1. Introduction

Many car doors use a small sensor exactly like this one to detect whether the door is open or closed, without any physical contact between the door and the sensing element. In this experiment, a reed switch is used to detect the presence of a nearby magnet, and the STM32F070RB simply lights an LED whenever that magnet is close enough to close the switch.

2. Scope

This experiment covers reading a reed switch as a simple digital input with an internal pull-up enabled, and directly driving an LED output to match its current state. This is one of the more straightforward digital sensor readings in this entire series, useful as a quick, confidence-building exercise in GPIO input handling.

3. Prerequisite

3.1 Hardware

• STM32 Nucleo-F070RB development board

• Reed switch module

• A small magnet, to trigger the switch

• LED and a 220 ohm resistor

• Breadboard and jumper wires

• Micro-USB cable

3.2 Software

• STM32CubeMX (standalone)

• STM32CubeIDE

• ST-LINK USB driver