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peterl
Joined: 09 Oct 2009
Posts: 13
Location: SF,BG
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| 18F2525 ADC problem |
 Posted: Mon Jun 07, 2010 5:02 am |
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Hi guys,
I am trying to do ADC with this microcontroller: 18F2525 and my code:
| Code: |
#include <18F2525.h>
#device adc=10
#FUSES NOWDT //No Watch Dog Timer
#FUSES WDT128 //Watch Dog Timer uses 1:128 Postscale
#FUSES INTRC_IO //Internal RC Osc, no CLKOUT
#FUSES NOPROTECT //Code not protected from reading
#FUSES IESO //Internal External Switch Over mode enabled
#FUSES NOBROWNOUT //No brownout reset
#FUSES BORV20 //Brownout reset at 2.0V
#FUSES NOPUT //No Power Up Timer
#FUSES NOCPD //No EE protection
#FUSES STVREN //Stack full/underflow will cause reset
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOWRT //Program memory not write protected
#FUSES NOWRTD //Data EEPROM not write protected
#FUSES NOEBTR //Memory not protected from table reads
#FUSES NOCPB //No Boot Block code protection
#FUSES NOEBTRB //Boot block not protected from table reads
#FUSES NOWRTC //configuration not registers write protected
#FUSES NOWRTB //Boot block not write protected
#FUSES FCMEN //Fail-safe clock monitor enabled
#FUSES NOXINST //Extended set extension and Indexed Addressing mode disabled (Legacy mode)
#FUSES PBADEN //PORTB pins are configured as analog input channels on RESET
#FUSES LPT1OSC //Timer1 configured for low-power operation
#FUSES MCLR //Master Clear pin enabled
#use delay(clock=4000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
#include "D:\.......\Fuel\main.h"
void main()
{
float adc_values;
setup_adc(ADC_CLOCK_DIV_4);
setup_adc_ports(AN0|VSS_VDD);
set_adc_channel(AN0);
setup_spi(SPI_SS_DISABLED);
setup_wdt(WDT_OFF);
setup_timer_0(RTCC_INTERNAL);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);
for(;;)
{
adc_values=read_adc();
printf("\f%3.0f",adc_values);
delay_ms(300);
}
}
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The problem is that "adc value" is not correct. I use AN0 (PIN 2). When I change voltage on AN0, adc value not change and adc value stay ~30. When I touch with my finger other ANALOG PORTS the value rise up at >700~800, but when I power others ANALOG PORTS value is again ~30. I made everything what I know.
Sorry for my bad english.
Thanks |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jun 07, 2010 11:21 am |
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Try a more simple program that will display ADC values from 0 to 1023
based on the input voltage. Also, make sure you have a ground
connection between the device that supplies the ADC input voltage and
the PIC board's ground. You can't just have the input signal wire to
pin A0. There must also be a ground wire between the two devices,
connected to the ground on each device (or board).
| Code: |
#include <18F2525.h>
#device adc=10
#fuses INTRC_IO, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
//============================
void main()
{
int16 adc_value;
setup_adc_ports(AN0);
setup_adc(ADC_CLOCK_DIV_4);
set_adc_channel(0);
delay_us(20);
while(1)
{
adc_value = read_adc();
printf("%lu", adc_value);
delay_ms(500);
}
} |
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peterl
Joined: 09 Oct 2009
Posts: 13
Location: SF,BG
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| re: PIC18F2525 ADC |
| Posted: Tue Jun 08, 2010 1:12 am |
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The problem was here:
set_adc_channel(AN0); is not correct, correct is set_adc_channel(0);
10X  |
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