JTK – Notes and Ramblings Things we have found …

Some time ago a Mighty Mule FM231 Driveway Alarm was installed. This is an electromagnetic inductive sensor with a transmitter and indoor receiver. Various ways of linking this to Openhab were considered. Since an sdr is already setup and configured to handle the LaCrosse weather station, the best solution seems to be to use a rtl_433 decoder to generate messages to the MQTT broker.

Once you have rtl_433 setup with your sdr, the next step is to add the decoder to your rtl_433.conf file:

decoder {
    name=MightyMule-FM231,
    modulation=OOK_PWM,
    short=650,
    long=1200,
    sync=3800,
    reset=1100,
    rows=1,
    bits=9,
    get=@4:{1}:battery_ok:[0:1 1:0],
    get=@5:{4}:id,
    get=@0:{1}:motion:[0:true 1:true],
    unique
}

The next step is to assure you have rtl_433 setup to send MQTT messages to your broker:

output mqtt://broker_ip_address,devices=rtl_433/garage[/model]

For me this results in messages that look something like:

rtl_433/garage/MightyMule-FM231/time 2023-01-22 11:39:48.795951
rtl_433/garage/MightyMule-FM231/count 1
rtl_433/garage/MightyMule-FM231/num_rows 1
rtl_433/garage/MightyMule-FM231/len 9
rtl_433/garage/MightyMule-FM231/data 728
rtl_433/garage/MightyMule-FM231/battery_ok 1
rtl_433/garage/MightyMule-FM231/id 5
rtl_433/garage/MightyMule-FM231/motion true
rtl_433/garage/MightyMule-FM231/mod ASK
rtl_433/garage/MightyMule-FM231/freq 433.98368
rtl_433/garage/MightyMule-FM231/rssi -0.124222
rtl_433/garage/MightyMule-FM231/snr 25.3924
rtl_433/garage/MightyMule-FM231/noise -25.5166

With this all setup, a Openhab Generic MQTT Thing was created with a Channel for the MQTT topic “rtl_433/garage/MightyMule-FM231/motion”. Two items were created, one for the channel itself and a second linking to the channel with a “Timestamp on Change” profile. Metadata for an Expiration Timer was added to the motion item to reset(the unit never sends motion false).