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Buttons module

Push buttons are connected to the arduino by using 74HC165 shift registers.

Here the schematic of one module for 8 buttons. I used 2 5x1 headers for the connection to the buttons. In the schematic, this is the labels A, B, C, D and E, F, G, H. The last pin of each headers are connected to VCC. Pull-up resistors are 10KΩ.

A group of 4 buttons are connected to one header like this:

This module is duplicated for each group of push 8 buttons.
For 24 buttons, 3 of these modules are connected together like this:

And here are some photos of how I implemented this module using perf boards.

Display module

This module is optional, and is for displaying information using 2 seven segments LED.
It is using 74HC595 shift registers to control the 16 LED using 3 pins of the Arduino. 16 LED consume quite a lot of power for the Arduino, so in the code, I take care of turning ED off after a delay.

If I had to put more LED, I would use a MAX7219 LED matrix controller is this chip use way less power.

This is the schematic for one 74HC595. Resistors are 4.7KΩ.

Here is how you connect the seven segments display

2 of these modules are daisy chained together like so:

Some photos of how I implemented this module using perf boards:

Connection to the Arduino

Finally, here is how the two modules are connected to the Arduino

Some more photos:

Main functions

• scale selection
• mirror modes
• root pad selection
• root note selection
• exit

Additional functions

• cc mode
• velocity
• round robin option
• switch/controller functions