xmega_e_temperature_sensor.c

// The XMEGA E-series is different from all the other chips in the line, specifically the temperature sensor.
// It needs to be read in signed mode with a 125kHz clock. Everything else is the same.

void init(void)
{
	// Configure signed conversions, internal 1V VREF, and enable temperature readings
	ADCA.REFCTRL = ADC_CONMODE_bm | ADC_REFSEL_INT1V_gc | ADC_TEMPREF_bm;
	// 12bit resolution in high current mode
	ADCA.CTRLB = ADC_RESOLUTION_12BIT_gc | ADC_CURRLIMIT_HIGH_gc;
	// ADC clock must be 125kHz, 32MHz / 256 = 125kHz
	ADCA.PRESCALER = ADC_PRESCALER_DIV256_gc;
	// 1:1 gain with internal positive reading
	ADCA.CH0.CTRL = ADC_CH_GAIN_1X_gc | ADC_CH_INPUTMODE_INTERNAL_gc;
	// Configure mux to read from temperature sensor
	ADCA.CH0.MUXCTRL = ADC_CH_MUXINT_TEMP_gc;
	// Enable ADC
	ADCA.CTRLA |= ADC_ENABLE_bm;
	// Enable interrupts globally
	sei();
	// Initiate a dummy reading
	ADCA.CH0.CTRL |= ADC_CH_START_bm;
	// Wait for result to be converted
	while(!(ADCA.INTFLAGS & ADC_CH0IF_bm));
	// Clear interrupt bit
	ADCA.INTFLAGS = ADC_CH0IF_bm;
}

uint16_t get_temp(void)
{
	// Initiate reading
	ADCA.CH0.CTRL |= ADC_CH_START_bm;
	// Wait for result to be converted
	while(!(ADCA.INTFLAGS & ADC_CH0IF_bm));
	// Return result
	return ADCA.CH0.RES;
}