How to Connect an MCP23008 I/O Port Expander to an Arduino
I<sup>2</sup>C-IO-Expander
MCP23017 I2C 16 input/output port expander
MCP23017 - i2c 16 Input/Output Port Expander : Amazon.de: Toys
OPEN SMART PCF8575 IO Expander Modul I2C zu 16IO I2C zu 16 bit IO expansion breakout board für Arduino|module i2c|module for arduinomodule diy - AliExpress
LinuxCNC Documentation Wiki: Shift Register Port Expander