Implement MIDI read and write.

4 files changed, 132 insertions, 1 deletions

diff --git a/avr/cores/arcore/MIDIUSB.cpp b/avr/cores/arcore/MIDIUSB.cpp
index 925cdf7..aeec8a7 100644
--- a/avr/cores/arcore/MIDIUSB.cpp
+++ b/avr/cores/arcore/MIDIUSB.cpp
@@ -2,6 +2,7 @@
 #include "Platform.h"
 #include "USBAPI.h"
 #include "USBDesc.h"
+#include "MIDIUSB.h"
 
 #if defined(USBCON)
 #ifdef MIDI_ENABLED
@@ -71,5 +72,89 @@ bool WEAK MIDI_Setup(Setup& setup)
     return false;
 }
 
+const MIDIEvent MIDI_EVENT_NONE = {0, 0, 0, 0};
+
+
+void MIDIUSB_::accept(void) 
+{
+    midi_buffer *buffer = &(this->_rx_buffer);
+    int i = (unsigned int)(buffer->head+1) % MIDI_BUFFER_SIZE;
+    
+    // if we should be storing the received character into the location
+    // just before the tail (meaning that the head would advance to the
+    // current location of the tail), we're about to overflow the buffer
+    // and so we don't write the character or advance the head.
+
+    // while we have room to store a byte
+    while (i != buffer->tail) {
+        int c = USB_Recv(CDC_RX);
+        if (c == -1)
+            break;  // no more data
+        buffer->buffer[buffer->head] = c;
+        buffer->head = i;
+
+        i = (unsigned int)(buffer->head+1) % MIDI_BUFFER_SIZE;
+    }
+}
+
+int MIDIUSB_::available(void)
+{
+    midi_buffer *buffer = &(this->_rx_buffer);
+    return ((unsigned int)(MIDI_BUFFER_SIZE + buffer->head - buffer->tail) % MIDI_BUFFER_SIZE) / 4;
+}
+
+MIDIEvent MIDIUSB_::peek(void)
+{
+    if(this->available() < 4) {
+        return MIDI_EVENT_NONE;
+    } else {
+        midi_buffer *buffer = &(this->_rx_buffer);
+        MIDIEvent result;
+        result.type = buffer->buffer[buffer->tail];
+        result.m1 = buffer->buffer[(buffer->tail+1) % MIDI_BUFFER_SIZE];
+        result.m2 = buffer->buffer[(buffer->tail+2) % MIDI_BUFFER_SIZE];
+        result.m3 = buffer->buffer[(buffer->tail+3) % MIDI_BUFFER_SIZE];
+        return result;
+    }
+}
+
+MIDIEvent MIDIUSB_::read(void)
+{
+    MIDIEvent event = this->peek();
+    midi_buffer *buffer = &(this->_rx_buffer);
+    buffer->tail = (unsigned int)(buffer->tail + 4) % MIDI_BUFFER_SIZE;
+    return event;
+}
+
+void MIDIUSB_::flush(void)
+{
+    USB_Flush(MIDI_TX);
+}
+
+size_t MIDIUSB_::write(MIDIEvent c)
+{
+    // TODO: only try to send bytes if the connection is open
+    
+    int r = USB_Send(MIDI_TX,&c,4);
+    if (r > 0) {
+        return r;
+    } else {
+        return 0;
+    }
+}
+
+// This operator is a convenient way for a sketch to check whether the
+// port has actually been configured and opened by the host (as opposed
+// to just being connected to the host).  It can be used, for example, in 
+// setup() before printing to ensure that an application on the host is
+// actually ready to receive and display the data.
+// This is not actually implemented yet (always returns true).
+MIDIUSB_::operator bool() {
+    return true;
+}
+
+MIDIUSB_ MIDIUSB;
+
+
 #endif
 #endif
diff --git a/avr/cores/arcore/MIDIUSB.h b/avr/cores/arcore/MIDIUSB.h
index e69de29..5410867 100644
--- a/avr/cores/arcore/MIDIUSB.h
+++ b/avr/cores/arcore/MIDIUSB.h
@@ -0,0 +1,5 @@
+#if defined(USBCON)
+#ifdef MIDI_ENABLED
+
+#endif
+#endif
\ No newline at end of file
diff --git a/avr/cores/arcore/USBAPI.h b/avr/cores/arcore/USBAPI.h
index f12277e..4c1852f 100644
--- a/avr/cores/arcore/USBAPI.h
+++ b/avr/cores/arcore/USBAPI.h
@@ -44,6 +44,47 @@ public:
 };
 extern Serial_ Serial;
 
+
+//================================================================================
+//================================================================================
+//  MIDI_USB
+
+#define MIDI_BUFFER_SIZE 64
+
+struct midi_buffer
+{
+    unsigned char buffer[MIDI_BUFFER_SIZE];
+    volatile int head;
+    volatile int tail;
+};
+
+typedef struct
+{
+    uint8_t type;
+    uint8_t m1;
+    uint8_t m2;
+    uint8_t m3;
+} MIDIEvent;
+
+extern const MIDIEvent MIDI_EVENT_NONE;
+
+class MIDIUSB_
+{
+private:
+    midi_buffer _rx_buffer;
+public:
+
+    virtual int available(void);
+    virtual void accept(void);
+    virtual MIDIEvent peek(void);
+    virtual MIDIEvent read(void);
+    virtual void flush(void);
+    virtual size_t write(MIDIEvent);
+    operator bool();
+};
+extern MIDIUSB_ MIDIUSB;
+
+
 //================================================================================
 //================================================================================
 //	Mouse
diff --git a/avr/cores/arcore/USBCore.cpp b/avr/cores/arcore/USBCore.cpp
index 735ca18..686a2e8 100644
--- a/avr/cores/arcore/USBCore.cpp
+++ b/avr/cores/arcore/USBCore.cpp
@@ -630,7 +630,7 @@ ISR(USB_GEN_vect)
 			Serial.accept();
 #endif
 #ifdef MIDI_ENABLED
-		// TODO: implement midi receive here
+		MIDIUSB.accept();
 #endif
 		// check whether the one-shot period has elapsed.  if so, turn off the LED
 		if (TxLEDPulse && !(--TxLEDPulse))