I control a few devices from the Internet, but I don’t want all devices exposed and connected to IoT Central. One solution is to build a gateway locally which routes request messages to switch things on or off to the correct device locally.
In this post we will look at how to send commands from IoT Central and route them using Node-RED to the automation device via MQTT.
This architure uses Node-RED as a gateway, and then uses Eclipse Mosquito as a MQTT server. The Grow Light and Air Conditioner in the diagram is an off the shelf Sonoff POW-R2 device flashed with Tasmota.
Installing Eclipse Mosquitto in a Container
Installing Node-RED in a Container
With Node-RED you can visually map the flow / sequence of events. Node-RED supports Azure IoT Hubs and Azure IoT Central, so it’s perfect for this job to do quickly and easily without having to write code.
In Azure IoT Central we have a single device linked with a command. The command accepts a parameter, which will be the device name / topic name on the local MQTT server.
The diagram above shows the command with the parameter.
The Node-RED Azure component supports Direct Methods. These are commands that you can directly invoke on a device. In this case, the device is the gateway itself created within Node-RED.
It supports two methods (as per Azure IoT Central template)
- turngatewaydeviceon
- turngatewaydeviceoff
With a Node-Red switch statement we can controll the flow with whichever method name was invoked from IoT Central.
If it’s the “DeviceOn” flow, then the device parameter name (payload) is used to build up the topic for the Sonoff device via MQTT. The payload of the message will be “on”.
If it’s the “DeviceOff” flow, then the device parameter name (payload) is used to build up the topic for the Sonoff device via MQTT. The payload of the message will be “off”.
