feat: Add external clock tick handler to reset sequencer or register tick based on clock source.

firmware/Rhythm/Rhythm.ino

@@ -251,6 +251,23 @@ void ProcessSequencerTick(uint32_t tick) {
   }
 }
 
+void HandleExtClockTick() {
+  switch (selected_source) {
+  case Clock::SOURCE_INTERNAL:
+  case Clock::SOURCE_EXTERNAL_MIDI:
+    // Use EXT as Reset when not used for clock source.
+    for (int i = 0; i < 6; i++) {
+      gravity.outputs[i].Low();
+    }
+    gravity.clock.Reset();
+    current_step = 0;
+    break;
+  default:
+    // Register EXT clock tick.
+    gravity.clock.Tick();
+  }
+}
+
 void OnPlayPress() {
   if (!gravity.clock.IsPaused()) {
     gravity.clock.Stop();
@@ -604,6 +621,7 @@ void setup() {
   gravity.encoder.AttachPressRotateHandler(OnEncoderPressRotate);
 
   gravity.clock.AttachIntHandler(ProcessSequencerTick);
+  gravity.clock.AttachExtHandler(HandleExtClockTick);
   // Default to 120 BPM internal
   gravity.clock.SetTempo(120);
   gravity.clock.SetSource(Clock::SOURCE_INTERNAL);