Add documentation to music.c and minor fix to MLDY_PAUSE

firmware/lib/music.c

@@ -12,15 +12,20 @@ static void tune(void) {
 
 void set_note(uint16_t note, uint8_t octave) {
 	if(note != NOTE_PAUSE) {
+		// bring buzzer to a state where inverting it creates sound
 		buzzer_up();
+		// start timer with doubled frequency of tone we want to play
 		start_timer(PRESCALE_8, note >> octave, tune);
 	} else {
+		// do nothing when paused
 		stop_note();
 	}
 }
 
 void stop_note(void) {
+	// turn buzzer off to save energy
 	buzzer_off();
+	// we do not need the timer anymore
 	stop_timer();
 }
 
@@ -32,20 +37,25 @@ void play_melody(uint16_t notes[], size_t len, uint8_t octave, int speed) {
 
 	for(i = 0; i < len; ++i) {
 		if(notes[i] == MLDY_PAUSE) {
+			// user defined pause
 			++i;
-			wait_ms(notes[i] * 4 / length);
+			wait_ms(notes[i]);
 		} else if(notes[i] == MLDY_LENGTH) {
+			// sets length for next tone
 			++i;
 			length = notes[i];
 		} else {
+			// play note
 			set_note(notes[i], octave);
 			test_stop_app();
 			wait_ms(speed * 4 / length);
 
+			// pause after note
 			stop_note();
 			test_stop_app();
 			wait_ms(pause);
 
+			// reset length for next note
 			length = 4;
 		}
 	}