Data Acquisition System Using ATmega8

8/9/2019 Data Acquisition System Using ATmega8

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Data Acquisition System using

ATmega8

Under the Guidance of

Mrs. Neeta Mehta Mam

&

Ms.

Sunil S Pillai

Department of Electronics & Communications

Government Engineering College, Sector-26Gandhinagar

October 2008


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ACKNOWLEDGEMENT

Before we get into thick of the thing, I would like to add a few heartfelt words

for the people who have been behind this document.

First of all, few words for the Almighty God for showering his choicest

blessings on me and enabling me to complete this Project report well in time and with

desired quality.

I would like to voice my sincere thanksgiving to Mrs. Neeta Maam Head of

Electronics and Communication Engineering Department and to Ms., Subject In

charge, for providing us with such a high potential opportunity. I hope I have utilized

it to the best of your expectation.

In continuance, I would like to mention about my parents. Thank you Mom

and Dad for your continued encouragement and guidance.

Finally I would like to express my gratitude to all my classmates for their

constant feedback and support in improving this document and making it more reader

friendly. Lastly I do not intend to forget all the people who painstakingly read the

entire manuscript and provided valuable inputs to make it free from errors.

Thanking You All.

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INDEX

1) Introduction 4

2) Project Description

3) Hardware Section

4) Circuit Diagram 5

5) Parts List

6) Microcontroller Program 7

7) Software Section

8) PC-Board HandShake

9) Appendix A: AVR Source Code

10) Appendix B: AVR HEX FILE

11) Appendix C: Datasheet 8

12) Applications 15

13) Bibliography 16

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INTRODUCTION

We can use a PC for connecting the homemade data acquisition hardware and

produce the GUI for user friendly graphical presentation easily.

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PROJECT DESCRIPTION

In this project we use a PC for GUI display and the homemade data converter

board using the AVR microcontroller. The circuit is built with the ATmega8. The

chip has the on chip 10-bit resolution A/D Converter. Temperature sensor are

connected to the 6 channels ADC input. You can connect up to 8 sensors with the

ATmega8 TQFP package. The analog inputs are captured by sending a command

from PC. The readings will display graphically or text data. The data can also berecorded as the database.

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HARDWARE

The complete hardware schematic for the ADC board is shown below. The

board consists of the ATmega8, the temperature sensor (LM335), and the serial

interface. The on chip firmware controls reading the ADC converter, receives

commands from PC and sends the reading to PC. The microcontroller is running with

8MHz crystal oscillator, if we use the internal RC oscillator, the external crystal may

be omitted. The ATmega8 DIP version has 6 channels analog input. If you need up to

8 ADC input, you can use ATmega8 in TQFP package, or you can use another AVR

microcontroller with the on-chip ADC.

We use LM335 temperature sensor. It can measure the temperature using two

wires remotely. The chip produces an output signal that is proportional to the Celsius

temperature scale. The trimmer POT is used to calibrate the correct output voltage at

known temperature, for example 2.98V @ 25 C.

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CIRCUIT DIAGRAM

.

7

Temperatu

reLoggerhardwaresc

hematic


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PARTS LIST

The circuit is built around Atmega8 and a max232 serial Interface.

It works off a 12V DC, 500mA power supply. You can also power the circuitfrom mains by using a 12V DC, 500mA adaptor in place of the 12V DC power supply.

Semiconductors

U1 Atmega8 Microcontrroller U2 MAX232 Serial Controller

T1 LM335A Temperature Sensor

Resistors(All - Watt +- 5% Carbon unless stated otherwise )

R1, 1 Kilo Ohm

R2, 10 Kilo Ohm

Capacitors

C1, C2, C3, C4 1 uF Ceramic Disc

C5 10 uF

C6,C7,C8 100 nF

C9,C10 22 pF

Miscellaneous

LED Red LEDL Inductor 10 uH

X Crystal, 8Mhz

S1 Push Button Switch

DB9 Connector

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MICROCONTROLLER PROGRAM

The AVR program was written in assembly language. It can be fed into AVR

Studio to generate the Hex File. The Detailed Source Code has been Listed in

Appendix-A. The Generated Hex File is given in Appendix-B. In case of non

availability of Cross Compilers, the Hex file can directly be loaded into Atmega8.

The main code running waits the serial command from PC. The speed is set

to19200 8n1 format. If the board receives character '>', the AVR must echo the

character '>' to the PC. This step is used to check the hardware is connected or not.

Another command is 'r' (read), the microcontroller reads 8 channel ADC and sends

them to PC serially.

If you have only 6 channel, for last channel (ADC6 and ADC7), you can

modify the source code so the microcontroller will send a dummy value. These values

will be ignored by PC software. Or if you want to ignore another channel from PC

logging, just fill ADC values with dummy into their field. The descriptions have been

commented in the source code. You may modify the source code easily.

The main loop has been given below for a close look at logic:

mainloop: sbis USR,RXC ;test RXC bit

rjmp mainloop ;none available, wait

in mpr,UDR

cpi mpr,'>'brne _cmdr

rcall txchar

rjmp mainloop

_cmdr: cpi mpr,'r'

brne mainloop

readadc: cbi PORTD,4

ldi mpr,13

rcall txchar

ldi mpr,'D'

rcall txchar

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_readadc0: ldi mpr,0b01000000 ;set ADMUX int ref ch0

out ADMUX,mpr

rcall readadcave

rcall sendvalue


out ADMUX,mpr

rcall readadcave

rcall sendvalue

. . . . . . .

. . . . . . .

. . . . . . .

. . . . . . .

_readadc5: ldi mpr,0b01000101 ;set ADMUX int ref ch5out ADMUX,mpr

rcall readadcave

rcall sendvalue


out ADMUX,mpr

rcall readadcave

ldi mpr,0xFF ;these 4 lines to disable ADC6

mov rbin1H,mpr ;(in DIP version)

ldi mpr,0xFF ;ADC6 = 0xFFFF

mov rbin1L,mpr ;dummy value

rcall sendvalue


out ADMUX,mpr

rcall readadcave





rcall sendvalue

sbi PORTD,4

rjmp mainloop

adcparstr: .db "ADC parameter :",13,10,0

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SOFTWARE

A Graphical User Interface (GUI) Application has been build to operate the

Board from PC. After Connecting the Hardware to Serial Port, the application can beinvoked to accept the incoming Data.

Features of the PC Logger software are as follows.

Adjustable sampling interval,

Real time view in single graph or multiple graph,

Record the data, save, and open the recorded database,

Get statistically reading, print the record and graph (or export it as the

metafile, JPG),

Serial control window for monitoring and manually data transfer.

The full version PC software is designed for capturing up to 16 channels. In this

version, the PC software will read 8 channels. For the ATmega8 in DIP version, it can

display only 6 channels.

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The PC Logger GUI has been build with Borland C++ Builder 4.

dll for BDE, Borland Database Engine

- bantam.dll

- idapi32.dll

- idbat32.dll

- idpdx32.dll

- idr20009.dll

- idsql32.dll

Core BDE Files

--------------

IDASCI32.DLL For accessing ASCII files

IDBAT32.DLL For batch movement of data

IDDA3532.DLL For accessing Microsoft Access databases

IDDAO32.DLL For accessing Microsoft Access databases

IDDBAS32.DLL For accessing dBASE databases

IDDR32.DLL For Data Repository (Paradox only)

IDODBC32.DLL For BDE access to ODBC drivers

IDPDX32.DLL For accessing Paradox databases

IDQBE32.DLL QBE query engine

IDR20009.DLL BDE resources

IDAPI32.DLL Main BDE system DLL

IDSQL32.DLL SQL query engine (including local SQL)

IDPROV32.DLL For MIDAS providers

Language Driver Files

---------------------

BANTAM.DLL Internationalization engine

*.CVB Character set conversion files

*.BTL Locales

BLW32.DLL Expression engine

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SCREENSHOT

13

Mainscre

enofDataAcquisitionp

rogr

am


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PC-BOARD HANDSHAKE

Data transferring between ADC board and PC uses the following protocol .

For the first time connecting, after opening serial port, PC tries to connect the

ADC board. The PC send a character '>' (0x3E) and the board will echo it

back.

After the connection has been established, we can send the command to the

ADC board. For command read, PC sends character 'r' (0x72), and the board

responses with ADC reading as: '\rD' + 2byte(ADC0) + 2byte(ADC1) + +

2byte(ADC7), total 18 bytes length. The reading is 16-bit data, (10-bit

resolution) with high byte send first followed with low byte.

Note :

For real time recording using fast sampling, for example 50ms or 100ms, better view

in a single graph. The display performance depends on the PC speed.

I tested running with 700MHz CPU speed, 128MB RAM, it gives smooth view but

for multiple view, it could not display fast enough.

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APENDIX A

MICROCONTROLLER SOURCE CODE

;-------------------------------------------------------------------------; Read ADC channel

;

;-------------------------------------------------------------------------

.nolist

.include "m8def.inc"

.list

.def rlpm = R0

.def rbin1L = R10

.def rbin1H= R11

.def rbin2L = R12

.def rbin2H= R13

.def mpr = R16

.def var1 = R17

.def var2 = R18

.def var3 = R19

;constants

.equ fq = 8000000 ;xtal frequency, CKSEL3..0 V_VVV

.equ baud = 19200 ; baud rate

.equ baudgen = (fq/ (16*baud))-1 ; baud divider

; Reset-/Interrupt Vector

.CSEG

.org 0x0000

rjmp start

;------------------------------------------------------------------------------------

; Subroutine for string transfer

txstr: sbis USR,UDRE ;wait Tx buff empty

rjmp txstr

lpm ;read next char from prog mem

and rlpm,rlpm ;null = end of string

brne txsend

ret

txsend: lpm ;read the same char again

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out UDR,rlpm ;Tx character read

adiw ZL,1 ;point to next char in memory

rjmp txstr

;-----------------------------------------------------------------------------------

;Transmit charactertxchar: sbis USR,UDRE

rjmp txchar

out UDR,mpr

ret

;----------------------------------------------------------------------------------

;Receive character

rxchar: sbis USR,RXC

rjmp rxchar

in mpr,UDR

ret

;-------------------------------------------------------------------------------------

;Read ADC (var2 + 1) times and get average

readadcave: sbi ADCSR,ADSC

ldi var2,3

_adcave1: sbis ADCSR,ADIF

rjmp _adcave1

sbi ADCSR,ADIF ;clear flag by setting bit

in mpr,ADCL

mov rbin2L,mpr

in mpr,ADCH

mov rbin2H,mpr

_adcave2: sbi ADCSR,ADSC

_adcave3: sbis ADCSR,ADIF

rjmp _adcave3

sbi ADCSR,ADIF ;clear flag by setting bit

in mpr,ADCL

mov rbin1L,mpr

in mpr,ADCHmov rbin1H,mpr

add rbin2L,rbin1L ;add adc(n)+adc(n-1)

adc rbin2H,rbin1H

dec var2

brne _adcave2

lsr rbin2H

ror rbin2L

lsr rbin2H

ror rbin2L

_adcend: mov rbin1H,rbin2H

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mov rbin1L,rbin2L

ret

;-------------------------------------------------------------------------

;Start of program

start: ldi mpr,low(RAMEND)out SPL,mpr

ldi mpr,high(RAMEND)

out SPH,mpr

ldi mpr,baudgen ;baud generator

out UBRRL,mpr ;set divider

ldi mpr,0b00011000 ;enable TX and RX

out UCR,mpr ;to UART Control Register

;PORTB IIOOOIII

ldi mpr,0b00111000out DDRB,mpr

ldi mpr,0b11000111 ;pull-up input

out PORTB,mpr

;PORTC --IIIIII

ldi mpr,0b00000000

out DDRC,mpr

ldi mpr,0b00000000 ;cut pull-up input

out PORTC,mpr

;PORTD IIIOOOIO

ldi mpr,0b00011101

out DDRD,mpr

ldi mpr,0b11100010 ;pull-up input

out PORTD,mpr

sbi PORTD,4

ldi var1,2

delaystartup: rcall delay500ms

dec var1

cpi var1,0brne delaystartup

intro: ldi mpr,12

rcall txchar

ldi ZH,high(adcparstr*2)

ldi ZL,low(adcparstr*2)

rcall txstr

ldi mpr,0b10000010 ;set ADC enable

out ADCSR,mpr

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mainloop: sbis USR,RXC ;test RXC bit

rjmp mainloop ;none available, wait

in mpr,UDR

cpi mpr,'>'

brne _cmdrrcall txchar

rjmp mainloop

_cmdr: cpi mpr,'r'

brne mainloop

readadc: cbi PORTD,4

ldi mpr,13

rcall txchar

ldi mpr,'D'

rcall txchar


out ADMUX,mpr

rcall readadcave

rcall sendvalue


out ADMUX,mpr

rcall readadcave

rcall sendvalue


out ADMUX,mpr

rcall readadcave

rcall sendvalue


out ADMUX,mpr

rcall readadcave

rcall sendvalue


out ADMUX,mpr

rcall readadcave

rcall sendvalue


out ADMUX,mpr

rcall readadcave

rcall sendvalue


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out ADMUX,mpr

rcall readadcave




mov rbin1L,mpr ;dummy valuercall sendvalue


out ADMUX,mpr

rcall readadcave





rcall sendvalue

sbi PORTD,4

rjmp mainloop

adcparstr: .db "ADC parameter :",13,10,0

;--------------------------------------------------------------------------------------------

;ASCII to 2HEX

ascii2hex: push mpr

push mpr

swap mpr

andi mpr,0x0F

cpi mpr,10 ;nibble > 9?

brcs _ascii2hex1 ;no

ldi var1,7 ;add 7 to get hex A to F

add mpr,var1

_ascii2hex1: ldi var1,'0'

add mpr,var1

rcall txcharpop mpr

andi mpr,0x0F

cpi mpr,10 ;nibble > 9?

brcs _ascii2hex2 ;no

ldi var1,7 ;add 7 to get hex A to F

add mpr,var1

_ascii2hex2: ldi var1,'0'

add mpr,var1

rcall txchar

pop mpr

ret

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;------------------------------------------------------------------------------------------

;Delay 500ms @8mhz

delay500ms: push R23

push R24

push R25ldi R23,0x6B

_wg500loop0: ldi R24,0x46

_wg500loop1: ldi R25,0xB1

_wg500loop2: dec R25

brne _wg500loop2

dec R24

brne _wg500loop1

dec R23

brne _wg500loop0

pop R25

pop R24pop R23

ret

;--------------------------------------------------------------------------------------------

;Bin2ToBCD5

;converts a 16-bit-binary to a 5-digit-BCD

;in rbin1H:rbin1L

sendvalue: mov mpr,rbin1H

rcall txchar

mov mpr,rbin1L

rcall txchar

ret

;sendvalue:

bin2tobcd5: push rbin1H ;save number

push rbin1L

ldi mpr,high(10000) ;start with 10.000

mov rbin2H,mpr

ldi mpr,low(10000)

mov rbin2L,mprrcall bin2todigit ;calculate digit

ldi mpr,high(1000) ;next with 1.000

mov rbin2H,mpr

ldi mpr,low(1000)

mov rbin2L,mpr

rcall bin2todigit ;calculate digit

rcall txchar

ldi mpr,high(100) ;next with 100

mov rbin2H,mpr

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ldi mpr,low(100)

mov rbin2L,mpr


rcall txchar

ldi mpr,high(10) ;next with 10mov rbin2H,mpr

ldi mpr,low(10)

mov rbin2L,mpr


rcall txchar

mov mpr,rbin1L ;remainder are ones

ori mpr,0x30

rcall txchar

pop rbin1L

pop rbin1H

ret

;-----------------------------------------------------------------------------------

;Bin2ToDigit

;converts one decimal digit by continued subtraction of a BCD

bin2todigit: clr mpr ;digit count is zero

_bin2todigita: cp rbin1H,rbin2H ;number bigger than decimal?

brcs _bin2todigitc ;MSB smaller than decimal

brne _bin2todigitb ;MSB bigger than decimal

cp rbin1L,rbin2L ;LSB bigger or equal decimal

brcs _bin2todigitc ;LSB smaller than decimal

_bin2todigitb: sub rbin1L,rbin2L ;subtract LSB decimal

sbc rbin1H,rbin2H ;subtract MSB decimal

inc mpr ;increment digit count

rjmp _bin2todigita ;next loop

_bin2todigitc: ori mpr,0x30

ret

;end

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APPENDIX B

HEX FILE

This is the Assembled Hex File. In case of non availability of Cross Compilers, this

Hex file can be directly loaded into Microcontroller.

:020000020000FC

:100000002EC05D9BFECFC895002009F40895C895C9

:100010000CB83196F6CF5D9BFECF0CB908955F9B6F

:10002000FECF0CB10895369A23E0349BFECF349A6C

:1000300004B1C02E05B1D02E369A349BFECF349A2F

:1000400004B1A02E05B1B02ECA0CDB1C2A95A1F775

:10005000D694C794D694C794BD2CAC2C08950FE5C4:100060000DBF04E00EBF09E109B908E10AB908E3D0

:1000700007BB07EC08BB00E004BB00E005BB0DE1DB

:1000800001BB02EE02BB949A12E061D01A951030C7

:10009000E1F70CE0C0DFF1E0E0E1B3DF02E806B930

:1000A0005F9BFECF0CB10E3311F4B5DFF9CF0237F1

:1000B000B9F794980DE0AFDF04E4ADDF00E407B9D1

:1000C000B2DF55D001E407B9AEDF51D002E407B981

:1000D000AADF4DD003E407B9A6DF49D004E407B98D

:1000E000A2DF45D005E407B99EDF41D006E407B999

:1000F0009ADF0FEFB02E0FEFA02E39D007E407B92B

:1001000092DF0FEFB02E0FEFA02E31D0949AC8CF10:1001100041444320706172616D65746572203A0DCF

:100120000A000F930F9302950F700A3010F017E03A

:10013000010F10E3010F6FDF0F910F700A3010F005

:1001400017E0010F10E3010F66DF0F9108957F9311

:100150008F939F937BE686E491EB9A95F1F78A95CE

:10016000D9F77A95C1F79F918F917F9108950B2DC3

:1001700052DF0A2D50DF0895BF92AF9207E2D02ED2

:1001800000E1C02E18D003E0D02E08EEC02E13D010

:1001900042DF00E0D02E04E6C02E0DD03CDF00E0B0

:1001A000D02E0AE0C02E07D036DF0A2D006333DFE1

:1001B000AF90BF9008950027BD1438F011F4AC142F

:0E01C00020F0AC18BD080395F7CF006308953A

:00000001FF

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APPENDIX C

DATASHEETS

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BIBILOGRAPHY

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Data Acquisition System Using ATmega8