Ubiquiti mFi Custom Code

Custom firmware applications for Ubiquiti's mFi line of power monitoring and switching devices. Includes an MQTT client for Home Assistant integration, a REST API server, and a CLI tool — all built on a shared C++ library that wraps the mFi hardware interface.

Architecture

mfi-mqtt-client ─┬─ hass_mqtt_device (Home Assistant MQTT discovery)
                 ├─ mfi (hardware abstraction: sensors, relays, LEDs)
                 ├─ mfi-update (self-update from GitHub Releases)
                 └─ shmuelie-shared (string utilities)

mfi-rest-server ─┬─ civetweb (embedded HTTP server, C++ API)
                 ├─ mfi
                 ├─ mfi-update
                 └─ shmuelie-shared

mfi-cli ─────────┬─ mfi
                 ├─ mfi-update
                 └─ shmuelie-shared

Projects

Executables

Project	Description	Version
mfi-mqtt-client	MQTT client with Home Assistant auto-discovery	1.2.1
mfi-rest-server	HTTP REST API server	1.2.2
mfi-cli	CLI tool for device inspection and control	1.1.0

Libraries

Project	Description	Version
mfi	Hardware abstraction for sensors, relays, LEDs	1.0.1
hass_mqtt_device	Home Assistant MQTT device library	1.2.0
mfi-update	Self-update from GitHub Releases	1.0.0
shmuelie-shared	String helper functions	1.0.0

Alternatives

There are several community shell-script projects for controlling mFi devices. This project differs in being a compiled C++ solution with a proper hardware abstraction layer, native MQTT, and Home Assistant auto-discovery.

Feature	mfi-custom-code	mpower-tools	mFi-tools
Language	C++	Shell scripts	Shell scripts
MQTT	Native (libmosquitto)	Via mosquitto_pub	Via mosquitto_pub
Home Assistant	Auto-discovery (switches + sensors)	Manual YAML config	Manual YAML config
REST API	Yes (civetweb)	No	No
CLI tool	Yes	No	No
Sensor data	Power, current, voltage, power factor	Power, energy	Power, energy
Change-only updates	Yes (reduces MQTT traffic)	No (polls on interval)	No (polls on interval)
Hardware abstraction	C++ library	Direct file I/O	Direct file I/O
Cross-compilation	Buildroot toolchain	Not needed	Not needed
Unit tests	Catch2	None	None
Install complexity	Build + deploy binary	Copy scripts	Copy scripts

Documentation

• Building — packages, CMake presets, build commands, testing
• Deploying — binary sizes, UPX, boot scripts, SCP
• Updating — self-update from GitHub Releases
• mFi Notes — persistent storage, save, boot hooks
• cfgmtd — flash configuration utility internals