Golang Xiaomi Bluetooth Temperature|Humidity (LYWSD03MMC) 2nd Gen

Credits:

• Jonathan McDowell for gomijia and help
• JsBergbau for help

Summary

The LYWSD03MMC is a second-generation Xiaomi Thermometer|Humidity sensor. The device is BLE-enabled and (supposedly) works in conjunction with the Mi Home app (though I've been unsuccessfully in connecting my devices with the app). I plan to connect the (4) devices that I bought (for $20) to ESPs running the most-excellent ESPHome but, until new ESP devices arrive, I was interested in connecting to the devices using Golang.

I found Jonathan's gomijia but this does not work with these second-generation devices. Thanks to Jonatha for his code and his help. After much hacking around, I learned two key facts:

• The LYWSD03MMC devices don't advertise the temperature & humidity; instead a connection must be made to the device
• Somehow (!) clever folks (see JsBergbau's working Python code) worked out how to receive notifications from the devices (see below)

Running

You'll need:

• At least 1 LYWSD03MMC and you'll want the MAC addresses for your devices.
• An MQTT broker to publish temperature|humidity readings

Create a configuration file and enumerate your devices and their MAC addresses:

[MQTT]
host=localhost
port=1883
#user=user
#pass=pass

[Devices]
device1=a4:c1:38:11:11:11
device2=a4:c1:38:22:22:22
...

You'll need to run the code as root because of the BLE connecting:

${which go} run github.com/DazWilkin/gomijia2 --config_file=/path/to/config.ini

You'll receive lots of logging output but you should see:

[main] Reading configuration
[Config] Loading Configuration (./config.ini)
[Config] Device 00: xiaomi1 (a4:c1:38:00:00:00)
[Config] Device 01: xiaomi2 (a4:c1:38:00:00:00)
[Config] Device 02: xiaomi3 (a4:c1:38:00:00:00)
[Config] Device 03: xiaomi4 (a4:c1:38:00:00:00)
[main] Starting Linux Device
[main] MQTT broker: tcp://lcoalhost:1883
[MQTT:Connect] Connecting: xiaomi
[MQTT] Creating
[MQTT] Connecting
[main:xiaomi1] Dialing (a4:c1:38:3c:7c:e7)
[main:xiaomi1] Registering handler
[main:xiaomi1] (0035) Registering Temperature|Humidity Handler
[main:xiaomi2] Dialing (a4:c1:38:00:00:00)
...
[handler:xiaomi1] Temperature: 22.0300; Humidity: 0.4200 (9b082ab90b)
[handler:xiaomi2] Temperature: 21.5600; Humidity: 0.4200 (6c082a600b)
[handler:xiaomi4] Temperature: 22.2900; Humidity: 0.4100 (b50829dd0b)
[handler:xiaomi3] Temperature: 22.0900; Humidity: 0.4200 (a1082ada0a)
[handler:xiaomi1] Temperature: 22.0000; Humidity: 0.4200 (98082ab90b)
[handler:xiaomi2] Temperature: 21.6000; Humidity: 0.4200 (70082a600b)
[handler:xiaomi4] Temperature: 22.3100; Humidity: 0.4100 (b70829dd0b)

NB I've removed some entries from the above for clarity

I've configured Inuits MQTTGateway to subscribe to topics and expose these as Prometheus metrics.

I've configured Prometheus to scrape the MQTTGateway metrics.

Here's the result: