SimpleSensing_ESP32.ino

#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

uint8_t note = 38;
int SNARE[6] = {150, 4000, 38, 3, 0, 0}; //{threshold, sensitivity, note(no use), flag, velocity, last peakValue}
boolean snareFlag = false;

BLECharacteristic *pCharacteristic;
bool deviceConnected = false;

#define MIDI_SERVICE_UUID        "03b80e5a-ede8-4b33-a751-6ce34ec4c700"
#define MIDI_CHARACTERISTIC_UUID "7772e5db-3868-4112-a1a9-f2669d106bf3"

uint8_t midiPacket[] = {
  0x80,  // header
  0x80,  // timestamp, not implemented
  0x00,  // status
  0x3c,  // 0x3c == 60 == middle c
  0x00   // velocity
};

class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
      deviceConnected = true;
    };

    void onDisconnect(BLEServer* pServer) {
      deviceConnected = false;
    }
};

void setup() {
  Serial.begin(115200);

  BLEDevice::init("MIDI"); //Device Name

  // Create the BLE Server
  BLEServer *pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());
  BLEDevice::setEncryptionLevel((esp_ble_sec_act_t)ESP_LE_AUTH_REQ_SC_BOND);

  // Create the BLE Service
  BLEService *pService = pServer->createService(BLEUUID(MIDI_SERVICE_UUID));

  // Create a BLE Characteristic
  pCharacteristic = pService->createCharacteristic(
                      BLEUUID(MIDI_CHARACTERISTIC_UUID),
                      BLECharacteristic::PROPERTY_READ   |
                      BLECharacteristic::PROPERTY_NOTIFY |
                      BLECharacteristic::PROPERTY_WRITE_NR
                    );
  pCharacteristic->setAccessPermissions(ESP_GATT_PERM_READ_ENCRYPTED | ESP_GATT_PERM_WRITE_ENCRYPTED);

  // https://www.bluetooth.com/specifications/gatt/viewer?attributeXmlFile=org.bluetooth.descriptor.gatt.client_characteristic_configuration.xml
  // Create a BLE Descriptor
  pCharacteristic->addDescriptor(new BLE2902());

  // Start the service
  pService->start();

  // Start advertising

  BLESecurity *pSecurity = new BLESecurity();
  pSecurity->setAuthenticationMode(ESP_LE_AUTH_REQ_SC_BOND);
  pSecurity->setCapability(ESP_IO_CAP_NONE);
  pSecurity->setInitEncryptionKey(ESP_BLE_ENC_KEY_MASK | ESP_BLE_ID_KEY_MASK);

  pServer->getAdvertising()->addServiceUUID(MIDI_SERVICE_UUID);
  pServer->getAdvertising()->start();

}

void loop() {
  if (deviceConnected) {

    //Sensing Start
    int piezoValue = analogRead(33);

    if (piezoValue > SNARE[0] && snareFlag == false) {

      for (int i = 0; i < 4; i++) {
        int peak = analogRead(33);
        delay(1);

        if (peak > SNARE[4]) {
          SNARE[4] = peak;
        }
      }

      SNARE[5] = SNARE[4];
      SNARE[4] = map(SNARE[4], SNARE[0], SNARE[1], 0, 127);

      if (SNARE[4] <= 1) {
        SNARE[4] = 1;
      }

      if (SNARE[4] > 127) {
        SNARE[4] = 127;
      }
      //Sensing Done

      // noteOn
      midiPacket[2] = 0x90; // note down, channel 0
      midiPacket[3] = note; //snare note is 38
      midiPacket[4] = SNARE[4];  // velocity
      pCharacteristic->setValue(midiPacket, 5); // packet, length in bytes
      pCharacteristic->notify();
      // noteOff
      midiPacket[2] = 0x80; // note up, channel 0
      midiPacket[3] = note; //snare note is 38
      midiPacket[4] = 0;    // velocity
      pCharacteristic->setValue(midiPacket, 5); // packet, length in bytes)
      pCharacteristic->notify();

      snareFlag = true;
    }

    //Canceling Retrigger
    if (piezoValue < (SNARE[5] * (0.01 * SNARE[3])) && snareFlag == true) {
      delay(3); //mask time
      int sensorValue0 = analogRead(33);
      if (sensorValue0 < (SNARE[5] * (0.01 * SNARE[3]))) {
        snareFlag = false;
      }
    }
  }
}

Hi there, this code works fine for me.
How i add another piezo in this code?