usb: add support for midi

Makefile

@@ -595,11 +595,13 @@ endif
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=feather-m4          examples/pwm
 	@$(MD5SUM) test.hex
-	# test usbhid
+	# test usb
 	$(TINYGO) build -size short -o test.hex -target=feather-nrf52840    examples/hid-keyboard
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=circuitplay-express examples/hid-keyboard
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=feather-nrf52840    examples/usb-midi
+	@$(MD5SUM) test.hex
 ifneq ($(STM32), 0)
 	$(TINYGO) build -size short -o test.hex -target=bluepill            examples/blinky1
 	@$(MD5SUM) test.hex

src/examples/usb-midi/main.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"fmt"
+	"machine"
+	"machine/usb/midi"
+	"time"
+)
+
+func main() {
+	led := machine.LED
+	led.Configure(machine.PinConfig{Mode: machine.PinOutput})
+
+	button := machine.BUTTON
+	button.Configure(machine.PinConfig{Mode: machine.PinInputPullup})
+
+	m := midi.New()
+	m.SetCallback(func(b []byte) {
+		led.Set(!led.Get())
+		fmt.Printf("% X\r\n", b)
+		m.Write(b)
+	})
+
+	prev := true
+	chords := []struct {
+		name string
+		keys []byte
+	}{
+		{name: "C ", keys: []byte{60, 64, 67}},
+		{name: "G ", keys: []byte{55, 59, 62}},
+		{name: "Am", keys: []byte{57, 60, 64}},
+		{name: "F ", keys: []byte{53, 57, 60}},
+	}
+	index := 0
+
+	for {
+		current := button.Get()
+		if prev != current {
+			led.Set(current)
+			if current {
+				for _, c := range chords[index].keys {
+					m.Write([]byte{0x08, 0x80, c, 0x40})
+				}
+				index = (index + 1) % len(chords)
+			} else {
+				for _, c := range chords[index].keys {
+					m.Write([]byte{0x09, 0x90, c, 0x40})
+				}
+			}
+			prev = current
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+}

src/machine/usb.go

@@ -32,6 +32,7 @@ var usbDescriptor = descriptorCDC
 const (
 	usbDescriptorConfigCDC = 1 << iota
 	usbDescriptorConfigHID
+	usbDescriptorConfigMIDI
 )
 
 var usbDescriptorConfig uint8 = usbDescriptorConfigCDC
@@ -137,11 +138,13 @@ const (
 	usb_HID_INTERFACE      = 2 // HID
 
 	// Endpoint
-	usb_CONTROL_ENDPOINT = 0
-	usb_CDC_ENDPOINT_ACM = 1
-	usb_CDC_ENDPOINT_OUT = 2
-	usb_CDC_ENDPOINT_IN  = 3
-	usb_HID_ENDPOINT_IN  = 4
+	usb_CONTROL_ENDPOINT  = 0
+	usb_CDC_ENDPOINT_ACM  = 1
+	usb_CDC_ENDPOINT_OUT  = 2
+	usb_CDC_ENDPOINT_IN   = 3
+	usb_HID_ENDPOINT_IN   = 4
+	usb_MIDI_ENDPOINT_OUT = 5
+	usb_MIDI_ENDPOINT_IN  = 6
 
 	// bmRequestType
 	usb_REQUEST_HOSTTODEVICE = 0x00
@@ -170,11 +173,13 @@ var (
 	usbSetupHandler [numberOfInterfaces]func(USBSetup) bool
 
 	endPoints = []uint32{
-		usb_CONTROL_ENDPOINT: usb_ENDPOINT_TYPE_CONTROL,
-		usb_CDC_ENDPOINT_ACM: (usb_ENDPOINT_TYPE_INTERRUPT | usbEndpointIn),
-		usb_CDC_ENDPOINT_OUT: (usb_ENDPOINT_TYPE_BULK | usbEndpointOut),
-		usb_CDC_ENDPOINT_IN:  (usb_ENDPOINT_TYPE_BULK | usbEndpointIn),
-		usb_HID_ENDPOINT_IN:  (usb_ENDPOINT_TYPE_DISABLE), // Interrupt In
+		usb_CONTROL_ENDPOINT:  usb_ENDPOINT_TYPE_CONTROL,
+		usb_CDC_ENDPOINT_ACM:  (usb_ENDPOINT_TYPE_INTERRUPT | usbEndpointIn),
+		usb_CDC_ENDPOINT_OUT:  (usb_ENDPOINT_TYPE_BULK | usbEndpointOut),
+		usb_CDC_ENDPOINT_IN:   (usb_ENDPOINT_TYPE_BULK | usbEndpointIn),
+		usb_HID_ENDPOINT_IN:   (usb_ENDPOINT_TYPE_DISABLE), // Interrupt In
+		usb_MIDI_ENDPOINT_OUT: (usb_ENDPOINT_TYPE_DISABLE), // Bulk Out
+		usb_MIDI_ENDPOINT_IN:  (usb_ENDPOINT_TYPE_DISABLE), // Bulk In
 	}
 )
 
@@ -222,6 +227,8 @@ func sendDescriptor(setup USBSetup) {
 		// composite descriptor
 		if (usbDescriptorConfig & usbDescriptorConfigHID) > 0 {
 			usbDescriptor = descriptorCDCHID
+		} else if (usbDescriptorConfig & usbDescriptorConfigMIDI) > 0 {
+			usbDescriptor = descriptorCDCMIDI
 		} else {
 			usbDescriptor = descriptorCDC
 		}
@@ -360,3 +367,12 @@ func EnableHID(txHandler func(), rxHandler func([]byte), setupHandler func(USBSe
 	usbTxHandler[usb_HID_ENDPOINT_IN] = txHandler
 	usbSetupHandler[usb_HID_INTERFACE] = setupHandler // 0x03 (HID - Human Interface Device)
 }
+
+// EnableMIDI enables MIDI. This function must be executed from the init().
+func EnableMIDI(txHandler func(), rxHandler func([]byte), setupHandler func(USBSetup) bool) {
+	usbDescriptorConfig |= usbDescriptorConfigMIDI
+	endPoints[usb_MIDI_ENDPOINT_OUT] = (usb_ENDPOINT_TYPE_BULK | usbEndpointOut)
+	endPoints[usb_MIDI_ENDPOINT_IN] = (usb_ENDPOINT_TYPE_BULK | usbEndpointIn)
+	usbRxHandler[usb_MIDI_ENDPOINT_OUT] = rxHandler
+	usbTxHandler[usb_MIDI_ENDPOINT_IN] = txHandler
+}

src/machine/usb/midi/buffer.go

@@ -0,0 +1,52 @@
+package midi
+
+import (
+	"runtime/volatile"
+)
+
+const bufferSize = 128
+
+// RingBuffer is ring buffer implementation inspired by post at
+// https://www.embeddedrelated.com/showthread/comp.arch.embedded/77084-1.php
+type RingBuffer struct {
+	rxbuffer [bufferSize][4]byte
+	head     volatile.Register8
+	tail     volatile.Register8
+}
+
+// NewRingBuffer returns a new ring buffer.
+func NewRingBuffer() *RingBuffer {
+	return &RingBuffer{}
+}
+
+// Used returns how many bytes in buffer have been used.
+func (rb *RingBuffer) Used() uint8 {
+	return uint8(rb.head.Get() - rb.tail.Get())
+}
+
+// Put stores a byte in the buffer. If the buffer is already
+// full, the method will return false.
+func (rb *RingBuffer) Put(val []byte) bool {
+	if rb.Used() != bufferSize {
+		rb.head.Set(rb.head.Get() + 1)
+		copy(rb.rxbuffer[rb.head.Get()%bufferSize][:], val)
+		return true
+	}
+	return false
+}
+
+// Get returns a byte from the buffer. If the buffer is empty,
+// the method will return a false as the second value.
+func (rb *RingBuffer) Get() ([]byte, bool) {
+	if rb.Used() != 0 {
+		rb.tail.Set(rb.tail.Get() + 1)
+		return rb.rxbuffer[rb.tail.Get()%bufferSize][:], true
+	}
+	return nil, false
+}
+
+// Clear resets the head and tail pointer to zero.
+func (rb *RingBuffer) Clear() {
+	rb.head.Set(0)
+	rb.tail.Set(0)
+}

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)
+	}
+}

src/machine/usb_descriptor.go

@@ -71,3 +71,35 @@ var descriptorCDCHID = USBDescriptor{
 		},
 	},
 }
+
+var descriptorCDCMIDI = USBDescriptor{
+	Device: []byte{
+		0x12, 0x01, 0x00, 0x02, 0xef, 0x02, 0x01, 0x40, 0x86, 0x28, 0x2d, 0x80, 0x00, 0x01, 0x01, 0x02, 0x03, 0x01,
+	},
+	Configuration: []byte{
+		0x09, 0x02, 0xaf, 0x00, 0x04, 0x01, 0x00, 0xa0, 0x32,
+		0x08, 0x0b, 0x00, 0x02, 0x02, 0x02, 0x00, 0x00,
+		0x09, 0x04, 0x00, 0x00, 0x01, 0x02, 0x02, 0x00, 0x00,
+		0x05, 0x24, 0x00, 0x10, 0x01,
+		0x04, 0x24, 0x02, 0x06,
+		0x05, 0x24, 0x06, 0x00, 0x01,
+		0x05, 0x24, 0x01, 0x01, 0x01,
+		0x07, 0x05, 0x81, 0x03, 0x10, 0x00, 0x10,
+		0x09, 0x04, 0x01, 0x00, 0x02, 0x0a, 0x00, 0x00, 0x00,
+		0x07, 0x05, 0x02, 0x02, 0x40, 0x00, 0x00,
+		0x07, 0x05, 0x83, 0x02, 0x40, 0x00, 0x00,
+		0x08, 0x0b, 0x02, 0x02, 0x01, 0x01, 0x00, 0x00,
+		0x09, 0x04, 0x02, 0x00, 0x00, 0x01, 0x01, 0x00, 0x00,
+		0x09, 0x24, 0x01, 0x00, 0x01, 0x09, 0x00, 0x01, 0x03,
+		0x09, 0x04, 0x03, 0x00, 0x02, 0x01, 0x03, 0x00, 0x00,
+		0x07, 0x24, 0x01, 0x00, 0x01, 0x41, 0x00,
+		0x06, 0x24, 0x02, 0x01, 0x01, 0x00,
+		0x06, 0x24, 0x02, 0x02, 0x02, 0x00,
+		0x09, 0x24, 0x03, 0x01, 0x03, 0x01, 0x02, 0x01, 0x00,
+		0x09, 0x24, 0x03, 0x02, 0x04, 0x01, 0x01, 0x01, 0x00,
+		0x09, 0x05, 0x05, 0x02, 0x40, 0x00, 0x00, 0x00, 0x00,
+		0x05, 0x25, 0x01, 0x01, 0x01,
+		0x09, 0x05, 0x86, 0x02, 0x40, 0x00, 0x00, 0x00, 0x00,
+		0x05, 0x25, 0x01, 0x01, 0x03,
+	},
+}