Added 2 examples for teensy as USB MIDI clock slave and master

examples/TeensyUsbMasterMidiClock/TeensyUsbMasterMidiClock.ino

@@ -0,0 +1,76 @@
+/* USB MIDI Sync Box
+ *  
+ * This example demonstrates how to change the USB MIDI 
+ * device name on Teensy LC and 3.x.  When creating more
+ * that one MIDI device, custom names are much easier to
+ * use when selecting each device in MIDI software on
+ * your PC or Mac.  The custom name is in the "name.c" tab.
+ *
+ * Windows and Macintosh systems often cache USB info.
+ * After changing the name, you may need to test on a
+ * different computer to observe the new name, or take
+ * steps to get your operating system to "forget" the
+ * cached info.  (TODO: wanted... can anyone contribute
+ * instructions for these systems)
+ * 
+ * You must select MIDI from the "Tools > USB Type" menu
+ * 
+ * This example code is in the public domain.
+ */
+
+#include <uClock.h>
+
+uint8_t bpm_blink_timer = 1;
+void handle_bpm_led(uint32_t * tick)
+{
+  // BPM led indicator
+  if ( !(*tick % (96)) || (*tick == 1) ) {  // first compass step will flash longer
+    bpm_blink_timer = 8;
+    digitalWrite(LED_BUILTIN, HIGH);
+  } else if ( !(*tick % (24)) ) {   // each quarter led on
+    digitalWrite(LED_BUILTIN, HIGH);
+  } else if ( !(*tick % bpm_blink_timer) ) { // get led off
+    digitalWrite(LED_BUILTIN, LOW);
+    bpm_blink_timer = 1;
+  }
+}
+
+// Internal clock handlers
+void ClockOut96PPQN(uint32_t * tick) {
+  // Send MIDI_CLOCK to external gears
+  usbMIDI.sendRealTime(usbMIDI.Clock);
+  handle_bpm_led(tick);
+}
+
+void onClockStart() {
+  usbMIDI.sendRealTime(usbMIDI.Start);
+}
+
+void onClockStop() {
+  usbMIDI.sendRealTime(usbMIDI.Stop);
+}
+
+void setup() {
+  // A led to count bpms
+  pinMode(LED_BUILTIN, OUTPUT);
+  
+  // Setup our clock system
+  // drift for USB Teensy
+  uClock.setDrift(1);
+  // Inits the clock
+  uClock.init();
+  // Set the callback function for the clock output to send MIDI Sync message.
+  uClock.setClock96PPQNOutput(ClockOut96PPQN);
+  // Set the callback function for MIDI Start and Stop messages.
+  uClock.setOnClockStartOutput(onClockStart);  
+  uClock.setOnClockStopOutput(onClockStop);
+  // Set the clock BPM to 126 BPM
+  uClock.setTempo(126);
+  // Starts the clock, tick-tac-tick-tac...
+  uClock.start();
+}
+
+// Do it whatever to interface with Clock.stop(), Clock.start(), Clock.setTempo() and integrate your environment...
+void loop() {
+
+}

examples/TeensyUsbSlaveMidiClock/TeensyUsbSlaveMidiClock.ino

@@ -0,0 +1,95 @@
+/* USB MIDI Sync Slave Box
+ *  
+ * This example demonstrates how to change the USB MIDI 
+ * device name on Teensy LC and 3.x.  When creating more
+ * that one MIDI device, custom names are much easier to
+ * use when selecting each device in MIDI software on
+ * your PC or Mac.  The custom name is in the "name.c" tab.
+ *
+ * Windows and Macintosh systems often cache USB info.
+ * After changing the name, you may need to test on a
+ * different computer to observe the new name, or take
+ * steps to get your operating system to "forget" the
+ * cached info.  (TODO: wanted... can anyone contribute
+ * instructions for these systems)
+ * 
+ * You must select MIDI from the "Tools > USB Type" menu
+ * 
+ * This example code is in the public domain.
+ */
+
+#include <uClock.h>
+
+uint8_t bpm_blink_timer = 1;
+void handle_bpm_led(uint32_t * tick)
+{
+  // BPM led indicator
+  if ( !(*tick % (96)) || (*tick == 1) ) {  // first compass step will flash longer
+    bpm_blink_timer = 8;
+    digitalWrite(LED_BUILTIN, HIGH);
+  } else if ( !(*tick % (24)) ) {   // each quarter led on
+    digitalWrite(LED_BUILTIN, HIGH);
+  } else if ( !(*tick % bpm_blink_timer) ) { // get led off
+    digitalWrite(LED_BUILTIN, LOW);
+    bpm_blink_timer = 1;
+  }
+}
+
+// Internal clock handlers
+void ClockOut96PPQN(uint32_t * tick) {
+  // Send MIDI_CLOCK to external gears on other port?
+  //usbMIDI.sendRealTime(usbMIDI.Clock);
+  handle_bpm_led(tick);
+}
+
+void onClockStart() {
+  //usbMIDI.sendRealTime(usbMIDI.Start);
+}
+
+void onClockStop() {
+  //usbMIDI.sendRealTime(usbMIDI.Stop);
+}
+
+// External clock handlers
+void onExternalClock()
+{
+  uClock.clockMe();
+}
+
+void onExternalStart()
+{
+  uClock.start();
+}
+
+void onExternalStop()
+{
+  uClock.stop();
+}
+
+void setup() {
+  // A led to count bpms
+  pinMode(LED_BUILTIN, OUTPUT);
+  
+  // Setup realtime midi event handlers
+  usbMIDI.setHandleClock(onExternalClock);
+  usbMIDI.setHandleStart(onExternalStart);
+  usbMIDI.setHandleStop(onExternalStop);
+
+  // Setup our clock system
+  // drift for USB Teensy
+  uClock.setDrift(1);
+  // Inits the clock
+  uClock.init();
+  // Set the callback function for the clock output to send MIDI Sync message.
+  uClock.setClock96PPQNOutput(ClockOut96PPQN);
+  // Set the callback function for MIDI Start and Stop messages.
+  uClock.setOnClockStartOutput(onClockStart);  
+  uClock.setOnClockStopOutput(onClockStop);
+  // set to external sync mode
+  uClock.setMode(1);
+}
+
+void loop() {
+  // Grab all midi data as fast as we can!
+  while (usbMIDI.read()) {}
+}

src/uClock.cpp

@@ -185,7 +185,11 @@ void uClockClass::setTempo(uint16_t bpm)
 uint16_t uClockClass::getTempo() 
 {
 	if (mode == EXTERNAL_CLOCK) {
-		tempo = (156250 / interval);
+		uint16_t external_interval;
+		ATOMIC(
+			external_interval = interval;
+		)
+		tempo = (156250 / external_interval);
 	}
 	return tempo;
 }