Unix style IoT with MQTT.

Instead of developing YAMS (yet another monolithic solution) I'm trying to develop a bunch of small and independent softwares that communicate using MQTT that I call homely.

This tools are written in golang so they will not kill your Raspberry PI and should also be reasonably easy to adapt and extend in case they do not fit your exact needs.

You need to install golang first, then you can use the go tool to install homely with all the needed dependency with the following lines:

export GOPATH=~/go
export PATH=$PATH:$GOPATH/bin

go get -u github.com/baol/homely/...
go install github.com/baol/homely/...

A Unix background :)

A Linux computer (e.g. Raspberry PI) with some kind or IoT devices attached (433MHz, Z-Wave, ZigBee, or whatever).

An MQTT broker running on one of your machines (the reference implementation available at https://mosquitto.org/ will do, as should any packaged version).

In the following examples we will assume that the machine running MQTT is reachable at the address mqtt.local.

Recently services like https://www.cloudmqtt.com/ started to happear and they offer a free plan if you need to reach your broker from the public internet, but for our examples installing mosquitto on your Raspberry PI should be enough.

A Domoticz user wants to receive Desktop notifications every time the Main door of his apartment opens.

For this we will need the hl-telegram, hl-notify, hl-wiring and hl-domofilter modules.

First we need to configure domoticz to forward his messages to MQTT, so we go to the Hardware section and add a new "MQTT Client Gateway with LAN Interface" configured to forward all the messages to homely.local in the Flat (default) format.

Unfortunately Domoticz choice of topics does not fit well with homely so we need to run

hl-domofilter --mqtt tcp://mqtt.local:1883

To process some interesting Domoticz events and republish them as homely events. Assuming our main door sensor has id 2 (look in Domoticz Devices to know the id you are interested in), when the door will open this will publish a message to homely/status/2/On.

We also need to run the notifier

hl-notify --mqtt tcp://mqtt.local:1883

that will listen homely/notify/send for messages in the format {"message": "Main door open"} and send them to your desktop on Mac OS or Linux.

In order to wire the two together we also need hl-wiring

Edit ~/.homely/wiring.toml and write your rule there using the same id mentioned above:

[rule."homely/status/2/On"."homely/notification/send"]
payload = '{"message": "Main door open"}'

Now launch

hl-wiring --mqtt tcp://mqtt.local:1883

And enjoy your notifications!

• hl-telegram works the same way as hl-notify, but you first need to register your bot with the @BotFather and know the numeric userid you want to send notifications to. In order to know your id, send a message to your bot and go to

    https://api.telegram.org/bot<BOT-KEY>/getUpdates
  

  (replace <BOT-KEY> with the key received from the BotFather)

• hl-flag works together with an Arduino powered physical notificatin devices to raise a flag on certain events, and can be controlled sending empty messages to homely/flag/up and homely/flag/down. See Materia Flag for details about the device.

  To wire your main door events to the Materia Flag add the following rules in wiring.toml

    [rule."homely/status/2/Off"."homely/flag/down"]
    [rule."homely/status/2/On"."homely/flag/up"]
  

Wiring can also be used to automate other actions, like switching off the lights when you turn on the TV: all messages sent to homely/command/<ID>/On and homely/command/<ID>/Off will be translated in Domoticz commands by hl-domofilter.

Happy hacking!