add USB disconnect failsafe

Emulator/patches/MIDI.cpp.patch

@@ -20,8 +20,7 @@
 48a46,47
 > }
 > 
-338,346d336
-< 
+339,354d337
 < #ifdef PRINTMIDI
 <   SerialUSB.print("MIDI: ");
 <   SerialUSB.print(byte1, HEX);
@@ -30,7 +29,7 @@
 <   SerialUSB.print(" ");
 <   SerialUSB.println(byte3, HEX);
 < #endif
-348,354d337
+< 
 <   // Pass MIDI though to hardware port
 <   if(Serial.availableForWrite() >= 3) { // Rush E protection
 <     Serial.write(byte1);
@@ -44,7 +43,9 @@
 <     return;
 <   }
 <   LCD::MIDIping(channel);
-387,413d364
+385,409d362
+<   }
+< }
 < 
 < void initMIDI() {
 < #ifdef PRINTMIDI
@@ -68,6 +69,30 @@
 <       hwMIDIbufInd = 0;
 <       handleMIDI(hwMIDIbuf[0], hwMIDIbuf[1], hwMIDIbuf[2]);
 <     }
+412,438d364
+< 
+< void checkConnected() {
+<   static uint16_t lastFrameNumber;
+<   static int8_t missedFrameCount = -1;
+< 
+<   // Should increment at 1ms USB frame interval
+<   const uint16_t frameNumber = (UOTGHS->UOTGHS_DEVFNUM & UOTGHS_DEVFNUM_FNUM_Msk) >> UOTGHS_DEVFNUM_FNUM_Pos;
+< 
+<   if(frameNumber == lastFrameNumber) {
+<     // Only count missed frames if we have received some in the past
+<     if(missedFrameCount >= 0)
+<       missedFrameCount++;
+<   }
+< 
+<   else missedFrameCount = 0;
+< 
+<   lastFrameNumber = frameNumber;
+< 
+<   // Disable oscillators if we go more than 10ms without a USB frame
+<   if(missedFrameCount >= 10) {
+<     missedFrameCount = -1;
+<     for(int x=0; x<NVOICES; x++)
+<         Voice::voices[x].active = false;
 <   }
 < }
 < 

Emulator/patches/MIDI.h.patch

@@ -13,10 +13,11 @@
 > 
 > static constexpr float midi2freq[] = {8.18,8.66,9.18,9.72,10.30,10.91,11.56,12.25,12.98,13.75,14.57,15.43,16.35,17.32,18.35,19.45,20.60,21.83,23.12,24.50,25.96,27.50,29.14,30.87,32.70,34.65,36.71,38.89,41.20,43.65,46.25,49.00,51.91,55.00,58.27,61.74,65.41,69.30,73.42,77.78,82.41,87.31,92.50,98.00,103.83,110.00,116.54,123.47,130.81,138.59,146.83,155.56,164.81,174.61,185.00,196.00,207.65,220.00,233.08,246.94,261.63,277.18,293.66,311.13,329.63,349.23,369.99,392.00,415.30,440.00,466.16,493.88,523.25,554.37,587.33,622.25,659.26,698.46,739.99,783.99,830.61,880.00,932.33,987.77,1046.50,1108.73,1174.66,1244.51,1318.51,1396.91,1479.98,1567.98,1661.22,1760.00,1864.66,1975.53,2093.00,2217.46,2349.32,2489.02,2637.02,2793.83,2959.96,3135.96,3322.44,3520.00,3729.31,3951.07,4186.01,4434.92,4698.64,4978.03,5274.04,5587.65,5919.91,6271.93,6644.88,7040.00,7458.62,7902.13,8372.02,8869.84,9397.27,9956.06,10548.08,11175.30,11839.82,12543.85};
 > 
-140,141d145
+140,142d145
 < void initMIDI();
+< void checkConnected();
 < void processMIDI();
-143c147
+144c147
 < }
 ---
 > };

Tesla_Coil_MIDI_Synth/MIDI.cpp

@@ -410,4 +410,29 @@ void processMIDI() {
   }
 }
 
+void checkConnected() {
+  static uint16_t lastFrameNumber;
+  static int8_t missedFrameCount = -1;
+
+  // Should increment at 1ms USB frame interval
+  const uint16_t frameNumber = (UOTGHS->UOTGHS_DEVFNUM & UOTGHS_DEVFNUM_FNUM_Msk) >> UOTGHS_DEVFNUM_FNUM_Pos;
+
+  if(frameNumber == lastFrameNumber) {
+    // Only count missed frames if we have received some in the past
+    if(missedFrameCount >= 0)
+      missedFrameCount++;
+  }
+
+  else missedFrameCount = 0;
+
+  lastFrameNumber = frameNumber;
+
+  // Disable oscillators if we go more than 10ms without a USB frame
+  if(missedFrameCount >= 10) {
+    missedFrameCount = -1;
+    for(int x=0; x<NVOICES; x++)
+        Voice::voices[x].active = false;
+  }
+}
+
 }

Tesla_Coil_MIDI_Synth/MIDI.h

@@ -138,6 +138,7 @@ void pitchBend(uint8_t channel, uint8_t low7, uint8_t high7);
 void cc(uint8_t channel, uint8_t control, uint8_t value);
 void handleMIDI(unsigned char byte1, unsigned char byte2, unsigned char byte3);
 void initMIDI();
+void checkConnected();
 void processMIDI();
 
 }

Tesla_Coil_MIDI_Synth/Tesla_Coil_MIDI_Synth.ino

@@ -36,6 +36,7 @@ void loop() {
 
 extern "C" {
 int sysTickHook() { // Runs at 1kHz
+  MIDI::checkConnected();
   Synth::updateSynth();
   return 0;
 }