@lmwcoding/node-red-contrib-lywsd02 0.1.0

Node-RED nodes to read Xiaomi LYWSD02MMC temperature/humidity sensors via a reliable BLE GATT connection

npm install @lmwcoding/node-red-contrib-lywsd02

@lmwcoding/node-red-contrib-lywsd02

Node-RED nodes to read Xiaomi LYWSD02MMC temperature/humidity sensors via a reliable BLE GATT connection (not passive scanning).

Why this palette?

Passive BLE scanning of the LYWSD02MMC is unreliable — the device advertises in short bursts and you frequently miss readings. This palette establishes a real GATT connection, subscribes to the data characteristic, and reads the battery characteristic, giving you a consistent reading every time.

How it works

The Node-RED nodes are written in JavaScript. For the low-level BLE I/O they shell out to a bundled Python helper (lib/ble-helper.py) that uses bleak. bleak talks to BlueZ over D-Bus, which is the most reliable way to do BLE on Linux (the same layer bluetoothctl uses). Pure-JS BLE libraries (e.g. @abandonware/noble) use raw HCI sockets and are unreliable on many modern Linux/BlueZ setups.

Installation

npm install @lmwcoding/node-red-contrib-lywsd02

Prerequisites

1. Python 3 with the bleak package:

   pip3 install bleak
   

   (or install into a virtualenv and point the node at that interpreter)

2. Bluetooth running on the host (bluetooth service active).

3. On Linux, the user running Node-RED should be in the bluetooth group:

   sudo usermod -aG bluetooth <user>
   

   (then restart Node-RED)

Nodes

lywsd02-config (config node)

lywsd02-read (function node)

Send any message to this node to trigger a read. The output is:

msg.payload = { temperature: 25.3, humidity: 60, battery: 85 }
msg.topic   = "<config name>"
msg.mac     = "<MAC>"
msg.error   = "<message>"   // only on failure

The node status shows the latest reading (green/yellow/red by battery level).

Example

[inject: every 5 min] --> [lywsd02-read] --> [debug / ui-chart / ...]

See examples/lywsd02-example.json for an importable flow.

Notes

• Only one GATT connection to a LYWSD02MMC is allowed at a time. The helper clears any stale connection before reading, so repeated reads are safe.
• A read takes roughly 2–5 seconds (connect + notify + battery read).

License

MIT