ArduinoMIDI2OPZ_BLE.ino

/*   Arduino analog to BLE MIDI
     Ubi de Feo @ Bar Arduino
     https://www.youtube.com/watch?v=0zNmt_IKwRg


     supported boards:
       - Arduino MKR WiFi 1010
       - Arduino Nano 33 IoT
       - Arduino Nano 33 BLE
       - Arduino Nano 33 BLE Sense
       - Arduino UNO WiFI Rev. 2

**** Sketch for USB MIDI version (Nano 33 BLE not supported)                              ****
**** can be found here https://gist.github.com/ubidefeo/6098d95332b6529f1b0599bfd443ebae  ****
**** Thank you Larry Bank for pointing out the lack of a BLE version                      ****


     BLE init code courtesy of T. Igoe
     https://tigoe.github.io/SoundExamples/midi-ble.html
*/

#include <ArduinoBLE.h>
byte midiData[] = {0x80, 0x80, 0x00, 0x00, 0x00};
const byte emptyMIDIMessage[] = {0x80, 0x80, 0x00, 0x00, 0x00};
// set up the MIDI service and MIDI message characteristic:
BLEService midiService("03B80E5A-EDE8-4B33-A751-6CE34EC4C700");
BLECharacteristic midiCharacteristic("7772E5DB-3868-4112-A1A9-F2669D106BF3",
                                     BLEWrite | BLEWriteWithoutResponse |
                                         BLENotify | BLERead,
                                     sizeof(midiData));

bool isMIDIOn = false;
void controlChange(byte channel, byte control, byte value) {
  midiData[2] = 0xB0 | channel;
  midiData[3] = control;
  midiData[4] = value;
  midiCharacteristic.setValue(midiData, sizeof(midiData));
}

const int SAMPLES_COUNT = 20;

// FIFO

int samplesBuffer[SAMPLES_COUNT] = {0};
int sampleIndex = 0;

const int knobInputPin = A1;
const int changeThreshold = 20;

int lastSensorValue;
int lastMappedValue;
unsigned long samplesSum = 0;

void setup() {
  Serial.begin(57600);
  delay(5000);

  // Initialize BLE:
  if (!BLE.begin()) {
    Serial.println("starting BLE failed!");
    while (true)
      ;
  }
  // set local name and advertised service for BLE:
  BLE.setLocalName("ARDUINO_MIDI_BLE");
  BLE.setAdvertisedService(midiService);

  // add the characteristic and service:
  midiService.addCharacteristic(midiCharacteristic);
  BLE.addService(midiService);

  // start advertising
  BLE.advertise();

  Serial.println("SETUP");
}

void loop() {
  int knobReadOut = filterAnalogValue(knobInputPin);
  int mappedValue = map(knobReadOut, 0, 1023, 0, 127);

  BLEDevice central = BLE.central();

  // When a central is connected to the peripheral we initially send
  // an empty MIDI command in order to let certain platforms acknowledge the MIDI device
  // Once that is done we set isMIDIOn to true and do not send the empty message until
  // a reconnection happens upon disconnection (isMIDIOn needs to be false)
  if (central && !isMIDIOn) {
    midiCharacteristic.setValue(emptyMIDIMessage, sizeof(emptyMIDIMessage));
    isMIDIOn = true;
  }else{
    isMIDIOn = false;
  }
  if(isMIDIOn){
    if (lastMappedValue != mappedValue) {
      // Serial.println("************ CHANGE ***************");
      // Serial.print(">>> ");
      // Serial.print(mappedValue);
      // Serial.println(" <<<");
      controlChange(0, 4, mappedValue);
    }
    lastMappedValue = mappedValue;
  }
  //delay(100);
}

int filterAnalogValue(int _inputPin) {
  samplesSum = 0;
  int analogValue = analogRead(_inputPin);
  // int valueDelta = abs(analogValue - lastSensorValue);
  // Serial.print(analogValue);
  // Serial.print(" - ");
  // Serial.println(lastSensorValue);
  // if(valueDelta < changeThreshold){
  //     analogValue = lastSensorValue;
  // }
  if (sampleIndex < SAMPLES_COUNT) {
    samplesBuffer[sampleIndex] = analogValue;
    sampleIndex++;
  } else {
    for (int samplePosition = 0; samplePosition < sampleIndex - 1;
         samplePosition++) {
      0;
      samplesBuffer[samplePosition] = samplesBuffer[samplePosition + 1];
    }
    samplesBuffer[SAMPLES_COUNT - 1] = analogValue;
  }
  for (int samplePosition = 0; samplePosition < sampleIndex; samplePosition++) {
    0;
    samplesSum += samplesBuffer[samplePosition];
  }
  // lastSensorValue = analogValue;

  if (samplesSum == 0)
    return 0;
  unsigned int filteredValue = samplesSum / sampleIndex;
  return filteredValue;
}