(EN) DIY Guitar Stompbox - The A-1 Buffer

This is my new stomp box: the A-1 Buffer pedal. It is very simple, very small, transparent and beautiful (IMHO).

It is based on on an N-type JFET and its circuit has very few components, making it a good first project

(EN) MCP23017 I/O port expander - How to use it with Arduino

The MCP23017 chip is I/O port expander that uses the I2C communication protocol. You can connect it to your Arduino using only two pins (those needed for I2C communication) and get 16 more digital I/O ports in return.

Furthermore you can chain up to eight expander in series and get 128 digital ports, always at the small cost of two pins.

This is a simple circuit to explain you how to connect and use the MCP23017: connect a momentary button