the device is powered on. The LED will turn blinking green when the receiving

flash drive is on process and it will turn stable green if the transferring of data is finished.

Otherwise, when the LED turned red after placing the USB flash drive in the input port and

the other flash drive in the destination port, it means that there is an error either the receiving

flash drive is full or the file is too large.

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Limitations

File selection can only be made by placing the files you want to transfer in the folder of the

input.

High capacity devices such as external hard drive cannot be processed by the device due

to the large amount of memory to read/manage.

Only the files in the dedicated folder of the transmitting drive will be transferred.

The maximum size that the device can transfer is 8 GB.

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CHAPTER 2

THEORETICAL FRAMEWORK / DESIGN CONCEPT

2.1REVIEW OF RELATED STUDIES

2.1.1 Data Duplication Method and System Used Between USB Devices

This study involves data duplication method and system between USB Devices to control

transmission from source USB to target USB without the assistance from a computer. The system

comprises at least Serial Interface Engine, a CPU, and a data buffer unit. The CPU is connected to

the source USB and target USB via Serial Interface Engine (SIE) to control the transmit data from

the source to the target USB Device. The data buffer unit is connected to these serial interface

engines and CPU that is used to provide memory buffer space required during duplication

process.(Kuo & Loo, 2006)

Figure 1 – Aarchitecture Diagram of a Digital Data Duplication System

Source http://www.google.com/patents/US20060206631

This study provided a system that can control one source with many target USB. The source

can be selected from the user interface and the remaining ports are all set as target. The system

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also claimed the system memory to store the firmware that will run the duplication process of the

CPU. The system also claims the user interface has an indication light or an LCD.

Figure 2 - Circular Data Storage Diagram

The following are the duplication method of the study:

- analyzing a file content of digital data in said source USB device and said target USB

devices;

- determining whether any empty storage blocks exist;

- reading digital data of said source USB device and storing the digital data, in order, into said

storage blocks;

- determining, in order, whether said storage blocks are fully loaded With digital data;

- duplicating, in order, digital data in said storage blocks to said target USB devices;

- determining whether duplication of all digital data of said source USB device is finished; and

displaying a duplication-finish message;

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2.1.2 eUSB Duplication System

This study involves digital data copy from master eUSB storage device to target eUSB

storage device that includes a duplicator chassis with multiple standard 5.25 inch optical drive in

length, width and height. For each tray has a multiple eUSB ports that operated electronically by a

digital logic circuit for reading digital data from one eUSB storage device and write the read digital

data to other eUSB storage device. The system includes a controller placed on a top of a chassis

that has the CPU to control the transfer of data. Multiple eUSB decks through which eUSB storage

device can be connected to the eUSB duplication system.(Lee, Yang & Zhang, 2012)

Figure 3 - Perspective View of a eUSB Duplication System

The patent claims described the parts of the system and how they are connected. The system claims

the following:

- A duplicator chassis with multiple sockets for receiving installation of multiple 5.25 inch

devices.

- A controller secured in a tray-shaped frame with overall dimensions of one 5.25 inch device.

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- An electronic circuit mechanically secured within the controller, including a digital logic circuit

for reading digital data from one eUSB storage device and writing the read digital data to

other eUSB storage devices.

- Multiple eUSB decks through which eUSB storage devices can be connected to the eUSB

duplication system.

Figure 4 - Block Diagram of Digital Logical Circuit of the eUSB Duplication System

2.1.3 USB Flash Drive with Selective File Transfer

The invention has a body which includes a non-volatile memory, a USB port and USB host

controller coupled to main memory, USB plug, a program memory containing a control program. The

processor is coupled to the main memory and the two USB port is connected via host controller and

configured to initiate the data transfer between the main memory and one of the port in accordance

with the control program and directionality based on an identity of the one. In one embodiment, the

method includes, employing power source to provide power to the USB host controller, automatically

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identifying a coupling of a USB mass to one of its USB port, automatically initiating of the processor

in data transferring between the non-volatile main memory and in one port.(Hitt & Gaines, 2008)

Figure 5 - High-Level Block Diagram of One Embodiment of a UFD

The device operates wherein a user can automatically transfer files to or from another Flash

Drive without computer; no switches or buttons to be used. The file transfer capability is integral

means that the file transfer capability including the power source is built into the device. The file

transfer is automatic means the file transfer begins when hosted device is plugged into the device,

probably just after the USB connection is established according to the USB protocol. Files may be

transferred only one of two opposite ways, depending on how the two flash drives are plugged into

one another or perhaps based on the user configuration. Only files satisfying one or more criteria are

transferred. The device uses indicator lamp as a to indicate status of file transferring.

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Figure 6 - Flow Diagram of a Method of Operating a UFD

2.1.4 Method Of Duplicating Data To Multiple Random Accessible Storage Devices

The main objective of the invention is to provide a method of duplicating data to multiple

random devices. The steps include the reading of one segment of source data comprised of multiple

segments and detecting the newly connected storage devices, duplicating same segments to all

connected devices. Duplicating the source data stops whenever the random connected device has

stored all the segments of the source data and repeating the process from the start. Same segments

of the source data were written to all connected devices when duplicating. The method will keep

reading the source data in segments and write the same segment of the source data to all unfinished

devices in cycles. Each devices might start duplication from different segments of the source data

since each device is detected non-simultaneously . The duplication will stop once all the data

segments from the source data is complete.

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Figure 7- Functional Block Diagram of a Universal Serial Bus (USB) Flash Drive Duplicator

The method includes the reading and writing the same segment of the source data to all

connected storage devices. The buffer does not need to be divided. Therefore, the buffer will work

more efficiently and at high-speed. (Chang & Kuo, 2011)

2.1.5 Data Transfer Control Device, Electronic Equipment, and Data Transfer Control Method

The data transfer device uses buses (communication system that transfers data between

components inside a computer, or between computers) and Direct Memory Access (DMA). DMA is

a feature of computers that allows certain hardware subsystems within the computer to access

system memory independently of the central processing unit (CPU). The data transfer of this device

is point to point, which is a flash drive to another flash drive. The device is only limited to use

Universal Serial Bus (USB). The device uses a buffer and a buffer management circuit. The buffer is

used for the storage of data and the buffer management circuit manages the writing of data into the

data storage area of the buffer and also does the reading of the data inside the storage of the buffer.

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The data is first stored into the buffer and is then transferred to the desired destination. (Ishida &

Kamihara, 2005)

Figure 8 - Flowchart of Firmware Processing

2.1.6 Data Storage and Transfer Device and Method

According to Pocrass,2009, the device contains a flash memory chip which is for the storage

of data, also connectors are used with this device, such as a memory card connector, a male

connector, and a female connector to be used with the male connector, and serves as the controller

for the transfer of data from one point to another. The device focuses on the connectors which serve

as the medium of the data. Buttons are also available for the control of the data transfer between two

points. In this device, they also use a Liquefied Crystal Display (LCD) which allows the user to see

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the progress of the data that is currently transferring. The device uses the method of transferring

data within a data storage and transfer device. The device provides a data storage and transfer

device having both characteristics of a flash memory chip for storing data, a memory card connector,

a male and female connector configured to mate with each other, inserts a memory card into the

card connector, and allowing the data to pass to or from the memory card from or to at least 1 device.

2.1.7 Apparatus for Multiple Host Access to Storage Medium

The device is created for multiple host access to a storage medium, involving a hot plug/ hot

swap to tie up with the first host, a second hot plug/hot swap interface for incorporating the second

host; storage medium and a control circuit to be able to access and manage the storage medium

from the first host and second host. The device is capable of detecting which interface will access

the storage. The input of the device is limited to a Universal Serial Bus (USB) both the input and the

output. The data transfer of the said device is only point to point, or from one source to one

destination only. After selecting which interface is the source, the device will automatically switch the

function of the other interface to a destination flash drive, so that it will passively receive the data to

be transferred. The capacity of the device is also limited, even though it has its plug-and-play feature

and is easy to manage and carry. USB bridge device is shaped as a long cable, which may be a

hindrance and can cause inconvenience to the user to carry around. This object/device is intended

to eliminate the hindrance of having the inconvenience of carrying a USB bridge, though it only

supports USB flash drives, it can accommodate multiple host access to a storage medium, it has a

detachable cable which is suitable to carry around which is advantageous for the user. (Lu,2005)

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Figure 9 - Connection between a Conventional USB Mini Drive and a USB Host;

Connection between two USB Hosts via a USB bridge device

Figure 10 - Block Diagram of a Apparatus for multiple host access to storage medium

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2.2 REVIEW OF RELATED LITERATURE

2.2.1 USB Communication

Craig Peacock from his blog “USB in a Nutshell” defines USB as a host centric bus.

Therefore a USB communication comes between a host and a device. Universal Serial Bus needs a

USB host, which will act as a master, to communicate to a USB Device/Peripheral like Mass Storage

Devices wherein it will act as a slave. The USB HOST initiates all transaction; bus transfers; establish

enumeration; endpoint communication, and etc.

To access files in a flash drive, Jan Axelson indicated from his book about the considerations

of the system that the host must have. He stated that the system must have USB host-controller

(hardware), mass storage driver firmware (software) and the support for file systems. File systems

on the other hand defines how data are organized in the flash drive. Popular file systems for

embedded systems include FAT16 and FAT32. Then according to him, the embedded system can

then store and read files in off-the-shelf USB storage devices.

In addition, Jan Axelson also stated that embedded hosts must have the following

responsibilities: a) Detect Devices: On power-up, hubs make the host aware of all attached USB

devices. b) Provide Power: The host provides power to all devices on power-up or attachment and

works with the devices to conserve power when possible. c) Manage Traffic on the Bus: The host

manages the flow of data on the bus. d) Handle Error Checking: When transmitting data, the host

adds error-checking bits. When receiving data, the host uses received error-checking bits to detect

errors. And lastly, e) Exchange Data with Peripherals: All of the above tasks support the host’s main

job, which is to exchange data with peripherals.

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Yingbo Hu and Ralph Moore provided a complete part of a Host-Controller. A USB host

requires a USB host controller and USB host software. The latter is layered from the bottom up as

follows: (1) USB host controller driver, (2) USB host stack, and (3) USB class driver. The first layer

controls the USB host controller – i.e. it reads and writes registers in the controller and it transfers

data. The second layer implements the USB protocol and thus controls connected USB devices. The

third layer is device-aware and communicates with and controls the actual device (e.g. disk drive,

HID human interface device, CDC communication device, etc.) One USB host stack can support

multiple class drivers, simultaneously. In an embedded system there usually is only one USB host

controller.

2.2.2 USB Protocol

According to USB 2.0 Specification, up to 127 USB devices can be connected to one USB

host via up to 6 layers of cascaded hubs. For embedded systems, it is very unusual to have more

than one hub. In most cases, one USB device connects directly to one USB host with no hub.

USB hard drives and flash drives are block storage devices. In that, they read, write and

erase in blocks of data and not in streams of data. All USB drives support the logical block addressing

that specifies block of storage capabilities numbered sequentially to read or write to.

Axelson’s research identifies that before reading and writing to files on flash drive, the USB

Host must receive and execute four commands. A) USB hosts learn about attached devices by

sending a series of requests in a process called enumeration. B) The device returns a series of data

structures called descriptors, which describe the device's functions and capabilities. C) A flash drive

sends descriptors that tell the host that the device belongs to USB's mass storage class. D) The host

then knows it can use mass-storage protocols to communicate with the device.

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The Computer Solution LTD’s website said that a typical transaction will consist of a number

of packets - a token indicating the type of data that the Host is sending or requiring, the data and in

some cases an acknowledgement. Each packet is preceded by a sync field and followed by an end

of packet marker.

These transactions are used to provide four basic data transfer mechanisms

Control - used by the Host to send commands or query parameters. Packet lengths are 8

bytes for Low speed, 8-64 for Full and 64 for High Speed devices.

Interrupt - badly named it is in fact a polled message from the Host which has to request

specific data of the device. Used by devices which will be sending small amounts of data

(e.g. mice or keyboards)?

Bulk - used by devices to send or receive data in quantity such as a printer. Variable length

blocks of data are sent or requested by the Host (max length is 64-byte- full speed, 512 -

high speed), are verified with a CRC and their receipt is acknowledged. This mechanism is

not used by time critical peripherals as it takes whatever bandwidth is left by the other

mechanisms.

Isochronous - used for devices that stream data in real time without any error recovery such

as audio channels. For them losing some data occasionally is better than the glitch resulting

from a re-transmit. Packet sizes can be up to 1024 bytes.

Then according to Kim Otten of Microchip Technology Inc, from the four transfer types

supported by USB, the most suitable for large data transfer is Bulk. The bulk utilizes the bandwidth

allocation efficiently, in that it depends on the amount of other traffic that is on the bus. This means,

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the bulk transfer always utilize the remaining bandwidth in a frame after Control, Interrupt and

Isochronous transfers are complete.

2.2.3 BUS Speed and Throughput

The USB 2.0 specification defines three bus speeds: high speed at 480 megabits/sec., full

speed at 12 megabits/sec., and low speed at 1.5 megabits/sec. A USB mass storage device must

support full speed, high speed, or both.

These speeds don’t mean that this will be the transfer rate of data. It’s a big no, because the

bandwidth allocates all the four transfer types. Among the four transfer types, isochronous and

interrupt devices requests has the highest priority being allocated for about 90 percent of the frame.

Control and Bulk will then guaranteed at least 10 percent with control taking priority which has

requests the device’s descriptors, which are data structures that contain information about a device’s

capabilities and requirements.

According to Jan Axelson, all bus traffic is to or from device endpoints. An endpoint serves

as a buffer for received data or data waiting to transmit. Typically an endpoint is a block of data

memory or a register in the device controller.

According to a case study made by the researchers of CoActionOS Website

(http://www.coactionos.com), they illustrated that 32-bit microcontroller architectures can boost

performance as compared to 8-bit and 16-bit microcontrollers without a cost increase. The case

study offered a simple comparison between several microcontroller architectures (8-bit, 16-bit, and

32-bit) of the same package (QFP100) and roughly the same price. The following table shows the

comparison which were simplified in order to give a rough idea of the relative value of each

microcontroller.

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Table 1 – Comparison between 8, 16, and 32 bit microcontrollers

2.2.4 Choices of Implementation

Chips with built-in support for host functions:

Vinculum II

Vinculum-II (VCN2) is a programmable USB Host 2.0 / Slave controllers. It features

a powerful 16-bit MCU core, with embedded 256KB Flash, 16KB RAM memory and supports

flexible interfaces including UART, SPI, FIFO and PWM. The complete USB protocol data

processing is handled entirely by hardware resources within the device freeing up

processing resources for user developed applications. It uses ‘C’ based development

environment to enable user firmware development.

(http://www.ftdichip.com/Products/ICs/VNC2.htm)

USBwiz

According to Jan Alexon, A Mass-Storage Host Module, another approach to

designing an embedded host is through USBWiz of GHI Electronics. It is a Philips LPC2138

ARMcessor which supports FAT file systems and several USB device classes and mass

storage. It enables just any microcontroller to access USB Drives and flash-memory cards.

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Microcontrollers can communicate with the USBWiz using asynchronous serial interface,

SPI or an IC bus. It responds to commands sent in text mode, ANSI text or in framed mode,

and binary values.

Microcontrollers with USB host ports:

Cypress Semiconductor

Cypress’s host controllers have the versatility of USB to a design. It has a single

and dual role host or peripheral controllers. It allows any design of USB ports to have both

device and host capabilities. Its high performance USB host controllers are used in

embedded applications such as PDAs, Set-top Boxes, Personal Media Players and

Automotive Infotainment. (http://www.cypress.com/?id=186&source=header)

Microchip Technology PIC24 and PIC32 series

Both PIC24 and PIC32 has the USB On-The-Go (OTG) features which allow

embedded devices to become hosts to other USB devices without the use of PC. It allows a

design to be used as either an embedded host or peripheral. USB can now be implemented

in a 16-bit system. It has USB hosting options, using a FAT file system library and process

for developing a custom class driver and an application that acts as a host to a simple USB

device. (Microchip Technology Inc.)

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2.3 THEORETICAL FRAMEWORK

The input block contains the involvement of hardware used. These include careful

researches with regards to the ideal type of microcontroller to be used and the appropriate USB Host

Controller. The process block contains the methods used in the implementation of a microcontroller

based USB-to-USB bridge. It involves the integration of USB host controller to the embedded

microcontroller. Output block is implementation of the microcontroller based USB-to-USB Bridge for

data transfer in accordance with the design requirements.

Paradigm 1 – Conceptual Framework

INPUT

•USB Host Controller

•PIC Microcontroller

•Programming Methods

• LED Indicator and button

•Battery

• Flashdrives

PROCESS

•Program the USB Host controller and the Microcontroller

• Synchronize all the hardware

•Access and enable communication between two flash memories

•Circuit Design

OUTPUT

• Implementation of Microcontroller based USB-to-USB Bridge For Data Transfer

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2.4 DESIGN CONCEPT

Figure 11 – The Design Concept of Microcontroller-based USB-to-USB Bridge For Data

Transfer

To begin with, the selection of USB Host Controller must be done. USB Host Controller has

the capability to recognize the device firmware loaded in it. It handles the communication between

two ports that configured as a host and slave. A next criterion is the availability of two USB Port in

the host controller so that it minimizes the use of additional hardware. And most of all, host controller

must have file system support (FAT32) to read the files on a USB device.

The USB Host Controller will do the job as a Host which handles all USB protocols and

communications between USB Flash Drives. It also contains Operating system to run the FAT32 File

System and device drivers to interact with the devices. It has all the responsibilities like initiating

transfers, endpoint communication, pipe establishments, packet transferring and receiving, etc. This

is also the bridge for microcontroller and the USB device.

Microcontroller is the heart of the system; it has all the instructions to interface the LED and

the USB Host Controller. Microcontroller must have enough memory to save all the functions. It must

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have a TXD and RXD pins so that embedded host controller can instruct what to do. And it must

have enough I/O ports to interface all the hardware to be connected from it. Microcontroller has the

ability to consume less power to run many instructions.

Aside from that, the microcontroller must be programmed necessary instructions. The device

must power up the two flash drives via vbus and ground. Every flash drive requires 200mA each. A

5V power supply is required to provide 200mA at USB Ports, 25mA at USB Host Controller and

25mA at the microcontroller. The clock is also important to provide higher baud rate which makes

the performance of the system improve. USB Host controller and microcontroller have RTS/CTS

Handshake simulations to allow communication via UART.

The design also includes multi-colored LED consisting of green, red, and blue color. It will

serve as indicators and are powered at the pins of the microcontroller. This will indicate the transfer

of file and successful access of the file system.

The proponents will use the C compiler for the microcontroller programming and Simulation

and development tools. The said devices define roles for the completion of this design.

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CHAPTER 3

OPERATIONAL FRAMEWORK

This chapter is divided into four (4) main parts. This includes the Project Design, Project

Development, Testing Procedure, and Implementation. The Project Design comprises Chassis

Design, System Design, and Communication Design. Next is the Project Development involves the

conceptualization of the prototype and planning its implementation. Next is the Testing Procedure

which evaluates the capacity of the device and its functionality. Another is the Implementation

wherein the execution of the device is discussed. Constraint Analysis and Technical Standards were

also added in this chapter.

3.1 PROJECT/RESEARCH DESIGN

This part is divided into three (3). First is the Chassis

Design. As the name implies, it includes the layout of the

prototype with its respective dimensions and components. The

design of the chassis includes the design of the Input controls for

the device. The chassis also provides the Light Indicators before,

during and after the data transferring. On the second part, the

System Design involves the flow of the program and the

programming that is used. This part has an objective to integrate

the all the required embedded systems hardware including the

controls and indicators. The third part involves the communication

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for the Mass Storage Devices. USB communication strongly suggests the use of a host which

composed of a USB Host Driver (Software) and USB Host Controller (Hardware).

3.1.1 CHASSIS DESIGN

The aim of this research is for the device to be handy, small and lightweight. Portability will

be a necessity for this device. Its goal is for it to make the user more convenient during times when

he has urgent tasks to fulfil. Considering this matter, the dimension is 5 by 5 cm. Plastic casing will

be used to consider the weight factor. Aside from that, plastic is cheaper compared to that of

aluminium or glasses making the researcher spend more on the internals. Furthermore, plastic is

durable and easy to mass produce.

The chassis consists of two (2) USB ports, one is for the source and the other one is the

target device. Once the transmitting and receiving devices are placed in the USB ports, the files in

the default folder will automatically be transferred. The LED indicator will indicate the transfer is

happening (green blinking), transfer completed (steady green) or if communication is not allowed

(steady red).

Figure 13 - The chassis design

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3.1.2 SYSTEM DESIGN

The system design includes the system architecture, flowchart, and algorithm. It simply

discusses the processes that the system undergoes and how it is implemented.

3.1.2.1 System Architecture

It will be helpful to the designer to study the system architecture that will serve as a guide

for its processes. The figure shows the hardware to be used. The system architecture composed of

Embedded Microcontroller which is the main controlling circuit of the system. It will use its general

purpose input/out pins for the controls and indicators. UART, SPI, FIFO or 𝐼2𝐶 are going to be used

here as an interface communication between microcontrollers which will be use here for USB Host

Controller. The USB Host Controller has the two ports for USB interface which will allow

communication from Source Device (Flash Drive 1) to microcontroller (RX) and microcontroller (TX)

to Target Device (Flash Drive 2). The overall system mainly uses a power supply that will enable the

system to function properly. The power supply here is a rechargeable battery that must be small

enough to fit into to chassis and can withdraw an enough power for each of every device, especially

the Mass Storage Devices.

The summaries of components are as follows:

Embedded Microcontroller (32-bit Core)_

USB Host Controller (Hardware)

Power Supply (Rechargeable Battery)

Controls and Indicators (LED Lights and Control Buttons)

Mass Storage Devices (Source and Target USB Drive i.e. Flash Drives)

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Controls and

Indicators

Power Supply

USB Host

Controller V V

V V

Figure 14- The system’s architecture

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START

Insert flash drive to be copied

to the source USB port

Insert receiving flash drive to

the destination port

Green

LED

blinking ?

3.1.2.2 System Flowchart

Figure 15- The system flowchart

Yes

Yes

No

No

File transfer complete

Transferring of file

END

Receiving flash drive is full or

the file is too large

Green

LED

steady?

LED turns Red

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3.1.2.3 Algorithm:

1. Start

2. Insert flash drive to be copied to the source USB port

3. Insert the receiving flash drive to the destination port

4. Green LED is blinking while transferring files from the source flash drive to the destination

flash drive. LED turns Red if the transfer is not allowed i.e. error, destination storage is full.

5. LED stops blinking and the LED turns steady green when transferring of data is complete.

6. Stop.

3.1.3 COMMUNICATION DESIGN

In this part of the study involves the communication between embedded microcontrollers

and the USB Host Controller. Wherein the microcontroller enables transmit and receive of the data

from the USB Host Controller. The USB Host Controller on the other hand handles the protocol

between the two USB mass storage devices. The said two embedded devices were both

microcontrollers so that the communication between the microcontrollers will be needed in this part.

According to Jan Axelson, communications between microcontrollers can be

establish by using its serial communication ports like UART, USART, FIFO, SPI or the I2C. According

to Microchip Technology Inc, Serial Peripheral Interface is a synchronous serial bus and operates in

full duplex mode. It is a synchronous protocol that allows a master device to initiate communication

with a slave device . It allows serial communication between two or more devices at a high speed.

Using SPI, the two microcontrollers can communicate in master/slave mode. PIC32 microcontroller

operates in master mode and the Vinculum II USB host controller acts as the slave.

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3.2 PROJECT DEVELOPMENT

For the implementation of the USB-to-USB bridge for data transfer, several stages are to

consider. The project development includes the Selection of USB Host Controller wherein the

researchers made several studied the most suitable host controller to use. Next is the Selection of

PIC Microcontroller which involves the comparison with other microcontroller choosing the one that

offers that best data transfer rate. Another is the Design of Software Program which involves several

codes to be used for the project. The fourth is interfacing the Hardware Module specifically the PIC

microcontroller to the USB Host Controller. That is to be followed by the test and evaluation of the

project. Aside from that, to ensure the functionality of the project and in case of any problem,

debugging and troubleshooting will be done. Last part is designing the chassis.

Figure 16- Phases of the Project Development

• Selection of USB Host Controller

• Selection of PIC Microcontroller

• Design of Software Program

• Interface the Hardware Module

• Test and Evaluation

• Debug and Troubleshoot

• Design of Chassis

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3.2.1 Selection of USB Host Controller

There are few host controller modules in the internet but the criterion must have two USB

ports available. The host controller recognizes the input peripheral as host or slave according to

firmware loaded in it. The sub module physically interfaces with the USB flash drives and is

responsible for converting raw data and information to their proper NRZI encoding as specified by

the USB technical specifications. It handles all types of transfer between source destinations. The

researchers have selected a USB Host controller which has two independent USB 2.0 low

speed/high speed USB Host ports. Individual ports can be configured as host or slave.

FTDI’s 2nd generation of USB Host/ Slave controllers, Vinculum II (VNC2), was selected as

the USB Host Controller. It features dual USB 2.0 Host controller in a single IC with a powerful 16-

bit MCU core. It has embedded 256KB Flash and 16KB RAM memory. VNC2 can handle complete

USB protocol data processing with a capability to encapsulate USB device classes by handling the

USB Host Interface and data transfer functions . It has built-in Serial Peripheral Interfaces which is

used to interface with the PIC microcontroller. It is fully programmable and supports ‘C’ based

programming for firmware development. VNC2 provides a cost effective solution for USB host

applications.

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Figure 17 - Functional Block Diagram of Vinculum II

Source: http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_Vinculum-II.pdf

Figure shows the functional block diagram of VNC2 provided by the FTDI. Starting with the

Embedded CPU, It is a processor core based on FTDI’s 16-bit MCU architecture. An EMCU

architecture with a separate code and data space. The flash programming module is responsible for

all the operations needed to program the flash. It handles the firmware upgrades which accessed

through debugger interface, USB cable or Flash interface. The flash module has 256k bytes of

Page | 35

embedded flash (E-Flash) memory. Input/ Output Multiplexer Module is where the peripheral

interfaces were connected. It allows the user to programmer to select which peripherals are

connected to the I/O pins. The peripheral DMA Modules transfer data to and from an I/O device. It

transmits or receives data from memory to an I/O address space. It can also copy data from memory

to another location. DMA is automatically controlled by the CPU. VNC2 has two USB transceivers in

which the physical USB interface is connected. It supports USB 1.1 and USB 2.0 standards with low-

speed and full-speed USB data rates. Each output driver +3.3V level control signaling. The USB

Host/ Device Controllers handles the parallel-to-serial and serial-to-parallel conversion of the USB

physical layer. The clock is provided by a 12MHz Oscillator cell. It generates a 12 MHz reference

clock input to the Clock Multiplier PLL from an external 12 MHz crystal.

3.2.2 Selection of PIC Microcontroller

According to a case study made by the researchers of CoActionOS Website

(http://www.coactionos.com), they illustrated that 32-bit microcontroller architectures can boost

performance as compared to 8-bit and 16-bit microcontrollers without a cost increase. The case

study offered a simple comparison between several microcontroller architectures (8-bit, 16-bit, and

32-bit) of the same package (QFP100) and roughly the same price. The following table shows the

comparison which were simplified in order to give a rough idea of the relative value of each

microcontroller.

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Table 1 – Comparison between 8, 16, and 32 bit microcontrollers

The researchers choose PIC32 because it is suitable for implementation of fast processing

speeds. It also depends on the program that will be installed on the microcontroller whether what

type of instruction it will follow. It also has a built in oscillator in which we can manipulate the speed

of the microcontroller. It is perfect for our objective to be able to create a device that will be small

and suitable for travel and daily use because the microcontroller itself is small and easy to handle.

Another reason is that the microcontroller is inexpensive, and has a wide range of interface which

we can use to program the device. The device also has the highest execution speed 80 MIPS and

the largest flash memory. It also has full speed Host/Dual Role and OTG USB capabilities. The USB

On-The-Go (OTG) feature allows embedded devices to become hosts to other USB devices without

the use of PC. It can either be an embedded host or peripheral for it has USB hosting options. USB

can now be implemented in a 16-bit system, using a FAT file system library and process for

developing a custom class driver and an application that acts as a host to a simple USB device.

(Microchip Technology Inc.)

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3.2.3 Design of Software Program

The development of the project involves the programming of the microcontrollers. A USB

device stack is the software necessary to drive the USB device peripheral hardware on a

microcontroller (MCU) or other device (Alan Ott, Signal 11 Software). Typically, USB peripheral

hardware only supports the transaction level and below of the USB protocol. Enumeration and

transfers are left to the firmware or software to implement.

USB device hardware initialization

USB interrupt handling

Management of the serial interface engine SIE

Management of endpoints

Fragmentation and reassembly of control transfers

Handling and sending standard setup requests

Enumeration

Microchips Application Note “USB Embedded Host Stack Programmer’s Guide” by Bud

Caldwell of the Microchip Technology Inc describes how to use the USB embedded host stack

firmware when a sample application is not available to perform the desired task.

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3.2.3.1 USB Embedded Host Firmware Architecture

Figure 18 – USB Embedded Host Firmware Stack

1. Application Layer

The application layer is the firmware necessary to implement the deviceís desired behavior.

It is customer designed and implemented code, although it may be based on Microchip supplied

sample code. The application layer communicates with a USB device through one or more USB

client drivers, and uses any other firmware in the system, as necessary.

2. USB Client Driver

Each USB peripheral device implements a particular function (printer, mouse, mass storage

device, etc.).Some devices may have multiple functions. A USB client driver enables the embedded

host’s application firmware to control a single function of a USB peripheral device that is connected

to the host. Multi-function devices will usually be controlled by multiple client drivers. The client driver

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should model the function in an abstract way, so that the host application does not need to

comprehend the details of how the device works.

3. USB Host Layer

The host layer provides an abstraction of the USB, supplying the following services:

Performs device identification

Performs device enumeration

Manages client drivers

Provides a simple interface to communicate with a USB peripheral device

When first connected to the bus, the host layer will read the descriptors (data structures defined

by the USB 2.0 and its associated supplements) from the device to determine what type of device it

is and what function(s) it supports. Then, it will check the TPL to see if the device can be supported.

If it can be, the host layer will initialize the appropriate client driver (or drivers).

3.2.3.2 Implementing an Embedded Host’s Firmware

This section describes the steps necessary to design and implement the firmware for an

embedded USB host using the Microchip framework.

Implementing the Main Application

Using MPLAB IDE, create a new application for the supported microcontroller. (Refer to the

MPLAB IDE online help for instructions on how to create a project.) Implement and test any

application-specific non-USB functionality desired.

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To support the USB FW stack, the applicationís main function must call USBInitialize, once

before any other USB activity takes place. After USBInitialize has been called, the application must

call USBTasks in its main loop.

Figure 19 – An Example of the Main Application Routine

Figure 20 – An Example of the Application Event Handler

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The table 2 shows by Kim Otten of Microchip Technology Inc. used in data logger application

to access the Mass Storage Client Driver. For table 3, it shows the functions to interface with the

hardware.

Table 2- Files used for data logger application

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Table 3- File System Interface Functions

3.2.3.3 Performing a Transfer

Communication with a Peripheral is initiated by two functions (AN1142: USB Mass Storage Class on

an Embedded Host):

The commandBlock is a block of up to 16 bytes that tells the Peripheral which operation to

perform. When the SCSI media interface layer is used, this block contains the SCSI command to

perform the requested operation.

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A return code of USB_SUCCESS (0x00) indicates that the operation was started

successfully. After initiating communication, take care that USBHostTasks() and

USBHostMSDTasks() are performed while waiting for the operation to complete. The status of the

operation can be determined by calling the function:

If the function returns FALSE, the transfer is not complete, and the returned error code and

byte count are not valid. If the function returns TRUE, the returned error code indicates the status of

the operation, and the returned byte count indicates that how many bytes were transferred. A transfer

of data from the Host to the Mass Storage Peripheral appears as Example 1.

3.2.4 Interface the Hardware Module

Serial Peripheral Interface (SPI) was used to interface the PIC microcontroller to the USB

Host Controller. It is a synchronous protocol where in a master device initiates the communication

with a slave device. SPI is built into both PIC32 and Vincullum II MCU by a hardware module. It

allows serial communication between two or more devices at a high speed. The hardware modules

we’re interfaced wherein the PIC32 microcontroller operates in master mode and the Vncullum II

USB host controller acts as the slave.

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Figure 21 –SPI Communication

Souces: http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_Vinculum-II.pdf- August 26, 2013

Communication between microcontrollers as presented by the block diagram involves the

use of SPI ports. It has four wire ports and specifies the logic signals namely: SCLK which is the

serial clock, MOSI (master output, slave input), MISO (master input, slave output) and SS (slave

select). First, the master (PIC32) configures the clock (SCLK) with frequency equal or less than to

the maximum frequency of the slave supports. VNC2 operating in slave mode has an SPI maximum

clock of 24MHz. The clock signal is only provided by the master for synchronization. It controls the

transferring of data, when it will change and valid to be read. The SS signal will control when a device

is accessed. It indicates that the PIC32 wishes to start a data exchange with the VNC2. The SS

signal is low when SPI is active and the slave will listen for clock and data signal. Since SPI is

synchronous, it has a clock pulse along with the data. Data is always exchanged between the

devices. Operating in full duplex mode, MOSI and MISO pins will be used here as the way of data

Page | 45

exchange between them. Each device has two data lines, one for input from slave going to master

(MISO) and one for output from master going to slave (MOSI).

3.2.4.5 Testing Procedure and Evaluation

The hardware to be use in this device must be properly selected to meet the requirements

of the device and function properly. Selection of USB Host Controller will be the stepping stone for

this project. This means it will handle the provision of USB communication protocol for the USB

Slaves. Series of test and evaluation will be implemented to assure the functionality of the device.

On the first test, the file transferred from the source to destination should have the same content.

Another evaluation is the accuracy of the file. The desired output must be the same from the source

and it must not be corrupted. Speed of the file transferring is also assessed; the desired throughput

must match with the device. There will be three sets of files to be transfer: Small, Medium and Large

Files. The average speed for these sets will be recorded respectively. The effective throughput is

from 32 to 280 Mbps, specification of USB 2.0 Hi-Speed.

3.2.4.6 Implementation

USB Host Controller: There are many host controller modules in the internet but the criterion

must have two USB ports available. The host controller recognizes the input peripheral as host or

slave according to firmware loaded in it. The sub module physically interfaces with the USB flash

drives and is responsible for converting raw data and information to their proper NRZI encoding as

specified by the USB technical specifications. It handles all types of transfer between source

destinations. We have USB Host controller which has two independent USB 2.0 low speed/high

speed USB Host ports. Individual ports can be configured as host or slave.

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Embedded Microcontroller: It is an open source design that has been tried by many users

so the debugging of program is not a great problem. This makes it easy to find help in troubleshooting

and debugging projects. It has a very convenient power management that can be supplied voltage

as low as 5V to run the microcontroller. It is an easy to find microcontroller brain which has choices

of clock speed that is fast enough to run most of the applications. It has 32 KB of flash memory for

storing the code and the number of I/O pins. Theses pins allow us to connect external hardware to

the PIC which can be connected the USB Host Controller and LED.

Experiments and evaluation of microcontroller will be the main tasks of the proponents.

Microcontrollers will be selected according to the size, cost and implementation. The two flash drives

must have a default folder wherein the files to be transferred are located at the said folder. The

design of the device must meet the small size and portability. There will be two programs for this

device, one for the USB host controller and one for the PIC microcontroller. For production design,

these microcontrollers must be pre-programmed first prior to the insertion to the pc board. The

proponents will use USB Development Board kits as an evaluation and practice of the

microcontrollers.

3.5 Task to be Performed / Time Schedule

A Gantt Chart was used to list the task to be performed with the target date to finish each

task. The first semester period was done in planning the prototype and the other semester is the

development of the device.

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Figure 22 – Gantt Chart

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3.5 CONSTRAINTS ANALYSIS

3.5.1 Hardware Constraints

One of the constraints in hardware design includes the addition of hardware controllers that would

cause the device chassis to become possibly big. Since Vincullum II involves two USB port needed for the

bridge, the proponents had decided to use it. Other host controller has only one USB port which would require

using another host controller which is not ideal since the chassis would become bigger.

3.5.2 Financial Constraints

In making the design project, finance is a great factor. LCD display for file selection has been

considered but due to its expense, the researchers decided to not use one anymore. Since the only function

of the prototype is to transfer file, it would be impractical to spend a lot of money for a simple function. One

of the researcher’s goals is to have device price lower than that of a laptop or anything that can transfer file.

3.5.3 Physical Dimension and Weight

The bridge has a limit on its dimension. The researchers had set a maximum dimensions for width,

length and height of the prototype. That is 5cm by 5cm by 3cm. The prototype must also be lightweight.

3.6 TRADE-OFFS

Based on the constraints considered above, several decision on the criteria are made. The

importance of each criterion are scaled from 0 to 5 having 5 as the highest importance. The following are

listed and ranked below.

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Decision Criteria Criterion’s

Importance

Disadvantage Design Consideration satisfy the criterion

Hardware 5 One microcontroller cannot support two USB hosts.

Integration of PIC32 and Vincullum II which has two USB host capability.

Cost 4 Availability of the hardware is only available outside the country.

LCD for file selection are expensive. It would make the expenses for the product to cost much.

Since PIC32 have met the requirements needed to implement a faster rate of data transfer and is compatible with Vincullum II, it has been chosen.

The transmitting USB device must place the files he want to transfer in a default folder. Only the files in the dedicated folder of the transmitting device will be transferred. For the receiving device, it will automatically create a default folder wherein all files transferred are place.

Physical Dimension and

Weight

4 Since two controller are to be used, the size of the bridge became bigger.

The two controllers were integrated in one small PCB. Plastic casing was used since it is lightweight.

Table 4 – USB-to-USB Bridge Design Criterion

3.7 TECHNICAL STANDARDS

3.7.1 Introducing the Universal Serial Bus

Every personal computer or laptop has USB ports that can connect to mouse, scanners,

printers’ keyboards, drives, etc. USB was designed as an interface to allow communication among

the many types of devices or peripherals. This interface has a great benefit for the users and

developers. This includes ease of use, low-cost reliable, multiple speeds, low power consumption,

versatile and OS support.

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With the USB 2.0 specification at 650 pages, USB as its name would suggest is a serial bus.

It uses 4 shielded wires of which two are power (+5v & GND). The remaining two are twisted pair

differential data signals. From the Figure 1, Pins are numbered from 1 to 4 which identify the use of

each of the pins. Pin 1 and 4 are VBUS and ground respectively. The remaining two (Pin 3 and 4)

are for differential data signals which is the D- and D+ respectively. It uses a NRZI (Non Return to

Zero Invert) encoding scheme to send data with a sync field to synchronize the host and receiver

clocks.

Figure 23 – Types of USB Connector

USB supports plug’n’play and hot pluggable with dynamically loadable and unloadable

drivers. The user simply plugs the device into the bus. The host will detect this addition, interrogate

the newly inserted device and load the appropriate driver all in the time it takes the hourglass to blink

on your screen provided a driver is installed for your device. The end user needs not worry about

terminations, terms such as IRQs and port addresses, or rebooting the computer. Once the user is

finished, they can simply lug the cable out; the host will detect its absence and automatically unload

the driver. (Jan Axelsons Lakeview Research)

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Figure 24-Host and Peripherals diagram

All peripheral can be connected through a direct USB port (P. Polishuk, "1394 Newletter,"

vol. 2, 1998). Wired USB technologies can be categorized into following main categories:

A. USB 1.0 - USB 1.0 has a full speed of 12 Mbits/sec and a low speed of 1.5 Mbits/sec.

B. USB 2.0 - USB 2.0 is almost 40 times faster than USB1.0. It can provide full speed of up to

480 Mbits/sec.

C. USB 3.0 - It is targeted to be 10 times fast than USB 2.0. However it is under development

process.

USB communications require a host computer. According to the USB specification, up to

127 peripheral devices can be connected to the host. It is made up of several layers of protocols.

Each USB transaction consists of a 1) Token Packet (Header defining what it expects to follow), an

2) Optional Data Packet, (Containing the payload) and a 3) Status Packet (Used to acknowledge

transactions and to provide a means of error correction). The communication of host (master) and

device (slave) was through what we call a pipe from its endpoint buffers. Pipe was defined as a

logical connection between the host and endpoint(s) and the endpoint can be described as sources

or sinks of data. The Figure 2 fully describes the endpoint and pipe.

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Figure 25- Data transfer between host and device block diagram

Data transferred between the host and the device is categorized into three categories

including common data, command block wrappers (CBW) and command status Wrappers (CSW).

Common data is transferred through bulk end point buffer and data belonging to CBS and CSW is

transferred through interrupt point buffer. A microprocessor controls the operations storage module,

the control endpoint buffer, the bulk endpoint buffer and the interrupt endpoint buffer. (Muhammad

Usman Rashid Bulletin of Electrical Engineering and Informatics, Vol.1, No.4, December 2012, pp.

263~278).

The Universal Serial Bus specification defines four transfer/endpoint types,

Control Transfers

Interrupt Transfers

Isochronous Transfers

Bulk Transfers

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All USB devices have a hierarchy of descriptors which describe to the host information such as

what the device is, who makes it, what version of USB it supports, how many ways it can be

configured, the number of endpoints and their types etc.

The more common USB descriptors are

Device Descriptors

Configuration Descriptors

Interface Descriptors

Endpoint Descriptors

String Descriptors

3.7.2 Accessing Flash Drives

Mass-storage devices typically store information in files. A file system defines how the files

are organized in the storage media.

WHEN TO USE A STORAGE DEVICE

If the device has a Universal Serial Bus (USB) interface, any PC or other USB host can

access the storage media. Another option for some systems is to add USB host-controller hardware

and mass-storage firmware. The embedded system can then store and read files in off-the-shelf USB

storage devices.

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CONSIDERATIONS

Mass-storage firmware is complex. If the device firmware needs to create, read, or write to

files and directories on its own (not via the USB interface), the firmware must also support a

file system.

USB mass-storage devices transfer data using bulk transfers.

A storage device should have one mass-storage master at a time. The master, or mass-

storage host, is the computer that reads and writes to the storage media. Devices that

support two masters can have a manual or electronic switch to enable one master at a time,

or a device can use firmware protocols to inform the host when the media’s contents have

changed.

REQUIREMENTS

Devices

Devices that create, read, or write to files and directories on their own (not via a USB host)

must implement a file system. A file is a named collection of data. A directory structure provides an

index to the files. Popular file systems for embedded systems include FAT16 and FAT32. An

embedded system that accesses flash-memory cards or hard drives must have a microcontroller or

other CPU or intelligent hardware to manage communications with the cards or drives. USB hard

drives and flash drives are block storage devices.

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Embedded Hosts

A microcontroller or other CPU or intelligent hardware to manage the embedded system’s

operation. A USB host controller, which can be embedded in a microcontroller chip or on a separate

chip that interfaces to the CPU, microcontroller, or other intelligent hardware. The hardware or

firmware in an embedded USB mass-storage host must provide the following functions:

1. Issue USB requests and initiate other events on the bus to identify attached devices and

manage traffic and power on the bus.

2. Issue USB mass-storage requests that ask for status information or specify actions for the

device to perform.

3. Issue SCSI commands in USB transfers. The commands read and write blocks of data in

the storage media, request status information, and control the device operation.

4. Support a file system to access files in the media.

SELECTING MEDIA TYPES

For many devices, flash memory is a good choice for storage media. Flash-memory cards are

physically small, can store moderate amounts of data, and manage the low-level protocols for

accessing the memory. Some cards require only a few port pins to access. Flash memory consumes

less power than other media types.

Drive Mechanism

Flash memory resides in chips. Accessing flash memory requires no moving parts.

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Addressing Methods

*All USB drives and other drives of recent vintage support logical block addressing

(LBA).With LBA, blocks of storage capability are numbered sequentially beginning at zero. All blocks

have the same size, again typically 512 bytes. The logical block address is often referred to as a

sector address because the block size equals the capacity of a sector in a hard drive.

*To access the media, software specifies the logical block address to read or write to. For flash

drives, the drive’s controller translates each LBA to a block, page, and column in the memory array.

Reading and Writing Considerations

1. Write Protection: The storage media drive mechanism, circuits, or a manual switch can

permit or forbid writing to the media. Higher-level software in the mass-storage master can

also control access to data on a storage device.

2. Erasing: The flash memory used in storage devices must be read and written in pages and

erased in blocks.

3. Security: Some media types have built-in copy-protection capabilities.

Removable Media and Devices

*Removable Media: In a drive with removable media, users can easily insert and remove

media in the drive. CD/DVD drives and memory-card reader has removable media while Hard drives

and flash drives have non-removable media because you can’t easily remove the hard disk from its

drive or the flash memory from its circuit board.

*If a device or card is removed while the host is writing to the media, the device and host

should detect the removal and handle it as gracefully as possible.

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MASS STORAGE REQUIREMENTS

An interface descriptor with the class code = 08h (mass storage).

A bulk IN endpoint and a bulk OUT endpoint that belong to the mass-storage interface.

A serial number stored in a string descriptor.

Storage media.

The ability to access the storage media’s contents using logical block addressing.

Support for the USB mass-storage class’s protocol for receiving and responding to

commands required for the mass-storage interface’s subclass and peripheral device type.

(Source: Axelson, Jan. USB Mass Storage: Designing and Programming Devices and Embedded

Host, 2006 Lakeview Research LLC Madison, WI, Independent Publishers Group)

3.8 COST ANALYSIS

The project is estimated cost shown in Table 4. The cost may vary through the development

of the design. The materials needed to create the design project are:

Materials Cost

USB Host Controller (Vincullum II) P 300.00

PIC Microcontroller (PIC 32) P 300.00

Rechargeable Battery P 200.00

Casing P 200.00

Multi-colored LED P 10.00

1 Button P5.00

TOTAL P1015.00

Table 4. Materials and Estimated Cost

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NON-ELECTRONIC SOURCE

1. Axelson, J. (2002 January). No Power Supply Required: Powering USB Devices. Circuit Cellar, pp. 26-30.

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3. Bachiochi, J. (2008, October). Get Started with PIC USB Connectivity. Circuit Cellar, pp. 24-33.

4. Cantrell, T. (2001, September). Get Bluetruth. Circuit Cellar, pp. 74-78.

5. Eady, F. (2001 October). The Basics of USB. Circuit Cellar, pp. 48-53.

6. Eady, F. (2010 August). Taking USB Downstream. Nuts and Volts, pp. 54-59.

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8. Hyde, J. (2007, July). Flash Drive Connection. Circuit Cellar, pp. 59-67.

9. Lemieux, J. (2010 September). Making the SD-USB Connection. Nuts and Volts, pp. 12.

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13. Axelson, J. (2009). USB Complete Developer’s Guide 4th Edition. Misconsin, United states of America.Lakeview Research LLC.