A/D reading with 16F877

[pat]

Hi! I built a simple thermometer that reads temperature from 0-50 degree. But problem I got is that the readings I get jump some values. As an example, A/D reads from 0 to 009F, than jumps to 0100. It doesn't read from 00A0 to 00FF. Same from 0100 to 0180, than jumps to 0200; and again from 0200 to 02A0, than jumps to 0300 and finally reads ok to 03FF. Sorry but I just don't understand with it does that. Any ideas?

Thanks a lot.

Here's the code.

void main()
{

int iTemp;
long lTemp;
float fTemp;

setup_adc_ports(A_ANALOG);
setup_adc(ADC_CLOCK_DIV_2);
setup_spi(FALSE);
setup_psp(PSP_DISABLED);
setup_counters(RTCC_INTERNAL,RTCC_DIV_2);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_ccp1(CCP_OFF);
setup_ccp2(CCP_OFF);
lcd_init();

lcd_gotoxy(1,1);
printf(LCD_PUTC, "Bonjour, il fait: ");
lcd_gotoxy(1,2);
printf(LCD_PUTC, "Valeur HEX: ");
lcd_gotoxy(21,1);
printf(LCD_PUTC, "Valeur C: ");

while(1)
{
delay_ms(100);
set_adc_channel(0);
delay_ms(100);
lTemp = Read_ADC();

lcd_gotoxy(12,2);
printf(LCD_PUTC, "\%4LX", lTemp);

fTemp = (lTemp / 20.48);
iTemp = ceil(fTemp);

lcd_gotoxy(30,1);
printf(LCD_PUTC, "\%2u", iTemp);
}
}
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516965

[PCM programmer]

:=void main()
:= {
:=
:= int iTemp;
:= long lTemp;
:= float fTemp;
:=
:= setup_adc_ports(A_ANALOG);

This next line immediately draws my attention. The data sheet
says to use the Fosc/2 clock only if your crystal frequency
is at 1.25 MHz or below. What freq are you using ?

:= setup_adc(ADC_CLOCK_DIV_2);

:= setup_spi(FALSE);
:= setup_psp(PSP_DISABLED);
:= setup_counters(RTCC_INTERNAL,RTCC_DIV_2);
:= setup_timer_1(T1_DISABLED);
:= setup_timer_2(T2_DISABLED,0,1);
:= setup_ccp1(CCP_OFF);
:= setup_ccp2(CCP_OFF);
:= lcd_init();
:=
:= lcd_gotoxy(1,1);
:= printf(LCD_PUTC, "Bonjour, il fait: ");
:= lcd_gotoxy(1,2);
:= printf(LCD_PUTC, "Valeur HEX: ");
:= lcd_gotoxy(21,1);
:= printf(LCD_PUTC, "Valeur C: ");
:=
:= while(1)
:= {
:= delay_ms(100);
:= set_adc_channel(0);
:= delay_ms(100);
:= lTemp = Read_ADC();
:=
:= lcd_gotoxy(12,2);
:= printf(LCD_PUTC, "\%4LX", lTemp);
:=
:= fTemp = (lTemp / 20.48);
:= iTemp = ceil(fTemp);
:=
:= lcd_gotoxy(30,1);
:= printf(LCD_PUTC, "\%2u", iTemp);
:= }
:= }
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516966

[pat]

Oups, actually I'm using a 20MHz crystal.

Pat
:=:=void main()
:=:= {
:=:=
:=:= int iTemp;
:=:= long lTemp;
:=:= float fTemp;
:=:=
:=:= setup_adc_ports(A_ANALOG);
:=
:=This next line immediately draws my attention. The data sheet
:=says to use the Fosc/2 clock only if your crystal frequency
:=is at 1.25 MHz or below. What freq are you using ?
:=
:=:= setup_adc(ADC_CLOCK_DIV_2);
:=
:=:= setup_spi(FALSE);
:=:= setup_psp(PSP_DISABLED);
:=:= setup_counters(RTCC_INTERNAL,RTCC_DIV_2);
:=:= setup_timer_1(T1_DISABLED);
:=:= setup_timer_2(T2_DISABLED,0,1);
:=:= setup_ccp1(CCP_OFF);
:=:= setup_ccp2(CCP_OFF);
:=:= lcd_init();
:=:=
:=:= lcd_gotoxy(1,1);
:=:= printf(LCD_PUTC, "Bonjour, il fait: ");
:=:= lcd_gotoxy(1,2);
:=:= printf(LCD_PUTC, "Valeur HEX: ");
:=:= lcd_gotoxy(21,1);
:=:= printf(LCD_PUTC, "Valeur C: ");
:=:=
:=:= while(1)
:=:= {
:=:= delay_ms(100);
:=:= set_adc_channel(0);
:=:= delay_ms(100);
:=:= lTemp = Read_ADC();
:=:=
:=:= lcd_gotoxy(12,2);
:=:= printf(LCD_PUTC, "\%4LX", lTemp);
:=:=
:=:= fTemp = (lTemp / 20.48);
:=:= iTemp = ceil(fTemp);
:=:=
:=:= lcd_gotoxy(30,1);
:=:= printf(LCD_PUTC, "\%2u", iTemp);
:=:= }
:=:= }
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516967

[PCM programmer]

:=Oups, actually I'm using a 20MHz crystal.
-------------------------------------------------------

Change it to this:

setup_adc(ADC_CLOCK_DIV_32);
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516968

[pat]

Yesss! You're the man!
Thanks again for that!

Pat

:=:=Oups, actually I'm using a 20MHz crystal.
:=-------------------------------------------------------
:=
:=Change it to this:
:=
:=setup_adc(ADC_CLOCK_DIV_32);
___________________________
This message was ported from CCS's old forum
Original Post ID: 144516987