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Learn to make simple microcontroller projects, pic, 8051, avr and arm projects. download 8051 projects, tutorials, libraries, sample codes. join the microcontroller discussion forum and ask doubts regarding electronics. the best source for 8051 over internet.en-gb2009-01-08T08:54:51-08:00contact@nospam.comhourly12000-01-01T12:00+00:00ADC 0844 errorneous results. Help me.
http://www.8051projects.net/forum-t11195.html
2009-01-08T08:54:51-08:00Hi everyone, I'm new in the forum. This is a good website.Now, this my problem, the output of the ADC seems to give a weak output ( measured 1.1 V using multimeter). I would appreciate anyone helping Problem Hints :Hardware : AT89S51, ADC 0844 and 1x16 LCDCase 1 : LCD displayed 00 when I include the line "acall clr_mux_add"Case 2 : LCD displayed 05, 04, 00 (randomly )when I exclude the line "acall clr_mux_add"Port 3.0 and 3.1 are connected to separated LEDs, so I can observed the program flow, that's all.I programed the ADC based on the timing diagram given in the datasheet. (at the bottom of page)From calculation, I should get 15 or 14 decimal displayed on my LCD, but I get 05 instead, I suspected this is because it displayed the MUX Address.15 decimal = 0000 1111 b (but the 1's are measured to be 1.1 V)Thanks for reading. CODE: WR_adc equ P3.5 RD_adc equ P3.7 DAT_ADC equ P2 ;ADC data pins P2
mux_add : setb P2.0 ;this configuration is using channel 2 single ended clr P2.1 setb p2.2 clr P2.3 ret
clr_mux_add : clr P2.0 clr P2.1 clr P2.2 clr P2.3 retRe: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00Ajaytry using interrupt..you are wasting more time on making LEDs low high so interrupt will solve your problemRe: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00Freddyaaa, thanks for idea.... is there any other way ?Re: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00FreddyHi again, i've found the solution ( i think so) , all i did is add the highlighted line (compare with code above).all thx to : http://www.8051projects.net/downloads84.html because on page 59, i found this :if it wasn't for Ajay, i wouldn't go hay-wire finding info about interrupts... hahaha , so thx Ajay.now, the temperature displayed a more "make sense" value. Now i only use 0.5 sec of temperature sampling.New problem : The temperature reading is not so stable. It changes to different value too rapidly. So, any engineering ideas are seriously welcomed !!Re: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00Arun Kumar Vhi freddy,acall clear_lcdwhy are you clearing the LCD every time in start loop ? if you are using two channels then one channel reading can be placed on line 1 and other channel data on line 2 of lcd.if you are using only one ch, then you need not clear the LCD every time.ArunRe: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00FreddyI only use 1 channel of the ADC.When i remove the acall clear_lcd , the display would be continuous.Something like this : 100F0F10 or maybe i understood u wrongly ??Re: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00Arun Kumar VHi Freddy,you have posted only part of the code, pl.post full code so that we can analyze other subroutines and find the error.since you are using 1 ch and not switching between channels, it is not required to clear the LCD after every cycle.ArunRe: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00Freddyowh okok, sorry about that. I'm just a beginner. CODE: ;Information : ;the code is initilaise as 2x16 although it is 1x16 ;because of the 8+8 configuration. ;the ninth position start at the address 40h ;[00 01 02 03 04 05 06 07 41 42 43 44 45 46 47] ;#07h --> shift display to the left ORG 0000H
mov P2, 0xFF ;configure to read from port 2 acall read_adc acall byte_to_bcd acall write_text ;display upper nibble mov A, r0 ;display lower nibble acall write_text acall delay_500ms sjmp start
conv_adc : clr wr_adc nop mov dat_adc, mux_add ;load mux address into A nop setb wr_adc wait : jb intr_adc, wait ret
read_adc : clr rd_adc nop mov A, DAT_ADC ;move ADC 8 bit result to A nop setb rd_adc nop ret ;========================================================== ;this subroutine converts 8-bit data to bcd ;both high nibble and low nibble are in hex value ;input is taken from A ;the output high nibble is A (hex value) ;the output low nibble is in r0 (also hex value) byte_to_bcd: MOV R0,A ANL A,#0Fh ADD A,#0F6h JNC byte_to_bcd_2 ADD A,#07h byte_to_bcd_2: ADD A,#3Ah XCH A,R0 SWAP A ANL A,#0Fh ADD A,#0F6h JNC byte_to_bcd_3 ADD A,#07h byte_to_bcd_3: ADD A,#3Ah RET ;=========================================================== WAIT_LCD : acall DELAY_2ms RET
WRITE_TEXT : clr en_lcd SETB RS_lcd clr rw_lcd MOV DAT_lcd, A SETB EN_lcd acall DELAY_2ms CLR EN_lcd aCALL WAIT_LCD RET ;=========================================================================== ;Delay subroutines... DELAY_50us: MOV R5, #1 ;this is a 50 micro second delay subroutine REPEAT_4:MOV TH0, #0xFF MOV TL0, #0xD2 SETB TR0 BACK_4: JNB TF0, BACK_4 CLR TR0 CLR TF0 DJNZ R5, REPEAT_4 RET
DELAY_33ms: MOV R5, #100 ;this is a 33 mili second delay subroutine REPEAT_3:MOV TH0, #0xFE MOV TL0, #0xCF SETB TR0 BACK_3: NB TF0, BACK_3 CLR TR0 CLR TF0 DJNZ R5, REPEAT_3 RET
DELAY_2ms: MOV R5, #100 ;this is a 2ms delay subroutine REPEAT: MOV TH0, #0xFF MOV TL0, #0xEE SETB TR0 BACK: JNB TF0, BACK CLR TR0 CLR TF0 DJNZ R5, REPEAT RET
DELAY_500ms: MOV r5, #100 ;this is a 0.5 second delay subroutine REPEAT_2:MOV TH0, #0xEE MOV TL0, #0x00 SETB TR0 BACK_2: JNB TF0, BACK_2 CLR TR0 CLR TF0 DJNZ r5, REPEAT_2 RET
DELAY_1sec: MOV R5, #100 ;this is a 1 second delay subroutine REPEAT_1:MOV TH0, #0xD8 MOV TL0, #0xF0 SETB TR0 BACK_1: JNB TF0, BACK_1 CLR TR0 CLR TF0 DJNZ R5, REPEAT_1 RET END Re: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00Arun Kumar VHi Freddy, first things first :mov P0, #00hmov P1, #00hmov P2, #00hmov P3, #00hthis is a big No-No, on reset all the ports are 0FFh by default so lets keep it that way.in subroutine byte_to_bcd:ADD A,#3Ah it should be #30H ( since you are converting into Ascii for sending it to LCD), also i doubt if this routine is right, bcoz to display FFh you need 3 digits in BCD i,e 255 but you are displaying only 2 digits ( A & R0)you can use the following routine, which converts 1 byte Hex to 3 digit decimal ( you need to declare the variables - hundreds, tens & ones):CODE:Bin2Dec: mov b,#100d div ab mov hundreds,a mov a,b mov b,#10d div ab mov tens,a mov ones,b ret and when dispatching to LCD, just add or ORL #30h to hunds, tens & ones in the DELAY_1sec rountine, MOV TH0, #0xD8 MOV TL0, #0xF0the timer reload values are wrong, you haven't mentioned the xtal Freq but i guess you are using 11.0592Mhzit should be : CODE:MOV TH0,#0DCH ; 10mSec X 100(R5) = 1000mS MOV TL0,#00Hmake these changes and check if the LCD displays correctly PS: i hope the interfacing sequence to the ADC is correct ( write/read ).All the Best !ArunRe: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00Freddywow Arun, now I can display the results in decimal value instead of hex. Thanks I recalculate the formula, I still think that my 1 second delay is correct. I'm using 11.0592 MHz100 x (65536-55536) x 1.085 us = 1.085 sec ( approx. 1 sec) (1/11.0592 Mhz) / 12 = 921,600 Hz 1 / 921,600 = 1.085 us D8F0h = 55536 Now, my problem is :The temperature reading is fluctuating from 14-18 at room temperature ( i set Vref of ADC to Vcc=4.9 V). From calculation, I should get 15 or 16. I suspected this is because of I didn't have any signal conditioning circuit for the ADC analog input. Can this be the problem ?? Vin is from LM35 temp sensor = 0.29 Vstepsize for ADC = 4.90 V / 256 = 19 mVDout is in decimal0.29 / 19mV = 15.263 CODE: ;Information : ;the code is initilaise as 2x16 although it is 1x16 ;because of the 8+8 configuration. ;the ninth position start at the address 40h ;[00 01 02 03 04 05 06 07 41 42 43 44 45 46 47] ;#07h --> shift display to the left ORG 0000H
MOV TMOD, #0x01
RS_lcd EQU P1.2 RW_lcd EQU P1.1 EN_lcd EQU P1.0 DAT_lcd EQU P0 ;LCD PORT for DB0 to DB7
acall delay_500ms sjmp start ;==================================================== Bin2Dec: mov b,#100d ;1100 0100 div ab mov hundreds,a mov a,b mov b,#10d div ab mov tens,a mov ones,b ret ;============================================= ascii4lcd_tens : add A, #30h ;add 30h to tens value ret
ascii4lcd_ones : mov A, B add A, #30h ret ;========================================================= conv_adc : clr wr_adc nop mov dat_adc, mux_add ;load mux address into A nop setb wr_adc wait : jb intr_adc, wait ret
read_adc : clr rd_adc nop mov A, DAT_ADC ;move ADC 8 bit result to A nop setb rd_adc nop ret ;========================================================== ;=========================================================== WAIT_LCD : acall DELAY_2ms RET
WRITE_TEXT : clr en_lcd SETB RS_lcd clr rw_lcd MOV DAT_lcd, A SETB EN_lcd acall DELAY_2ms CLR EN_lcd aCALL WAIT_LCD RET ;=========================================================================== ;Delay subroutines... DELAY_50us: MOV R5, #1 ;this is a 50 micro second delay subroutine REPEAT_4: MOV TH0, #0xFF MOV TL0, #0xD2 SETB TR0 BACK_4: JNB TF0, BACK_4 CLR TR0 CLR TF0 DJNZ R5, REPEAT_4 RET
DELAY_33ms: MOV R5, #100 ;this is a 33 mili second delay subroutine REPEAT_3: MOV TH0, #0xFE MOV TL0, #0xCF SETB TR0 BACK_3: JNB TF0, BACK_3 CLR TR0 CLR TF0 DJNZ R5, REPEAT_3 RET
DELAY_2ms: MOV R5, #100 ;this is a 2ms delay subroutine REPEAT: MOV TH0, #0xFF MOV TL0, #0xEE SETB TR0 BACK: JNB TF0, BACK CLR TR0 CLR TF0 DJNZ R5, REPEAT RET
DELAY_500ms: MOV r5, #100 ;this is a 0.5 second delay subroutine REPEAT_2: MOV TH0, #0xEE MOV TL0, #0x00 SETB TR0 BACK_2: JNB TF0, BACK_2 CLR TR0 CLR TF0 DJNZ r5, REPEAT_2 RET
DELAY_1sec: MOV R5, #100 ;this is a 1 second delay subroutine REPEAT_1: MOV TH0, #0xD8 MOV TL0, #0xF0 SETB TR0 BACK_1: JNB TF0, BACK_1 CLR TR0 CLR TF0 DJNZ R5, REPEAT_1 RET END Re: ADC 0844 errorneous results. Help me.
http://www.8051projects.net/forum-t11195.html
2009-01-08T08:54:51-08:00Arun Kumar VHi Freddy,I recalculate the formula, I still think that my 1 second delay is correct. I'm using 11.0592 MHzyour calculation is based on 12Mhz crystal freq, my guess proved correct that you are using 11.0592Meg xtal.so here is the calculation for 10mSec delay using 11.0592 meg ( 10mS X 100 times =1sec):1) 10,000 divided by 1.085uS = 9216 decimal2) 65536 - 9216 = 56,320 decimal3) 56,320 d = 0DC00h4) TH0 = 0DCh , TL0 = 00hyou can cross check by multiplying 9216 X 1.085 = 9999.36 uSec but your values give a delay of 10,000 X 1.085 = 10,850 uSec a delay about the variation in reading, i'll find let you where the error isArunRe: ADC 0844 errorneous results. Help me.
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2009-01-08T08:54:51-08:00FreddyYup, got it now. Thank you so much Arun I think I'll switch to 12 MHz