Define function to measure battery level.

1 files changed, 23 insertions, 1 deletions

diff --git a/main.c b/main.c
index beeb87a..a16101d 100644
--- a/main.c
+++ b/main.c
@@ -100,6 +100,28 @@ static inline void flash_led(void)
 	}
 }
 
+static inline uint16_t get_bat_volt(void)
+{
+	uint16_t vbg;
+
+	ADMUX |= (1 << REFS0);
+	ADCSRA |= (1 << ADEN) | (1 << ADPS2) | (1 << ADPS1); /* clk: 50-200 kHz */
+
+	// https://www.sciencetronics.com/greenphotons/?p=1521
+	_delay_us(500);
+
+	ADCSRA |= (1 << ADSC);
+	while (ADCSRA & (1 << ADSC))
+		; 
+
+	ADCSRA &= ~(1 << ADEN);
+	vbg = 3300UL / 1024 * ADC
+
+	ADCSRA &= ~(1 << ADEN);
+
+	return vbg * 3;
+}
+
 int main(void)
 {
 	uint16_t id;
@@ -124,7 +146,7 @@ int main(void)
 	TCCR1A |= (1 << COM1A1);
 	SERVO_DDR |= (1 << SERVO_PIN);
 
-	/* battery check */
+	/* bat check */
 	LED_DDR |= (1 << LED_PIN);
 	LED_PORT &= ~(1 << LED_PIN);