Description

The box accepts multiple switch inputs. Any momentary contact switch is supported via 3.5mm (1/8in) jack inputs. The note, MIDI channel and velocity of each switch is independantly set using the rotary encoder.

Hardware

The control box is based on an Arduino Nano. Switch inputs are 3.5mm jack sockets using the arduinos internal pullups. A rotary encooder is used to control option menus displayed on a Nokia 5110 lcd diaplay. Switch presses are shown by LEDs above each input, due to a shortage of IO pins these are controlled via a 74hc595 shift register. MIDI signals are then sent through a standard 5pin DIN socket.

Arduino pin allocations

TX0	MIDI out
2,3,4	rotary encoder
5,6,7,8	lcd display
9	lcd backlight
10,11,12	shift register
A0-A5	switch inputs

Components

Switch inputs

A variety of switches can be used. Although primeraly designed for buddy/jelly bean switches any momentary contact switch can be used. The inputs are pulled high using the arduino INPUT_PULLUP with the switches pulling low.

Shift register

For simplicty I would have connected each indicator LED to its own output pin, however the Arduino Nano doesn’t have enough pins. Charlieplexing would have been an option if only 1 LED was ever lit at a time. Since I will need miltiple LEDs lit I decided to use a shift register. This allows me to independantly control the 6 LEDs with only 3 ouput pins.

LCD display

The LCD is controlled with the PCD8544 library. RST, DC, DIN and SCLK are connected to pins 5,6,7 and 8. Since these are all 3.3V lines, they have to go theough a level shifter. CS is tied to GND. The LED backlight is controlled by pin 9.

Rotary encoder

As the rotary encoder uses Interupts it is connected to pins 2 and 3. The press switch on it is commected to pin 4.

MIDI out

The MIDI signal is connected through a 220ohm resister to the TX0 pin of the arduino.

Enclosure

The box was designed in Fusion 360 and 3D printed in PLA.

Software

TODO

Add battery and charger circuit.

Github Repository