Midi Controller with Arduino and some Piezo elements

Since I discovered that a Piezo Element could be used an Midi input with velocity and that it cost only $1, I was really eager to try.

In short you get what you paid for, though it works,

• The sensitivity is not great at least when you want to use your finger to trigger a sound
• The latency is too long (see image from  blog post Spooky Arduino Projects #4 – Musical Arduino. It can take up to 80 ms for one tap to return to 0.

Anyway, here is the schema, with one Piezo. You can plug more as long as you have Analog input pin available. Noticed that each Piezo has a 1Mega Ohm resistor in parallel.

Video

In this video one of the Piezo did not work well, but in general even with the one that work, I could not get the speed and sensitivity needed. I need to try better sensor.

Here is main source code that read 4 piezo elements and trigger different sound on a MIDI keyboard.

The source of the Piezo class is available in the file fArduino.cpp.

#include "MIDI.h"
#include 
#include 

// Pins usage
#define ON_BOARD_LED 13
#define MIDI_IN_PIN  2
#define MIDI_OUT_PIN 3
#define PIEZO_1_PIN  0

Led _onBoardLed(ON_BOARD_LED);
boolean _ledState = false;

SoftwareSerial _softwareSerial(MIDI_IN_PIN, MIDI_OUT_PIN);
MIDI_CREATE_INSTANCE(HardwareSerial, _softwareSerial, MIDI);

#define YPT210_DRUM_CHANNEL 10

// YPT-210 Standard Kit 1, Midi note
#define BD_SOFT             33
#define BD                  36
#define BD_HARD             35
#define SD                  38
#define SD_HARD             40
#define HAND_CLAP           39
#define HH_CLOSED           42
#define HH_PEDAL            44
#define HH_OPEN             46
#define CYMBAL_CRASH_1      49
#define CYMBAL_CRASH_2      57
#define CYMBAL_SPLASH       55
#define CYMBAL_CHINESE      52
#define CYMBAL_RIDE_1       51
#define CYMBAL_RIDE_2       59
#define TOM_FLOOR_L         41
#define TOM_FLOOR_H         43
#define TOM_MID_L           47
#define TOM_MID_H           48
#define TOM_HIGH            50
#define TAMBOURINE          54

int     _channel = YPT210_DRUM_CHANNEL;

void setup() {

    Board.Delay(1500); // Wait 1.5 second before initializing the serial com, so  I can start the ArduinoWindowsConsole on the Windows machine
    Board.InitializeComputerCommunication(9600, "Initializing...");
    Board.TraceHeader("Finger Drummer");

    Board.SetPinMode(ON_BOARD_LED, OUTPUT);
    _onBoardLed.SetBlinkMode(500);

    _softwareSerial.begin(31250);
    MIDI.begin();

    Board.Trace(StringFormat.Format("Playing _channel:%d", _channel));
}

void ShowUserInfo() {

    Board.SendWindowsConsoleCommand(StringFormat.Format("user info"), false, true);
}

void TestMidi(int channel) {

    for (byte note = 30; note < 90; note++) {

        MIDI.sendNoteOn(note, 64, channel);
        delay(20);
        MIDI.sendNoteOff(note, 0, channel);
        delay(5);
    }
}
void ProcessWindowsConsoleCommand() {

    if (Serial.available()) {

        WindowsCommand winCommand = Board.GetWindowsConsoleCommand(); // The WindowsConsole method use the Serial port communication
        if (winCommand.Command == "testMidi") {
            TestMidi(1);
            TestMidi(10);
        }
        else {
            if (winCommand.Command != "") {
                Board.SendWindowsConsoleCommand(StringFormat.Format("[Invalid command:%s]", winCommand.Command.c_str()), false, true);
            }
        }
    }
}


#define PIEZOTHRESHOLD 10
#define HITHAT_MAX_VALUE 250
#define SD_MAX_VALUE 1000
#define BD_MAX_VALUE 1000

Piezo fingerHitHat  (1, PIEZOTHRESHOLD, HITHAT_MAX_VALUE, 127);
Piezo fingerHitHat2 (2, PIEZOTHRESHOLD, HITHAT_MAX_VALUE, 127);
Piezo fingerSD      (3, PIEZOTHRESHOLD, SD_MAX_VALUE, 90);
Piezo fingerBD      (0, PIEZOTHRESHOLD, BD_MAX_VALUE, 100);


void loop() {

    String buf("");
    _onBoardLed.Blink();

    /// http://todbot.com/arduino/sketches/midi_drum_kit/midi_drum_kit.pde

    int v1 = fingerHitHat.GetValue();
    if (v1 != -1) {
        MIDI.sendNoteOn(HH_CLOSED, v1, _channel);
    }

    v1 = fingerHitHat2.GetValue();
    if (v1 != -1) {
        MIDI.sendNoteOn(HH_CLOSED, v1, _channel);
    }

    v1 = fingerSD.GetValue();
    if (v1 != -1) {
        MIDI.sendNoteOn(SD_HARD, v1, _channel);
    }

    v1 = fingerBD.GetValue();
    if (v1 != -1) {
        MIDI.sendNoteOn(BD, v1, _channel);
        MIDI.sendNoteOn(HH_CLOSED, v1 - (v1*20/100), _channel);
    }

    ProcessWindowsConsoleCommand();
}