Interfacing a Character LCD via SPI

Modern microcontrollers are packed with memory and processing power, but often don't have enough pins for everything we want to connect. A classic example is driving an HD44780-compatible LCD display — a great choice for simple user interfaces, but one that normally demands a lot of I/O lines. In this project, I'll show you how to control one of these displays over a simple SPI connection, using just a handful of wires and a cheap shift register. We'll build a tiny daughterboard to handle the conversion, set up a minimal breadboard circuit for testing, and walk through exactly how to send data to the LCD. Along the way, I'll also point you toward some tools that make experimenting even easier.