Add up to 128 I/O Pins to your ESP Board

 

While it may not have happened to you yet, there may come a time when you need more inputs and outputs than can be connected to the default GPIO pins of a single ESP8266 or ESP32 board.  While there are many different types of port expanders and multiplexers available for ESP-based boards, this article is going to take a look at one of those options:  The MCP23017 16-Port Digital I/O expander.