MIDI-Monitor-OLED.ino

MIDI-Monitor-OLED

This example shows all incoming and outgoing MIDI messages on an SSD1306 OLED display. This can be handy for debugging purposes when you don't have access to the Serial Monitor.

Boards: 🛈

AVR, Nano Every, Due, Nano 33 IoT, Nano 33 BLE, UNO R4, Teensy 3.x, ESP32, ESP8266

Connections

• 5: Push button (to ground)
• MOSI: OLED Data/D1 (SPI)
• SCK: OLED Clock/D0 (SPI)
• 8: OLED Reset
• 9: OLED Data/Command
• 10: OLED Cable Select

Behavior

• When sending MIDI messages to the Arduino using the USB interface, these messages are printed on the OLED display, prefixed by a right arrow (→).
• If any MIDI messages are sent by Control Surface (e.g. by pressing the push button), these messages are printed on the OLED display, prefixed by a left arrow (←).
  
  

Explanation

The code below defines the OLEDDebugMIDI_Output class, which implements the MIDI_Sink and MIDI_Sender interfaces. This means that it can accept MIDI messages coming from MIDI_Pipes, and it provides all of the usual functions for sending MIDI messages.

The MIDI over USB interface (midi) will be used as the primary MIDI interface (as in the other Control Surface examples).
Two instances of our OLEDDebugMIDI_Output class are created: one for printing messages that are received by the primary MIDI interface, and one for printing messages that are sent by Control Surface.
The MIDI interfaces and Control Surface itself are connected appropriately using some pipes.

See also

MIDI_Pipes-Routing.ino

Debug-MIDI-Interface.ino

MIDI Tutorial: Routing MIDI messages

MIDI-Monitor.ino

Written by PieterP, 2024-01-05
https://github.com/tttapa/Control-Surface

 
#include <Adafruit_SSD1306.h>
#include <Control_Surface.h>
 
// Specify the options and pins for the display
constexpr uint8_t SCREEN_WIDTH = 128;
constexpr uint8_t SCREEN_HEIGHT = 64;
constexpr int8_t OLED_reset = 8; // Reset pin of the display
constexpr int8_t OLED_DC = 9;    // Data/Command pin of the display
constexpr int8_t OLED_CS = 10;   // Chip Select pin of the display
constexpr uint32_t SPI_Frequency = SPI_MAX_SPEED;
 
Adafruit_SSD1306 disp {
  SCREEN_WIDTH, SCREEN_HEIGHT, &SPI,          OLED_DC,
  OLED_reset,   OLED_CS,       SPI_Frequency,
};
 
void init_display() {
  if (!disp.begin())
    FATAL_ERROR(F("SSD1306 allocation failed."), 0x1306);
  disp.setTextColor(SSD1306_WHITE);
  disp.setTextSize(1);
  disp.cp437();
  disp.clearDisplay();
  disp.display();
  disp << uppercase;
}
 
// Shifts the entire display up by the given number of lines and sets the
// cursor at the beginning of the first of the newly created empty lines.
void shift_display(uint8_t lines = 1) {
  auto buf = disp.getBuffer();
  auto end = buf + SCREEN_WIDTH * SCREEN_HEIGHT / 8;
  std::move(buf + lines * SCREEN_WIDTH, end, buf);
  std::fill(end - lines * SCREEN_WIDTH, end, 0);
  disp.setCursor(0, SCREEN_HEIGHT - 8 * lines);
}
 
constexpr const char *abbrev_midi_status_names[] {
  "Note Off", "Note On", "Key Pres",  "Ctrl Ch",
  "Prog Ch",  "Ch Pres", "Pitch Bend"};
 
class OLEDDebugMIDI_Output : public MIDI_Sender<OLEDDebugMIDI_Output>,
                             public TrueMIDI_Sink {
 public:
  OLEDDebugMIDI_Output(const char *prefix = nullptr) : prefix(prefix) {}
 
  // Implement the required MIDI_Sink interface
  void sinkMIDIfromPipe(ChannelMessage m) override { send(m); }
  void sinkMIDIfromPipe(SysExMessage m) override { send(m); }
  void sinkMIDIfromPipe(SysCommonMessage m) override { send(m); }
  void sinkMIDIfromPipe(RealTimeMessage m) override { send(m); }
 
 private:
  // Implement the required MIDI_Sender interface
  friend MIDI_Sender<OLEDDebugMIDI_Output>;
  void sendChannelMessageImpl(ChannelMessage msg) {
    uint8_t messageType = (msg.header >> 4) - 8;
    if (messageType >= 7)
      return;
    shift_display(1);
    if (prefix != nullptr)
      disp << prefix << ' ';
    if (print_cable)
      disp << msg.getCable().getOneBased() << ':';
    disp << msg.getChannel().getOneBased() << ' ';
    disp << abbrev_midi_status_names[messageType];
    if (msg.getMessageType() == msg.PitchBend)
      disp << ' ' << hex << msg.getData14bit() << 'h' << dec;
    else if (msg.hasTwoDataBytes())
      disp << ' ' << hex << msg.getData1() << 'h' << ' ' << msg.getData2()
           << 'h' << dec;
    else
      disp << abbrev_midi_status_names[messageType] << ' ' << hex
           << msg.getData1() << 'h' << dec;
    disp.display();
  }
  void sendSysCommonImpl(SysCommonMessage msg) {
    shift_display(1);
    if (prefix != nullptr)
      disp << prefix << ' ';
    if (print_cable)
      disp << msg.getCable().getOneBased() << ' ';
    disp << msg.getMessageType() << hex;
    if (msg.getNumberOfDataBytes() >= 1)
      disp << ' ' << msg.getData1() << 'h';
    if (msg.getNumberOfDataBytes() >= 2)
      disp << ' ' << msg.getData2() << 'h';
    disp << dec;
    disp.display();
  }
  void sendSysExImpl(SysExMessage msg) {
    const uint16_t bytes_per_line = 7;
    uint8_t lines = (msg.length + bytes_per_line - 1) / bytes_per_line;
    shift_display(1 + lines);
    if (prefix != nullptr)
      disp << prefix << ' ';
    if (print_cable)
      disp << msg.getCable().getOneBased() << ' ';
    disp << F("Sys Ex [") << msg.length << (msg.isLastChunk() ? "]" : "+]");
    uint16_t i = 0;
    while (i < msg.length) {
      uint16_t rem = msg.length - i;
      uint16_t len = std::min(bytes_per_line, rem);
      disp.println();
      disp << ' ' << AH::HexDump(msg.data + i, len);
      i += bytes_per_line;
    }
    disp.display();
  }
  void sendRealTimeImpl(RealTimeMessage msg) {
    shift_display(1);
    if (prefix != nullptr)
      disp << prefix << ' ';
    if (print_cable)
      disp << msg.getCable().getOneBased() << ' ';
    disp << msg.getMessageType();
    disp.display();
  }
  void sendNowImpl() {}
 
  // Prefix is printed in front of every message
  const char *prefix;
  // Print the USB cable number
  bool print_cable = false;
};
 
// Main MIDI interface used by Control Surface
USBMIDI_Interface midi;
// Prints messages being received to the display
OLEDDebugMIDI_Output midi_disp_in {"\x1a"}; // prefix="→"
// Prints messages being sent to the display
OLEDDebugMIDI_Output midi_disp_out {"\x1b"}; // prefix="←"
// Two pipes for MIDI routing
MIDI_PipeFactory<2> pipes;
 
// MIDI element to send messages for testing
NoteButton button {5, MIDI_Notes::C[4]};
 
void setup() {
  init_display();
  midi.setAsDefault();
  Control_Surface.begin();
  // Route MIDI messages to the display
  midi >> pipes >> midi_disp_in;
  Control_Surface >> pipes >> midi_disp_out;
}
 
void loop() {
  Control_Surface.loop();
}