MQTT Publisher in C

A lightweight MQTT publisher written in C that reads a GPIO line using libgpiod and publishes a message to an MQTT broker using libmosquitto.

Files

• main.c – Program entry; reads GPIO and publishes MQTT messages in a loop.
• gpio_reader.c / gpio_reader.h – Minimal wrapper around libgpiod for initializing, reading, and closing a GPIO line.

Build Instructions

Compile with gcc, linking against libmosquitto and libgpiod.

Example:

gcc main.c gpio_reader.c -o mqtt-publisher -lmosquitto -lgpiod

Configuration

• Edit the constants GPIO_LINE and MQTT_HOST in main.c to match your setup before building.

Notes

• Designed for Raspberry Pi 5
• Requires libgpiod and libmosquitto development libraries.