A while ago I received a couple of I/O port expander modules that use the I 2 C protocol. Using that Chinese module, you can use only the SDA and SCL pins of your Arduino, or any microcontroller ...
Apogee Semiconductor proudly announces APIO16, the industry’s first radiation-hardened 16-bit I/O expander, engineered to streamline digital expansion in spaceborne and high-reliability terrestrial ...