Analog to Digital Conversion in PIC18F4520

meijunfun · Apr 19, 2009

HI,
I need help in my programming. I am using accelerometer which gives analog signal. I need to convert this signal into digital in order for my microcontroller to read. I am having trouble in my programming part, not sure to write the conversion part.

this is the example of my programming:

#include<p18f4520.h>
#include<delays.h>

void main(){
int t;
ADCON0 = 0b00000001;//READ ANALOG VOLTAGE FROM RA0
ADCON1 = 0b00001110;//CONFIGURE ADC, RA0
ADCON2 = 0b10000001;
TRISA = 0b00000001;// RA0 INPUT

while(1){

Delay10TCYx(12);
ADCON0bits.GO = 1;
while(ADCON0bits.DONE);
t=ADRESH+256;

if(t>255){

int x=t;
}
}
}

Is there anything wrong with my programming?

Thanks

Pommie · Apr 19, 2009

You have the result right justified and only read ADRESH so you will only get 2 bits of information. You also add 256 to it and test if greater than 255!

Try changing it to,

Code:

void main(){
int t;
    ADCON0 = 0b00000001;//READ ANALOG VOLTAGE FROM RA0
    ADCON1 = 0b00001110;//CONFIGURE ADC, RA0
    ADCON2 = 0b[COLOR="Red"]0[/COLOR]0000001;
    TRISA = 0b00000001;// RA0 INPUT

    while(1){

        Delay10TCYx(12);
        ADCON0bits.GO = 1;
        while(ADCON0bits.DONE);
        t=ADRESH[COLOR="red"]*256+ADRESL[/COLOR];

        if(t>255){

            int x=t;
        }
    }
}

Your variable will now contain 0 to 1023.

Mike.

meijunfun · Apr 20, 2009

thanks for the help. =D

Analog to Digital Conversion in PIC18F4520

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Pommie

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