usb: add support for midi

src/machine/usb/midi/midi.go

@@ -0,0 +1,79 @@
+package midi
+
+import (
+	"machine"
+)
+
+const (
+	midiEndpointOut = 5 // from PC
+	midiEndpointIn  = 6 // to PC
+)
+
+var Midi *midi
+
+type midi struct {
+	buf            *RingBuffer
+	callbackFuncRx func([]byte)
+	waitTxc        bool
+}
+
+func init() {
+	if Midi == nil {
+		Midi = newMidi()
+	}
+}
+
+// New returns hid-mouse.
+func New() *midi {
+	return Midi
+}
+
+func newMidi() *midi {
+	m := &midi{
+		buf: NewRingBuffer(),
+	}
+	machine.EnableMIDI(m.Callback, m.CallbackRx, nil)
+	return m
+}
+
+func (m *midi) SetCallback(callbackRx func([]byte)) {
+	m.callbackFuncRx = callbackRx
+}
+
+func (m *midi) Write(b []byte) (n int, err error) {
+	i := 0
+	for i = 0; i < len(b); i += 4 {
+		m.tx(b[i : i+4])
+	}
+	return i, nil
+}
+
+// sendUSBPacket sends a MIDIPacket.
+func (m *midi) sendUSBPacket(b []byte) {
+	machine.SendUSBInPacket(midiEndpointIn, b)
+}
+
+// from BulkIn
+func (m *midi) Callback() {
+	m.waitTxc = false
+	if b, ok := m.buf.Get(); ok {
+		m.waitTxc = true
+		m.sendUSBPacket(b)
+	}
+}
+
+func (m *midi) tx(b []byte) {
+	if m.waitTxc {
+		m.buf.Put(b)
+	} else {
+		m.waitTxc = true
+		m.sendUSBPacket(b)
+	}
+}
+
+// from BulkOut
+func (m *midi) CallbackRx(b []byte) {
+	if m.callbackFuncRx != nil {
+		m.callbackFuncRx(b)
+	}
+}