This Arduino sketch allows you to create a MIDI button controller using shift registers. It reads the state of buttons connected to shift registers and sends MIDI notes accordingly.

• Arduino board compatible with MIDIUSB library
• MIDI USB cable
• Shift registers (e.g., 74HC595)
• Momentary push buttons

Certainly! Here's how you can connect a 4x4 button matrix to two 74HC165 shift registers in a grid layout:

In a 4x4 button matrix layout, the buttons are typically numbered sequentially from left to right, top to bottom. Here's how the buttons would be numbered in a 4x4 grid:

16 15 14 13
12 11 10 9
8  7  6  5
4  3  2  1

Each number corresponds to a physical button in the matrix. For example, button 1 is the top-left button, button 2 is the button next to it to the right, and so on. This numbering scheme allows you to easily identify each button's position in the matrix.

1. Connect your Arduino board to your computer via USB.
2. Upload the sketch to your Arduino board.
3. Connect the shift registers and buttons according to the circuit diagram.
4. Use the buttons to trigger MIDI notes. Pressing a button sends a MIDI note-on message, and releasing it sends a MIDI note-off message.

The sketch uses the MIDIUSB library to send MIDI messages via USB. It reads the state of buttons connected to shift registers by shifting in their states using the shiftIn function. When a button is pressed, it sends a MIDI note-on message, and when it's released, it sends a MIDI note-off message.

This sketch is adapted from Arduino MIDI Button Controller example provided by the MIDIUSB library.

This project is licensed under the MIT License - see the LICENSE file for details.