Add MIDIUSB.h for Arduino compatibility

keywords.txt

 AfterTouchChannel	LITERAL1
 PitchBend	LITERAL1
 SystemExclusive	LITERAL1
+midiEventPacket_t	LITERAL1
+MidiUSB	KEYWORD1
+sendMIDI	KEYWORD2
 
 # USB RawHID
 RawHID	KEYWORD1

teensy3/MIDIUSB.h

+#ifndef MIDIUSB_h
+#define MIDIUSB_h
+
+// For compatibility with Arduino's MIDIUSB library
+
+#include "usb_midi.h"
+
+#ifdef __cplusplus
+#ifndef MIDI_INTERFACE
+#error "Please select MIDI in Tools > USB Type to use MIDIUSB.h"
+#endif
+
+typedef struct {
+ union {
+  struct {
+	uint8_t header;
+	uint8_t byte1;
+	uint8_t byte2;
+	uint8_t byte3;
+  };
+	uint32_t word;
+ };
+} midiEventPacket_t;
+
+
+class MIDI_
+{
+public:
+	constexpr MIDI_(void) { }
+	uint32_t available(void) {
+		return usb_midi_available();
+	}
+	midiEventPacket_t read(void) {
+		midiEventPacket_t event;
+		event.word = usb_midi_read_message();
+		return event;
+	}
+	void flush(void) {
+		usb_midi_flush_output();
+	}
+	void sendMIDI(midiEventPacket_t event) {
+		usb_midi_write_packed(event.word);
+	}
+	size_t write(const uint8_t *buffer, size_t size) {
+		// TODO - is this really needed?
+		return 0;
+	}
+	operator bool() {
+		// TODO - is this really needed?
+		return true;
+	}
+};
+extern MIDI_ MidiUSB;
+
+#endif // __cplusplus
+#endif // MIDIUSB_h

teensy3/usb_midi.c

 	}
 }
 
+uint32_t usb_midi_available(void)
+{
+	uint32_t index;
+
+	if (!rx_packet) {
+		if (!usb_configuration) return 0;
+		rx_packet = usb_rx(MIDI_RX_ENDPOINT);
+		if (!rx_packet) return 0;
+		if (rx_packet->len == 0) {
+			usb_free(rx_packet);
+			rx_packet = NULL;
+			return 0;
+		}
+	}
+	index = rx_packet->index;
+	return rx_packet->len - index;
+}
+
+uint32_t usb_midi_read_message(void)
+{
+	uint32_t n, index;
+
+	if (!rx_packet) {
+		if (!usb_configuration) return 0;
+		rx_packet = usb_rx(MIDI_RX_ENDPOINT);
+		if (!rx_packet) return 0;
+		if (rx_packet->len == 0) {
+			usb_free(rx_packet);
+			rx_packet = NULL;
+			return 0;
+		}
+	}
+	index = rx_packet->index;
+	n = ((uint32_t *)rx_packet->buf)[index/4];
+	index += 4;
+	if (index < rx_packet->len) {
+		rx_packet->index = index;
+	} else {
+		usb_free(rx_packet);
+		rx_packet = usb_rx(MIDI_RX_ENDPOINT);
+	}
+	return n;
+}
 
 int usb_midi_read(uint32_t channel)
 {

teensy3/usb_midi.h

 void usb_midi_send_sysex(const uint8_t *data, uint32_t length);
 void usb_midi_flush_output(void);
 int usb_midi_read(uint32_t channel);
+uint32_t usb_midi_available(void);
+uint32_t usb_midi_read_message(void);
 extern uint8_t usb_midi_msg_channel;
 extern uint8_t usb_midi_msg_type;
 extern uint8_t usb_midi_msg_data1;