Zoltan Hudak / Mbed 2 deprecated MidiKeyboardToy

Converting Piano Toy to MIDI Keyboard.

Dependencies:   mbed mbed-STM32F103C8T6 USBDevice_STM32F103

How to turn kids' old piano toy to a MIDI keyboard

Inspired by http://www.codetinkerhack.com/2012/11/how-to-turn-piano-toy-into-midi.html I did the same with a Blue Pill module using Mbed.

The old toy was capable to play only one tone at a time:
Zoom in
https://os.mbed.com/media/uploads/hudakz/minikeyboardtoy01.jpg



A bit of reverse-engineering was needed to re-use the original printed boards. The results are below.

Original PCBs with switches traced to the connector pins:

Zoom in
https://os.mbed.com/media/uploads/hudakz/keys.jpg Zoom in
https://os.mbed.com/media/uploads/hudakz/buttons.jpg

Schematic:

Zoom in
https://os.mbed.com/media/uploads/hudakz/schematic.png

Wiring:

https://os.mbed.com/media/uploads/hudakz/wiring.png



Then I replaced the original chip with a Blue Pill module and added a USB connector:
Zoom in
https://os.mbed.com/media/uploads/hudakz/minikeyboardtoy02.jpg

Works great when connected over an USB cable to a Linux Ubuntu 18.04 machine

Installed software:

  • Yoshimi: An excellent MIDI software synthesizer for Linux.
    Zoom in
    https://os.mbed.com/media/uploads/hudakz/yoshimi.png
  • Patchage: Provides a graphical interface to connect jack and midi inputs and outputs.
    Zoom in
    https://os.mbed.com/media/uploads/hudakz/patchage.png

How to use it:

  • Connect the Keyboard to the PC over an USB cable.
  • Run Yoshimi.
  • Run Patchage and connect the Mbed USB Audio MIDI 1 output to Yoshimi's input (drag Mbed Audio MIDI 1 over yoshimi input and drop)

https://os.mbed.com/media/uploads/hudakz/connection.png

  • To apply the changes close the Patchage!
  • On Yoshimi's toolbar click on Instruments and select Show Stored ...
  • Select a bank and click on the instrument you'd like to play.
    https://os.mbed.com/media/uploads/hudakz/instruments.png

Have fun :-)

MidiKey.cpp@1:41d2a3984dd7, 2020-04-09 (annotated)

Committer:
hudakz
Date:
Thu Apr 09 08:23:32 2020 +0000
Revision:
1:41d2a3984dd7
Parent:
0:75d307e38488 
Converting Piano Toy to MIDI Keyboard.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
hudakz 0:75d307e38488 1 #include "MidiKey.h"
hudakz 0:75d307e38488 2
hudakz 0:75d307e38488 3 /**
hudakz 0:75d307e38488 4 * @brief
hudakz 0:75d307e38488 5 * @note
hudakz 0:75d307e38488 6 * @param
hudakz 0:75d307e38488 7 * @retval
hudakz 0:75d307e38488 8 */
hudakz 0:75d307e38488 9 void MidiKey::scan()
hudakz 0:75d307e38488 10 {
hudakz 0:75d307e38488 11 _row.output();
hudakz 0:75d307e38488 12 _row.mode(PullUp);
hudakz 0:75d307e38488 13 _row = 1;
hudakz 0:75d307e38488 14 _position = _col.read();
hudakz 0:75d307e38488 15 _row.input();
hudakz 0:75d307e38488 16 _row.mode(PullDown);
hudakz 0:75d307e38488 17 if (_position != _lastPos) {
hudakz 0:75d307e38488 18 _position == 1 ? _midi.write(MIDIMessage::NoteOn(_note)) : _midi.write(MIDIMessage::NoteOff(_note));
hudakz 0:75d307e38488 19 _lastPos = _position;
hudakz 0:75d307e38488 20 }
hudakz 0:75d307e38488 21 }