diff --git a/firmware/apps/buggy.c b/firmware/apps/buggy.c
index 080b5ea..d4edfcd 100644
--- a/firmware/apps/buggy.c
+++ b/firmware/apps/buggy.c
@@ -8,14 +8,19 @@
 static void init(void) {
 	pentatonic_direction(ALL_OUT);
 	photons_init();
+
+	led_on(RIGHT);
 }
 
 static void run(void) {
-	uint16_t light = photons_measure();
+	uint8_t light = photons_measure();
 
 	pentatonic_all_led_set(light >> 3);
 
-	wait_ms(500);
+	led_inv(LEFT);
+	led_inv(RIGHT);
+
+	wait_ms(100);
 }
 
 REGISTER(run, init, NULL);
diff --git a/firmware/include/pentabug/hal.h b/firmware/include/pentabug/hal.h
index 6549fc6..dd692fb 100644
--- a/firmware/include/pentabug/hal.h
+++ b/firmware/include/pentabug/hal.h
@@ -34,6 +34,7 @@ void button_reset(uint8_t btn);
 void led_set(uint8_t led, uint8_t state);
 void led_on(uint8_t led);
 void led_off(uint8_t led);
+uint8_t led_state(uint8_t led);
 void led_inv(uint8_t led);
 
 // MOTOR
diff --git a/firmware/include/pentabug/photons.h b/firmware/include/pentabug/photons.h
index b2cd2ce..5f70ce6 100644
--- a/firmware/include/pentabug/photons.h
+++ b/firmware/include/pentabug/photons.h
@@ -5,6 +5,8 @@
 
 void photons_init(void);
 
+void photons_stop(void);
+
 uint8_t photons_measure(void);
 
 #endif /* PHOTONS_H */
diff --git a/firmware/lib/hal.c b/firmware/lib/hal.c
index 4d32d4c..15befcf 100644
--- a/firmware/lib/hal.c
+++ b/firmware/lib/hal.c
@@ -165,6 +165,14 @@ void led_inv(uint8_t led) {
 	}
 }
 
+uint8_t led_state(uint8_t led) {
+	if(led == RIGHT) {
+		return !(PORTC & (1 << 2));
+	} else {
+		return !(PORTD & (1 << 4));
+	}
+}
+
 void motor_set(uint8_t state) {
 	if(state) {
 		motor_on();
diff --git a/firmware/lib/photons.c b/firmware/lib/photons.c
index 20653f0..5d8c506 100644
--- a/firmware/lib/photons.c
+++ b/firmware/lib/photons.c
@@ -9,11 +9,15 @@ void photons_init(void) {
 	ADCSRA |= (1 << ADEN);
 }
 
+void photons_stop(void) {
+	ADCSRA &= ~(1 << ADEN);
+}
+
 uint8_t photons_measure(void) {
 	// save old state
 
-	uint8_t old_port = PORTC;
-	uint8_t old_ddr = DDRC;
+	uint8_t old_right = led_state(RIGHT);
+	uint8_t old_left = led_state(LEFT);
 
 	// all leds off
 
@@ -22,6 +26,7 @@ uint8_t photons_measure(void) {
 
 	// set to ground for discharge
 
+	DDRC |= 1 << 3;
 	PORTC &= ~(1 << 3);
 
 	// wait for discharge
@@ -38,6 +43,7 @@ uint8_t photons_measure(void) {
 
 	// start measurement
 
+	// TODO: why can't i move this to the initialization?
 	ADMUX  = (1 << REFS0) | (1 << ADLAR);
 	ADCSRA |= (1 << ADPS2) | (1 << ADPS1);
 
@@ -51,14 +57,13 @@ uint8_t photons_measure(void) {
 
 	uint8_t res = ADCH;
 
-	// disable adc
-
-	/*ADCSRA &= ~(1 << ADEN);*/
-
 	// restore state
 
-	PORTC = old_port;
-	DDRC = old_ddr;
+	PORTC |= 1 << 3;
+	DDRC |= 1 << 3;
+
+	led_set(RIGHT, old_right);
+	led_set(LEFT, old_left);
 
 	// done