SwitchBotMeter2MQTT-Python

A lightweight Python-based Bluetooth Low Energy (BLE) scanner that reads temperature, humidity, battery level, and RSSI from SwitchBot Meter devices and publishes the values to MQTT. This project is ideal for:

• Home automation systems (ioBroker, Home Assistant, Node-RED, OpenHAB)
• Raspberry Pi or Linux-based gateways
• Users who want a simple, dependency-light alternative to ESP32-based solutions

✨ Features

• Scans for SwitchBot Meter BLE advertisements using bluepy
• Correctly decodes negative temperatures (including sub-zero values)
• Extracts:
• Temperature (°C)
• Humidity (%)
• Battery level (%)
• RSSI (dBm)
• Publishes all values to MQTT in the format: SwitchBot2MQTT// Example: SwitchBot2MQTT/ce:2a:81:86:4d:2c/temp SwitchBot2MQTT/ce:2a:81:86:4d:2c/hum SwitchBot2MQTT/ce:2a:81:86:4d:2c/bat SwitchBot2MQTT/ce:2a:81:86:4d:2c/rssi
• Filters out corrupted BLE frames
• Optional debug output
• Optional WhatsApp alert on BLE scan failure (via user-provided function)

🧠 SWITCHBOT BLE PAYLOAD FORMAT

SwitchBot Meter broadcasts a 16‑byte BLE Service Data frame: Byte 0–3: Header Byte 4: Battery level (0–100%) Byte 5: Temperature low byte Byte 6: Temperature high byte (bit 7 = sign, bits 0–6 = integer part) Byte 7: Humidity (0–100%)

✔Correct Temperature Decoding (including negative values):

SwitchBot uses a sign bit in the high byte: bit 7 = 1 → positive temperature bit 7 = 0 → negative temperature Remaining 7 bits = integer part Low byte = decimal part (0–9) Formula:

int_part = temp_high & 0x7F
dec_part = temp_low / 10.0
if temp_high & 0x80:
temp = int_part + dec_part     # positive
else:
temp = -(int_part + dec_part)  # negative

Example:

Raw bytes: 01 04 integer = 4 decimal = 0.1 sign bit = 0 (negative) temperature = -4.1°C This decoding method fixes the common “-127°C bug” seen in many scripts online.

🚀 INSTALLATION

• Install dependencies: sudo apt install python3-pip bluetooth bluez pip3 install bluepy paho-mqtt
• Clone the repository: git clone https://github.com//SwitchBotMeter2MQTT-Python cd SwitchBotMeter2MQTT-Python
• Run the script: python3 switchbot2mqtt.py

🔧 CONFIGURATION

Inside the script:

• Add your MQTT server credentials
• Add your known SwitchBot MAC addresses (optional)
• Enable debug output if needed

📡 MQTT OUTPUT EXAMPLE

SwitchBot2MQTT/ce:23:45:67:89:0e/temp -4.1
SwitchBot2MQTT/ce:23:45:67:89:0e/hum 57
SwitchBot2MQTT/ce:23:45:67:89:0e/bat 89
SwitchBot2MQTT/ce:23:45:67:89:0e/rssi -91

🛠 SYSTEMD SERVICE (optional)

Create: /etc/systemd/system/switchbot2mqtt.service Content: [Unit] Description=SwitchBot Meter BLE to MQTT After=bluetooth.target [Service] ExecStart=/usr/bin/python3 /path/to/switchbot2mqtt.py Restart=always [Install] WantedBy=multi-user.target Enable: sudo systemctl enable --now switchbot2mqtt

This project was developed to provide a clean, reliable, and fully documented Python alternative to ESP32-based SwitchBot Meter integrations.

LICENSE

MIT License

Why This Project Exists

Many SwitchBot Meter BLE decoders on the internet incorrectly interpret the temperature bytes, especially for negative values. This leads to impossible readings like -127.8°C or +102°C.

This repository documents the correct decoding logic based on the actual BLE payload structure and provides a working Python implementation.

Example BLE Payloads

Raw ServiceData: 3D FD 54 00 E4 02 00 57
Decoded temperature: -0.2°C

Raw ServiceData: 3D FD 54 00 E4 01 04 51
Decoded temperature: -4.1°C