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RoMar
Joined: 22 May 2020
Posts: 6
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| pic18F26K22 ADC 10-bit resolution!? |
 Posted: Sun Aug 16, 2020 1:23 pm |
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Hi,
I'm using ccs (5.008 version) to program a pic18F26K22.
I need to use an ADC. In datasheet I can see this PIC has a ADC with 10-bit.
With this ADC, I want to read voltage's values from 1 to 5Volts with voltage divider circuit.
The resolution is 0-1024 (Full-Scale Range).
But with the code below I just have values from 1 to 255, this means just 8-bit wide!!?
At value's ADC 255 corresponds to 1,23 Volts. And when the voltage is greater than 1.23V,
the ADC gives again a lower values, ( lower than 255 ) something is missing here
(some values are in the table below).
I think I'm doing right. I tried many ways to get 10-bit resolution, but I just have 8-bits??!
The CCS code is below. I can't understand what is missing here, please I need some help.
__U___|__ADC(bit)_|_ U_adc__ [adc U_float]__multimeter
0.494V__|____ 104___|_ 49___|___0.4929___|__0.50V
0.494V__|____ 104___|_ 49___|___0.4929___|__0.50V
0.494V__|____ 104___|_ 49___|___0.4929___|__0.50V
0.618V__|____ 130___|_ 61___|___0.6162___|__0.63V
0.782V__|____ 166___|_ 78___|___0.7868___|__0.80V
1.146V__|____ 242___|_ 114 _|___1.1470___|__1.16V
1.206V__|____ 255___|_ 120__|___1.2087___|__1.23V
0.120V__|____ 26____|_ 12___|___0.1232___|__1.38V ---->X
0.120V__|____ 27____|_ 12___|___0.1279___|__1.38V ---->X
0.120V__|____ 27____|_ 12___|___0.1279___|__1.38V ---->X
0.284V__|____ 61____|_ 28___|___0.2891___|__1.54V ---->X
0.284V__|____ 61____|_ 28___|___0.2891___|__1.54V ---->X
0.284V__|____ 61____|_ 28___|___0.2891___|__1.54V ---->X
| Code: |
#include <18F26K22.h>
#fuses HSH, PLLEN, NOLVP, NOPROTECT, NOWDT, NOXINST
#device ADC=10
#use delay(crystal=12MHz, clock=48MHZ) //cristal de 12MHz
#use rs232(stream=UART_1,baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
#include "lcd.c"
void tabela(void);
int main(){
unsigned int8 value_ADC, adcU;
float adcUFloat;
char valorU[6]=" V";
lcd_init();
delay_ms(500);
setup_adc_ports( sAN0 | VSS_VDD );
setup_adc(ADC_CLOCK_DIV_16);
delay_ms(5000);
tabela();
for(;;){
delay_ms(500);
set_adc_channel(0);
delay_ms(1);
value_ADC = read_adc();
delay_ms(500);
adcU = value_ADC*0.474;
adcUFloat = value_ADC*0.00474;
valorU[0] = adcU/100%10+48;
valorU[1] = ".";
valorU[2] = adcU/10%10+48;
valorU[3] = adcU%10+48;
valorU[4] = adcU*10%10+48;
printf("\t %c",valorU[0]);
printf("%c",valorU[1]);
printf("%c",valorU[2]);
printf("%c",valorU[3]);
printf("%c",valorU[4]);
printf("%c",valorU[5]);
printf("\t |\t %u ", value_ADC);
printf("\t |\t %u ", adcU);
printf("\t |\t %0.4f \r\n", adcUFloat);
lcd_gotoxy( 5, 1);
printf(lcd_putc, valorU);
lcd_gotoxy( 11, 1);
printf(lcd_putc, " .....");
delay_ms(5000);
}
return 0;
}
void tabela(){
lcd_gotoxy(1, 1);
printf(lcd_putc, " ");
lcd_gotoxy(2, 1);
printf(lcd_putc, "U= ");
printf("\r\n");
printf("\t U");
printf("\t ADC(bit) ");
printf("\t U_adc ");
printf("\t adc U_float \r\n");
}
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Best Regards[/list] |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Re: pic18F26K22 ADC 10-bit resolution!? |
| Posted: Sun Aug 16, 2020 1:34 pm |
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Look closely at this and you'll see what's wrong:
| RoMar wrote: |
unsigned int8 value_ADC, adcU;
value_ADC = read_adc();
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RoMar
Joined: 22 May 2020
Posts: 6
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| Posted: Sun Aug 16, 2020 2:10 pm |
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In first place, thanks for your time and help,
Of course,
int8 -> 0 - 255
I change to int16 -> 0 to 65535
and
printf("\t |\t %Lu ", value_ADC);
printf("\t |\t %Lu ", adcU);
and everything is working,
well, I'm new here, thus mistakes are very close to me yet.
Thanks a lot. |
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