diff options
Diffstat (limited to 'main.c')
| -rw-r--r-- | main.c | 44 |
1 files changed, 36 insertions, 8 deletions
@@ -33,6 +33,35 @@ #define PWM_MAX 2500 #define PWM_TOP 20000 +#define VCC_MIN 4900 + +#define LED_PIN PB5 +#define LED_DDR DDRB +#define LED_PORT PORTB + +/* Measure vcc by measuring known internal 1.1v bandgap + * reference voltage against AVCC. + */ +uint16_t getvcc(void) +{ + uint16_t vcc; + + ADMUX |= (1 << REFS0); + ADMUX |= (1 << MUX3) | (1 << MUX2) | (1 << MUX1); + ADCSRA |= (1 << ADEN) | (1 << ADPS2) | (1 << ADPS0); + + // https://www.sciencetronics.com/greenphotons/?p=1521 + _delay_us(500); + + ADCSRA |= (1 << ADSC); + while (ADCSRA & (1 << ADSC)) + ; + vcc = (1100UL * 1023 / ADC); + + ADCSRA &= ~(1 << ADEN); + return vcc; +} + int main(void) { /* disable watchdog timer */ @@ -42,6 +71,10 @@ int main(void) WDTCSR |= (1 << WDCE) | (1 << WDE); WDTCSR = 0x00; + /* battery check */ + LED_DDR |= (1 << LED_PIN); + LED_PORT &= ~(1 << LED_PIN); + /* init input ports */ INPUT_DDR &= ~((1 << BACK_LOCK_PIN) | (1 << BACK_UNLOCK_PIN) | (1 << FRONT_LOCK_PIN) | (1 << FRONT_UNLOCK_PIN) | @@ -69,6 +102,9 @@ int main(void) sei(); for (;;) { + if (getvcc() < VCC_MIN) + LED_PORT |= (1 << LED_PIN); + sleep_bod_disable(); set_sleep_mode(SLEEP_MODE_PWR_DOWN); sleep_mode(); @@ -102,24 +138,18 @@ static inline int is_pressed(uint8_t btn) ISR(FPM_INT_VEC) { - cli(); - if (fpm_match()) { unlock(); fpm_led(BREATHE, BLUE, 1); } else { fpm_led(BREATHE, RED, 1); } - - sei(); } ISR(BTN_INT_VEC) { uint16_t id; - cli(); - if (is_pressed(FRONT_LOCK_PIN)) { lock(); fpm_led(FLASH, RED, 1); @@ -137,6 +167,4 @@ ISR(BTN_INT_VEC) } else fpm_led(BREATHE, RED, 1); } - - sei(); } |