smart product design

3/8/2010 ME 8243 LECTURE NOTES 1

SMART PRODUCT DESIGN

LECTURE NOTES


PIC CHIP MICROCONTROLLER OVERVIEW


Resources

• http://microchip.com/• http://ww1.microchip.com/downloads/en/DeviceDoc/39630C.pdf


PICmicro ARCHITECTURE

Ref: “Architecture - PICmicro Mid-Range MCU Family “


Harvard Architecture


PICF88 ARCHITECTURE


PICF88 MEMORY ORGANIZATION


PICF88 STATUS REGISTER


CPU AND REAL-TIME SAMPLING CLOCKS


System Clocks


Instruction Cycle

• 1 instruction cycle = 4 oscillator cycles• If 4 MHz oscillator, 1 instruction per

microsecond


'16F88 Clock Choices

• 8 MHz, 4 MHz, 2 MHz, 1 MHz, 500 KHz, 250 KHz, 125 KHz

Challenge Question:Why not always go at 8 MHz?


Table 18-2

Supply Current Depends on Clock Frequency


SEE CLOCK.C


Use TMR1 for Sample Clock

• 16 bit (65536)• Count up• Flag or interrupt for FFFF to 0000 transition• Ticks every instruction cycle (every 4

oscillator cycles)– If 8 MHz oscillator, ticks every 0.5 uS– 0.5 x 65536 = 32.768 mS

• Prescaler for slower ticks– 1, 2, 4, 8


Sampling Clock Example

• Sensor sampling at 100 Hz• T = 10.00 mS• 8 MHz oscillator, 0.5 uS ticks• 10.00 mS = 20,000 ticks• 65536 – 20000 = 45546, load this into

TMR1


CCS Code#define BASECOUNT 45536setup_timer_1(T1_INTERNAL | T1_DIV_BY_1);set_timer1(BASECOUNT)enable_interrupts(INT_RTCC);enable_interrupts(GLOBAL);

#int_timer1void timer1_isr(void){

set_timer1(BASECOUNT); ...sample data...

}


OP AMPS


IMPLEMENTING REAL-TIME CONTROL ALGORITHMS


Feedback Control System

Σ

SENSOR

SYSTEM

+

-

OUTPUTINPUT eCONTROLLER


Sampling Matters


Digital Control Hardware


Algorithms


Digital algorithm structure

Sample 10-20 times faster than desired closed-loop bandwidth

Need fast computation engine for rapid control. Fast multiply/add.

2413121 *** −−− +++= kkkkk ukukekeku

k k ke r y= −

1 1 2( , , , , , )k k k k ku f e e u u− − −= ⋯ ⋯

error

sample k

control


P Control

Analog P stable, digital P can go unstable

*k ku k e=


PID Control


PID


Pseudo Codeinit

k1 = kp + kd/Tk2 = kd/Tk3 = ki*Tem1 = 0setclock(period)startclock()

while (TRUE) {waitfortick()r = getinput()y = getoutput()e = r – yie = ie + eif (ie > iemax) ie = iemaxif (ie < -iemax) ie = -iemaxu = k1*e – k2*em1 + k3*ieif (u > umax) u = umaxif (u < -umax) u = -umaxsendcmd(u)em1 = e

See Dlab code for example


PATENTS


Utility Patents

1. New2. Useful3. Non-obvious


Search

• uspto.gov• Google Patents

• Search by class• Read the claims• Keywords may not be obvious

Tips


IP Steps

• Invention disclosure• Provision Patent Application• Utility Patent Application• Issued Patent

http://www.research.umn.edu/techcomm/index.htm

http://www.uspto.gov/web/offices/pac/provapp.htm


A PRACTICAL INTRODUCTION TO WIRELESS COMMUNICATION

FOR SMART PRODUCTS


Key Specifications

• Transmission distance• Power required (Xmt & Rcv)• Uni or bidirectional• Data rate (bits or bytes per sec)• Error rate (reliability)• Antenna logistics• Communication band• Physical size• Ease of use• Cost

RADIORADIO


Main Types

• RF (radio frequency)• Infrared• Light beam• Ultrasound


Networks

• Single path– 1-way– 2-way

• Multiple nodes– Star– Bus– Ring– Mesh

RADIORADIO RADIORADIORADIORADIO

Wikipedia: Network Topologies


Infrared• Lowest cost wireless• Line of sight• 40 KHz modulated signal• Data protocol varies by

manufacturer• Control your device with a TV

remote

Sharp GP1UM28YK00F

www.sbprojects.com/knowledge/ir/ir.htm

users.telenet.be/davshomepage/

en.wikipedia.org/wiki/Consumer_IR


RF Wireless• Industrial, scientific and medical (ISM) radio bands

– Cordless phones, RFID tags, Bluetooth, Zigbee, WiFi– No license if low-power

• Wireless link without protocol• Wireless link with protocol

– Wi-Fi (802.11)• High data rate, high power• Full-scale, Local Area Network (LAN)• Setup and configuration takes computational horsepower

– Bluetooth (802.15.1)• Short range, lower power• 2.4 GHz, 1 Mb/s• Class 1: 100 mW, 300 ft; Class 2: 2.5 mW, 30 ft, Class 3: 1 mW, 3 ft• Part of Wireless Personal Area Networks (WPAN)• For connecting peripherals (“the wireless serial port”), “pairing”

– Zigbee (802.15.4)• Short range, low power, low cost applications• 2.4 GHz, 250 Kb/s• Star or mesh networks, self-organizing• WPAN applications

– Ultra-wideband• High data rate, time-of-flight measures

– RFID• Very short range, passive tag, low data rate


Linx AN-100


Digital Coding

• Amplitude-shift keying (ASK)– Absence of carrier = 0, carrier

= 1– Also called OOSK (On-Off Shift

Keying), OOK (On-Off Keying) and CPCA (Carrier-Present Carrier-Absent)

– Low cost, low power, low data rate, poor noise immunity

• Frequency-shift keying (FSK)– Space frequency = 1, mark

frequency = 0– Higher data rate, better noise

immunity, higher power, higher cost

Linx AN 130


ASK Data Rate Limitations

Linx AN 232


Linx AN 160


Error Detection

• Parity Check– Add all the 1’s, determine if sum even or odd,

check against parity bit– Example: data = 10101010, send = 101010101,

receive = 001010101, error so discard– Can’t catch dual errors

• Checksum– Add all bytes in the data frame, send sum as final

checksum byte

• Cyclic Redundancy Check– Like checksum but more reliable

Ref: Linx AN 160


Protocol Layers: ZigBee Example

www.microchip.com


Packaged Solutions


315, 418, 433.92 MHz Transmitter/Receiver Pairs

• Serial at 2400, 4800 baud

• One-way• No error checking, no

protocol• ASK transmission• Simple and low cost• laipac.com via

sparkfun.com


Linx LT Series Transceiver

• 315, 418, 433 MHz

• 3,000 ft• Two-way

• Transmit 12 mA, receive 6.1 mA

Parallax 433 MHz Transceiver(Linx TRM-433-LT)1200-9600 bps250 ft.Transmit 12 mA, receive 6.1 mA$40


Linx Transmitter/Receiver With Encoder/Decoder

• 315, 418, 433 Mhz

• 8 switch channels• 3,000 ft

• 1.5 mA transmit


Bluetooth

Roving Networks RN-41 via Sparkfun


XBee Zigbee

XBee modules via Sparkfun, Parallax, Digi-Key


TI MSP430 + Radio

• MSP430 low-power microcontroller

• CC2500 RF transceiver– 2.4 GHz ISM band– 250 Kbps– RCV 18 mA– XMT 21 mA

• $50


Microchip MRF24J40 Radio

• 2.4 GHz• 802.15.4 compliant• ZigBee, MiWi (Microchip simplified

802.15.4)

Microchip.com


Comparing RF Solutions

50

35

6.1

3.5

RCV Power (ma)

45

65

12

11

XMTPower (ma)

WiFi

$38100250KXBee(Parallax)

Zigbee

$683302MRN41 (Sparkfun)

Bluetooth

$34

($80)

2509600Linx LT series (Parallax)

Plain Link

$105004800Laipacseries

Plain Link

Cost per link

Distance (ft)

Data Rate (bps)

ProductTechnology


Implementation Tips

• Look for solutions that appear as a serial port on the application side

• For testing, transmit a counter and monitor the received data

• FCC regulations – See “FCC Regulation Guide” at

linxtechnologies.com


References

• Linx Technologies App Notes– 100, RF 101 Information for the RF Challenged

– 160, Considerations For Sending Data Over a Wireless Link– 130, Modulation Techniques For Low-Cost RF Data Links

– 500, Antennas: Design, Application, and Performance

www.linxtechnologies.com

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