GPIO Expansion

74HC595 Complete Guide (2026): Wiring and Arduino Code

A thorough guide to using the 74HC595 with Arduino. Expand your GPIO without limit using just three signal lines — from shiftOut() to hardware SPI, with schematics, KiCad design files, and sample code. Fully compatible with the Arduino UNO R4.

MCP23017 with ESP32: I2C Address Setup and 16 GPIO Pins

A complete guide to the MCP23017 I/O expander with schematics. Add 16 GPIO pins to an ESP32 over I2C, set the address with A0–A2, and drive 8 LEDs and 3 switches with the Adafruit_MCP23X17 library. Step by step, with full sample code.