Gatecontrol

Go service for a Raspberry Pi Zero W operating a FAAC-E124 gate control unit through a DIDO relay board and MQTT.

Overview

The service subscribes to MQTT commands, pulses the DIDO relay connected to the FAAC IN 1 input, and publishes the assumed gate state back to MQTT.

There is no USB FAAC protocol support in this project. The FAAC control is operated through the existing DIDO board only.

MQTT Topics

The MQTT base topic defaults to faac/gate.

faac/gate/command

Inbound command topic. Supported payloads:

open
close

faac/gate/state

Retained state topic. Published payloads:

OPEN
CLOSED

The service starts with assumed state CLOSED. Because no feedback pins are connected yet, this state is based on the last successful command, not on real gate position.

faac/gate/target_state

Retained target topic. Published payloads:

open
close

faac/gate/availability

Retained availability topic. Published payloads:

online
offline

Gate Hardware

The hardware that is used to control the entrance gate is a FAAC-E124 Control Unit.

The FAAC unit is extended with:

• Raspberry Pi Zero W
• DIDO module with MCP23S17-compatible SPI GPIO expander
• 4 Channel Optocoupler
• USB Powerconverter

Circuit Diagram

These components need to be connected according to the following circuit diagram:

FAAC-E124 Control Unit Configuration

Please refer to the FAAC-E124 manual for details on the control unit. Chapter 5 of the document explains how to program the device.

The following values need to be configured:

LO = E or EP
o1 = 05
o2 = 06

Setting LO to either E or EP configures input IN 1 to operate the gate semi-automatically: a first impulse opens the gate, a second impulse closes it.

o1 and o2 are documented for future input feedback. The current Go service does not read those outputs yet.

Configuration

Environment variables:

• MQTT_BROKER (default: localhost): MQTT broker hostname or IP address
• MQTT_PORT (default: 1883): MQTT broker port
• MQTT_CLIENT_ID (default: gatecontrol): MQTT client id
• MQTT_USERNAME: optional MQTT username
• MQTT_PASSWORD: optional MQTT password
• MQTT_BASE_TOPIC (default: faac/gate): MQTT base topic
• LOG_LEVEL (default: info): debug, info, warn, or error
• SPI_BUS (default: 0): SPI bus used by the DIDO board
• SPI_CHIP_SELECT (default: 0): SPI chip select used by the DIDO board
• SPI_HARDWARE_ADDR (default: 0): MCP23S17 hardware address
• DIDO_RELAY_PIN (default: 0): DIDO output pin used for the relay
• SPI_SPEED_HZ (default: 100000): SPI transfer speed
• PULSE_LENGTH_MS (default: 500): relay active time and follow-up delay
• USE_MOCK_DIDO (default: false): use in-memory DIDO mock
• USE_MOCK_MQTT (default: false): use in-memory MQTT mock

Build

Local build:

go build ./cmd/gatecontrol

Run tests:

go test ./...

Cross-compile for the original Raspberry Pi Zero W:

GOOS=linux GOARCH=arm GOARM=6 CGO_ENABLED=0 go build -o bin/gatecontrol-armv6 ./cmd/gatecontrol

Raspberry Pi Setup

Enable SPI on the Pi:

sudo raspi-config

Then check that a device such as /dev/spidev0.0 exists:

ls -l /dev/spidev*.*

Copy the compiled binary to the Pi, for example:

scp bin/gatecontrol-armv6 pi@ip_address_of_pi_zero:/home/pi/gatecontrol/gatecontrol

Adjust gatecontrol.service, copy it to /lib/systemd/system, and enable the service:

sudo systemctl daemon-reload
sudo systemctl enable gatecontrol.service
sudo systemctl start gatecontrol.service

Local Mock Run

The mock DIDO backend mimics the relay pulse sequence without touching /dev/spidev*.

USE_MOCK_DIDO=true USE_MOCK_MQTT=true go run ./cmd/gatecontrol

Current Limitations

The service does not read gate feedback inputs yet. It assumes the gate is initially CLOSED and updates the state after successful commands. The assumed state can be wrong if the gate is operated by another remote, keypad, wall switch, safety stop, obstacle detection, or power interruption.

Related Projects

• FAAC-E145-Gate-Connect - similar FAAC work for a different board and protocol