webradio/firmware/batmon.c

#include <avr/io.h>
#include "batmon.h"
#include "systick.h"

static uint8_t vbat = 0;

void batmon_init()
{
	TCCR0A = 0;
	TCCR0B = (1 << CS02);
	TIMSK0 = (1 << TOIE0);

	ADCSRA = (1 << ADPS2) | (1 << ADPS1); // 125 kHz ADC clock
	ADMUX = ADC_CHANNEL | (1 << REFS0) | (1 << REFS1) | (1 << ADLAR); // Internal 1.2V bandgap, left adj.
	ADCSRB = 0;
#if ADC_CHANNEL < 7
	DIDR0 = (1 << ADC_CHANNEL); // Disconnect digital channel
#endif

	// Enable voltage divider
	PORT_ADCC(DDR) |= PIN_ADCC;
	PORT_ADCC(PORT) &= ~PIN_ADCC;

	// Enable ADC
	ADCSRA |= (1 << ADEN);
	ADCSRA |= (1 << ADSC);
}

uint8_t batmon_proc()
{
	static uint16_t sum = 0;
	static uint8_t cnt = 0;

	if (ADCSRA & (1 << ADIF)) {
		sum += ADCH;
		if (!(++cnt)) {
			vbat = sum >> 8;
			sum = 0;
			if (vbat < BAT_THRES_POWER_OFF)
				return 1;
		}
		ADCSRA &= ~(1 << ADIF);
		ADCSRA |= (1 << ADSC); // TODO: I want this to work off TIMER0
	}
	return 0;
}

inline uint8_t batmon_get_voltage()
{
	return vbat;
}

static uint8_t batmon_get_voltage_sync()
{
	uint16_t sum = 0;
	uint8_t cnt = 255;

	ADCSRA |= (1 << ADSC);

	do {
		if (ADCSRA & (1 << ADIF)) {
			sum += ADCH;
			ADCSRA &= ~(1 << ADIF);
			ADCSRA |= (1 << ADSC);
			cnt--;
		}
	} while (cnt);

	return (sum >> 8);
}

// Note: Call batmon_init() after using this function before using batmon_proc() again
inline uint8_t batmon_ok_to_boot()
{
	return (batmon_get_voltage_sync() > BAT_THRES_POWER_ON);
}