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rtracy
Joined: 13 Oct 2005
Posts: 7
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| Help with 16F877A and ADC |
 Posted: Thu Oct 13, 2005 1:23 pm |
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I'm trying to write a basic program that will show that ADC is working on a PICDEM 2 board. I'd like to see a 5VDC signal on RA0 light RB3 and then scaled down from there. Using the variable resistor connected to RA0 I can vary the voltage from 0 to 5. No matter what values I use in the program, .350VDC will light RB3. What am I doing wrong?
| Code: |
void main()
{
long value;
int loop;
setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL);
setup_psp(PSP_DISABLED);
setup_spi(FALSE);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
while (true){
set_adc_channel(0);
delay_ms(5);
value = read_adc();
delay_ms(200);
if (value >= 2){
output_high(pin_b0);}
if (value < 2) {
output_low(pin_b0);}
if (value >= 100){
output_high(pin_b1);}
if (value < 100) {
output_low(pin_b1);}
if (value >= 512){
output_high(pin_b2);}
if (value < 512) {
output_low(pin_b2);}
if (value >= 1001){
output_high(pin_b3);}
if (value < 1001) {
output_low(pin_b3);}
}
}
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tophe59
Joined: 13 Oct 2005
Posts: 32
Location: France
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| Posted: Thu Oct 13, 2005 1:27 pm |
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I think the ADS is 10bits but the read is 8bits.
edit : have you test with 0 and 5vdc ? |
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rtracy
Joined: 13 Oct 2005
Posts: 7
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| Posted: Thu Oct 13, 2005 1:41 pm |
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| tophe59 wrote: | I think the ADS is 10bits but the read is 8bits.
edit : have you test with 0 and 5vdc ? |
Yes, I've tested with 0 and 5VDC. I've even tried using the external voltage references with the same results.
I added a #device adc=10 with the same results. |
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newguy
Joined: 24 Jun 2004
Posts: 1903
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| Posted: Thu Oct 13, 2005 1:47 pm |
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Just for the heck of it, replace "long value;" with "int16 value;". Make sure the #device adc=10 stays.
If that doesn't work, then try it with the adc set to 8 bits. You'll have to change "value" to be an 8 bit variable, and you'll need to change your comparison limits too. |
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rtracy
Joined: 13 Oct 2005
Posts: 7
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| Posted: Thu Oct 13, 2005 2:55 pm |
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I changed the ADC channel from 0 to 1 and it works fine. I haven't the slightest idea why it won't work correctly on channel 0.
set_adc_channel(0);
I'd really like to know what's going on if anyone has an idea.
Thanks. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Oct 13, 2005 3:05 pm |
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Post your compiler version and also post what PIC you're using.
Your compiler version can be found at the top of the .LST file in
the project directory. It will be a number like 3.191, or 3.236, etc. |
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rtracy
Joined: 13 Oct 2005
Posts: 7
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| Posted: Thu Oct 13, 2005 4:01 pm |
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| PCM programmer wrote: | Post your compiler version and also post what PIC you're using.
Your compiler version can be found at the top of the .LST file in
the project directory. It will be a number like 3.191, or 3.236, etc. |
PIC16F877A-I/P
| Code: |
CCS PCM C Compiler, Version 3.206, 24798 13-Oct-05 15:37
Filename: C:\Temp\test.LST
ROM used: 197 words (2%)
Largest free fragment is 2048
RAM used: 9 (5%) at main() level
10 (6%) worst case
Stack: 1 locations
*
0000: MOVLW 00
0001: MOVWF 0A
0002: GOTO 019
0003: NOP
.................... #include "C:\Temp\test.h"
.................... #include <16F877.h>
.................... //////// Standard Header file for the PIC16F877 device ////////////////
.................... #device PIC16F877
.................... #list
....................
.................... #device adc=8
.................... #use delay(clock=4000000)
0004: MOVLW 24
0005: MOVWF 04
0006: MOVF 00,W
0007: BTFSC 03.2
0008: GOTO 018
0009: MOVLW 01
000A: MOVWF 78
000B: CLRF 77
000C: DECFSZ 77,F
000D: GOTO 00C
000E: DECFSZ 78,F
000F: GOTO 00B
0010: MOVLW 4A
0011: MOVWF 77
0012: DECFSZ 77,F
0013: GOTO 012
0014: NOP
0015: NOP
0016: DECFSZ 00,F
0017: GOTO 009
0018: RETLW 00
.................... #fuses NOWDT,HS, NOPUT, NOPROTECT, BROWNOUT, NOLVP, NOCPD, NOWRT, NODEBUG
....................
....................
....................
....................
.................... void main()
.................... {
0019: CLRF 04
001A: MOVLW 1F
001B: ANDWF 03,F
001C: BSF 03.5
001D: BSF 1F.0
001E: BSF 1F.1
001F: BSF 1F.2
0020: BCF 1F.3
.................... long value;
.................... int loop;
....................
.................... setup_adc_ports(ALL_ANALOG);
*
0024: BSF 03.5
0025: BCF 1F.0
0026: BCF 1F.1
0027: BCF 1F.2
0028: BCF 1F.3
.................... setup_adc(ADC_CLOCK_INTERNAL);
0029: BCF 03.5
002A: BSF 1F.6
002B: BSF 1F.7
002C: BSF 03.5
002D: BCF 1F.7
002E: BCF 03.5
002F: BSF 1F.0
.................... setup_psp(PSP_DISABLED);
0030: BSF 03.5
0031: BCF 09.4
.................... setup_spi(FALSE);
*
0021: MOVLW FF
0022: BCF 03.5
0023: MOVWF 20
*
0032: BCF 03.5
0033: BCF 14.5
0034: BCF 20.5
0035: MOVF 20,W
0036: BSF 03.5
0037: MOVWF 07
0038: BCF 03.5
0039: BSF 20.4
003A: MOVF 20,W
003B: BSF 03.5
003C: MOVWF 07
003D: BCF 03.5
003E: BCF 20.3
003F: MOVF 20,W
0040: BSF 03.5
0041: MOVWF 07
0042: MOVLW 00
0043: BCF 03.5
0044: MOVWF 14
0045: BSF 03.5
0046: MOVWF 14
.................... setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
0047: MOVF 01,W
0048: ANDLW C0
0049: IORLW 08
004A: MOVWF 01
.................... setup_timer_1(T1_DISABLED);
004B: BCF 03.5
004C: CLRF 10
.................... setup_timer_2(T2_DISABLED,0,1);
004D: MOVLW 00
004E: MOVWF 78
004F: MOVWF 12
0050: MOVLW 00
0051: BSF 03.5
0052: MOVWF 12
....................
....................
.................... while (true){
....................
.................... set_adc_channel(1);
0053: MOVLW 08
0054: MOVWF 78
0055: BCF 03.5
0056: MOVF 1F,W
0057: ANDLW C7
0058: IORWF 78,W
0059: MOVWF 1F
.................... delay_ms(5);
005A: MOVLW 05
005B: MOVWF 24
005C: CALL 004
.................... value = read_adc();
005D: BSF 1F.2
005E: BTFSC 1F.2
005F: GOTO 05E
0060: MOVF 1E,W
0061: CLRF 22
0062: MOVWF 21
.................... delay_ms(200);
0063: MOVLW C8
0064: MOVWF 24
0065: CALL 004
....................
....................
.................... if (value >= 2){
0066: MOVF 22,F
0067: BTFSS 03.2
0068: GOTO 06D
0069: MOVF 21,W
006A: SUBLW 01
006B: BTFSC 03.0
006C: GOTO 071
.................... output_high(pin_b7);}
006D: BSF 03.5
006E: BCF 06.7
006F: BCF 03.5
0070: BSF 06.7
.................... if (value < 2) {
0071: MOVF 22,F
0072: BTFSS 03.2
0073: GOTO 07C
0074: MOVF 21,W
0075: SUBLW 01
0076: BTFSS 03.0
0077: GOTO 07C
.................... output_low(pin_b7);}
0078: BSF 03.5
0079: BCF 06.7
007A: BCF 03.5
007B: BCF 06.7
....................
.................... if (value >= 100){
007C: MOVF 22,F
007D: BTFSS 03.2
007E: GOTO 083
007F: MOVF 21,W
0080: SUBLW 63
0081: BTFSC 03.0
0082: GOTO 087
.................... output_high(pin_d1);}
0083: BSF 03.5
0084: BCF 08.1
0085: BCF 03.5
0086: BSF 08.1
.................... if (value < 100) {
0087: MOVF 22,F
0088: BTFSS 03.2
0089: GOTO 092
008A: MOVF 21,W
008B: SUBLW 63
008C: BTFSS 03.0
008D: GOTO 092
.................... output_low(pin_d1);}
008E: BSF 03.5
008F: BCF 08.1
0090: BCF 03.5
0091: BCF 08.1
....................
.................... if (value >= 120){
0092: MOVF 22,F
0093: BTFSS 03.2
0094: GOTO 099
0095: MOVF 21,W
0096: SUBLW 77
0097: BTFSC 03.0
0098: GOTO 09D
.................... output_high(pin_d0);}
0099: BSF 03.5
009A: BCF 08.0
009B: BCF 03.5
009C: BSF 08.0
.................... if (value < 120) {
009D: MOVF 22,F
009E: BTFSS 03.2
009F: GOTO 0A8
00A0: MOVF 21,W
00A1: SUBLW 77
00A2: BTFSS 03.0
00A3: GOTO 0A8
.................... output_low(pin_d0);}
00A4: BSF 03.5
00A5: BCF 08.0
00A6: BCF 03.5
00A7: BCF 08.0
....................
.................... if (value >= 200){
00A8: MOVF 22,F
00A9: BTFSS 03.2
00AA: GOTO 0AF
00AB: MOVF 21,W
00AC: SUBLW C7
00AD: BTFSC 03.0
00AE: GOTO 0B5
.................... output_high(pin_c3);}
00AF: BCF 20.3
00B0: MOVF 20,W
00B1: BSF 03.5
00B2: MOVWF 07
00B3: BCF 03.5
00B4: BSF 07.3
.................... if (value < 200) {
00B5: MOVF 22,F
00B6: BTFSS 03.2
00B7: GOTO 0C2
00B8: MOVF 21,W
00B9: SUBLW C7
00BA: BTFSS 03.0
00BB: GOTO 0C2
.................... output_low(pin_c3);}
00BC: BCF 20.3
00BD: MOVF 20,W
00BE: BSF 03.5
00BF: MOVWF 07
00C0: BCF 03.5
00C1: BCF 07.3
....................
.................... }
00C2: BSF 03.5
00C3: GOTO 053
.................... }
....................
....................
....................
....................
....................
....................
....................
00C4: SLEEP
Configuration Fuses:
Word 1: 3F7A HS NOWDT NOPUT NOPROTECT BROWNOUT NOLVP NOCPD NOWRT NODEBUG
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Oct 13, 2005 4:39 pm |
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I took your code and compiled it with PCM 3.206, and ran it on
a 16F877A on a PicDem2-Plus board. I did change the output pins
from the ones you're using, back to the LED pins of B0, B1, B2, and B3.
Then as I turn the trimpot on the board, the LEDs progressively turn on,
and then as I turn it the other way they progressively turn off.
So it works for me.
Maybe you accidently damaged pin A0 ? |
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rtracy
Joined: 13 Oct 2005
Posts: 7
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| Posted: Fri Oct 14, 2005 7:34 am |
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Thank you for taking the time to test my code.
I can change back to channel 0 and it stops working on all three of my 877A chips. I'm going to just use the other channels for now.
| PCM programmer wrote: | I took your code and compiled it with PCM 3.206, and ran it on
a 16F877A on a PicDem2-Plus board. I did change the output pins
from the ones you're using, back to the LED pins of B0, B1, B2, and B3.
Then as I turn the trimpot on the board, the LEDs progressively turn on,
and then as I turn it the other way they progressively turn off.
So it works for me.
Maybe you accidently damaged pin A0 ? |
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Guest
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| Posted: Mon Oct 17, 2005 9:24 pm |
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Can you please post your setup? I'm trying to learn how to use the ADC, but it is not working for me. I am basically pulling up AN1 to VCC using a 1k resistor (datasheet recomends less than 2.5k) but it doesn't work. Here is my code:
Thanks for your help in advance
#include <16F874A.h>
#include <stdlib.h>
#fuses HS,NOWDT,NOPROTECT,NOLVP
#use delay(clock=10000000)
int k;
int16 source1;
long source2;
void main() {
set_tris_d(0x00); //set port d as outputs
setup_adc_ports(ALL_ANALOG);
setup_adc(ADC_CLOCK_INTERNAL); //recommended for a 10 MHz signal
setup_psp(PSP_DISABLED);
setup_spi(FALSE);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
delay_ms(100);
set_adc_channel(1);
delay_ms(100);
source1 = read_adc();
delay_ms(1000);
if(source1 >= 512){
delay_ms(100);
for(k=0; k<5; k++){
output_high(PIN_D2);
delay_ms(1000);
output_low(PIN_D2);
delay_ms(1000);
}
}
} |
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