// A/D converter routine header



#include "877reg.h"



/* adc initialization: 

	ADCON1 = 0x00; // port A all analog, result left justified

	ADCON0 = 0x81; // 0b 1000 0001 activate A/D, ch 0, Tad = Fosc/32

*/



// inits ADC to configuration x

#define adc_init(x) (ADCON1 = x)



//

// Have to initialize ADC before using this function!!!

//

char adc_read(char ch) {



	ADCON0 = (ch << 3) & 56; // shift ch to correct bit position

	ADCON0 |= 0x81; // Tad = Fosc/32, ADC on.



	delay_us(12); // wait for Tacq

    

    ADCON0 |= 4; // acquire go!

	

    while (ADCON0 & 4); // wait for AD to complete



    delay_us(4); // wait for 2Tad

    

    return ADRESH; // return captured value

}