Introduction

This experiment is about controlling something bigger than the chip itself can safely handle directly. We'll wire up a relay module and switch it on or off using the exact same UART menu style we built back in Experiment 2, type 1, the relay clicks on; type 2, it clicks off. It's a small demo, but the underlying idea (a tiny microcontroller safely controlling something much more powerful) is exactly how a car's ECU switches on a fuel pump or how a smart-home hub turns on a light socket.

2. Scope

We'll look at why relays exist in the first place, wire up a GPIO pin to control one, and reuse the print_str()/read_line() helper functions from Experiment 2 rather than rebuilding them from scratch, which is a nice little lesson in itself: once you've built a solid piece of reusable code, you don't need to reinvent it every time.

3. Prerequisite

3.1 Hardware

• STM32 Nucleo-F070RB development board

• A 5V single-channel relay module

• Breadboard and jumper wires

• Micro-USB cable

• PC with PuTTY

3.2 Software

• STM32CubeMX (standalone)

• STM32CubeIDE

• ST-LINK USB driver

• PuTTY, or an equivalent serial terminal app