Playing with the ADC on a PIC10F222

gistfile1.c

#include <xc.h>
#include <stdint.h>

#define _XTAL_FREQ  4000000 // required for __delay_ms()
#define DELAY       1000
#define THRESHOLD   100

#pragma config MCLRE=OFF, MCPU=OFF, CP=OFF, WDTE=OFF, IOSCFS=4MHZ

void
blink ()
{
    GPIObits.GP0 = 1;
    __delay_ms(300);
    GPIObits.GP0 = 0;
    __delay_ms(300);
}

int
main (void)
{
    TRISGPIO = 0b00000010; // GP1 input

    // GP1 = analog, GP0 = digital
    ADCON0bits.ANS1 = 1;
    ADCON0bits.ANS0 = 0;

    // select AN1
    ADCON0bits.CHS1 = 0;
    ADCON0bits.CHS0 = 1;

    // turn ADC on
    ADCON0bits.ADON = 1;

    blink();

    for(;;){
        // start conversion
        ADCON0bits.GO = 1;

        // wait until conversion finishes
        while (ADCON0bits.nDONE);

        // read result and set output as necessary
        if(ADRES > THRESHOLD){
            GPIObits.GP0 = 1;
        } else {
            GPIObits.GP0 = 0;
        }

        //blink();
        __delay_ms(DELAY);
    }
}

Nope, simply a case of using the wrong value for the ADC mux. Spotted by @MarkAtMicrohip: "Looks like you have CHS0 and CHS1 backward. You're always looking at the internal voltage reference." 😞