zoom/firmware/adc.c

#include "config.h"
#include "adc.h"
#include "timer.h"

/* Currently using software SPI because it's easy.
   Consider using hardware SPI with DMA on a timer, though. */

#define TRIS_SDATA TRISFbits.TRISF7
#define R_SDATA PORTFbits.RF7
#define TRIS_SCLK TRISFbits.TRISF6
#define LAT_SCLK LATFbits.LATF6
#define TRIS_CS TRISBbits.TRISB2
#define LAT_CS LATBbits.LATB2

void adc_init(void)
{
	TRIS_SDATA = 1;
	LAT_CS = IO_HIGH;
	TRIS_CS = 0;
	LAT_SCLK = IO_HIGH;
	TRIS_SCLK = 0;
}

int16_t adc_get(void)
{
	uint16_t v = 0;
	int i;

	LAT_CS = IO_LOW;
	for (i = 0; i < 16; i++) {
		v <<= 1;
		if (R_SDATA == IO_HIGH)
			v |= 1;
		LAT_SCLK = IO_LOW;
		nop(); nop(); nop();
		LAT_SCLK = IO_HIGH;
	}
	LAT_CS = IO_HIGH;

	/* Sign-extend the 12-bit value */
	if (v & 0x0800)
		v |= 0xF000;
	else
		v &= ~0xF000;
	return (int16_t) v;
}

uint16_t adc_get_raw(void)
{
	uint16_t v = 0;
	int i;

	LAT_CS = IO_LOW;
	for (i = 0; i < 16; i++) {
		v <<= 1;
		if (R_SDATA == IO_HIGH)
			v |= 1;
		LAT_SCLK = IO_LOW;
		nop(); nop(); nop();
		LAT_SCLK = IO_HIGH;
	}
	LAT_CS = IO_HIGH;

	return (uint16_t) v;
}