The eurorack 4x4 connection matrix is the little brother of the 8x8 connection matrix.
The first prototype of the bigger matrix was only 4x4. Its form factor of this fitted well with the eurorack format and that made me build the 4x4 version.
With this matrix, you can route 4 input signals (beep boop in) to 4 output signals (beep boop out). You have the ability to save up to 16 patches with the help of the select rotary knob, the load button, and the save button.
In terms of components, both matrices are built around the same core components to make it easy to adapt its software. This version is composed of:
One Arduino mega pro (Similar to Arduino mega but with a smaller footprint)
4 Multiplexers, I used 74HC51 breakout board
One 12 segments display by seeed studio
1 4x4 Neotrellis Keypad by Adafruit
The front panel is made of black anodized aluminum with a bead-blasted finish. I used PCBway services to make this aluminum panel.
A custom 3D printed piece has been made in Fusion 360 to keep the keypad, the Arduino, and the front panel together.
To learn more about how the matrix work, go read the article about its big brother the 8x8 connection matrix.
The matrix has been made for a friend with a modular synthesizer adam.alpaca.music. Take a look of how he used it for a little jam!