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:
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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:

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Schematic:

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Wiring:

Then I replaced the original chip with a Blue Pill module and added a USB connector:
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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.
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• Patchage: Provides a graphical interface to connect jack and midi inputs and outputs.
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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)

• 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.
  

Have fun :-)

diff -r 75d307e38488 -r 41d2a3984dd7 MidiKey.cpp
--- a/MidiKey.cpp	Wed Apr 08 17:47:23 2020 +0000
+++ b/MidiKey.cpp	Thu Apr 09 08:23:32 2020 +0000
@@ -18,6 +18,4 @@
         _position == 1 ? _midi.write(MIDIMessage::NoteOn(_note)) : _midi.write(MIDIMessage::NoteOff(_note));
         _lastPos = _position;
     }
-
-    wait_ms(2);
 }

diff -r 75d307e38488 -r 41d2a3984dd7 main.cpp
--- a/main.cpp	Wed Apr 08 17:47:23 2020 +0000
+++ b/main.cpp	Thu Apr 09 08:23:32 2020 +0000
@@ -67,6 +67,7 @@
     while (1) {
         for (uint8_t i = 0; i < keyLen; i++) {
             key[i].scan();
+            wait_ms(2);
         }
     }
 }