static void FA_NORETURN( reboot ) ( void )
{
cli() ; // Disable interrupts
USBCON = _B0(USBE) | _B1(FRZCLK) ; // Kill USB
for ( ;; ) // Wait for watchdog to bite (.5s)
;
}
// returns the battery voltage in 10mV units
// for instance: get_battery_voltage() returning 278 equals a voltage of 2.78V
uint16_t get_battery_voltage(void)
{
power_adc_enable();
ADMUX = _B0(REFS1) | _B1(REFS0) // AVCC with external capacitor at AREF pin
#ifndef PREC_BATT_VOLTAGE
| _BV(ADLAR) // left adjust ADC - drops the two LSBs
#endif
| 0b11110; // measure 1.1v internal reference
ADCSRA = _BV(ADEN) // enable ADC
| _BV(ADPS2) | _BV(ADPS1) | _BV(ADPS0) // prescaler 128
| _BV(ADSC); // start conversion
// wait for the conversion to finish
loop_until_bit_is_set(ADCSRA, ADIF);
// remember the result
#ifdef PREC_BATT_VOLTAGE
uint16_t adc_result = ADC;
#else
uint8_t adc_result = ADCH;
#endif
// clear the ADIF bit by writing one
SetBit(ADCSRA, ADIF);
ADCSRA = 0; // disable ADC
power_adc_disable(); // ADC power off
#ifdef PREC_BATT_VOLTAGE
return 112640 / adc_result;
#else
return 28050 / adc_result;
#endif
}
