Add 16 I/O Pins with a PCF8575
A small PCF8575 module gives Arduino, ESP8266, or ESP32 projects 16 extra digital lines through just SDA and SCL. This hands-on setup uses LEDs and buttons to test the connection, while a library handles the I2C details and leaves the host board’s built-in pins available.
Read the build on mischianti.org: Add 16 I/O Pins with a PCF8575Featured in TinkerNews Issue 37 ·
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Read the build on github.com: Build a Wi-Fi Four-Fan Controller