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Temp and RH Monitor Lite

About CGDK2

  • Qingping 'Temp & RH Monitor Lite' CGDK2 are hygrometers
  • Has sensors to relay temperature and humidity
  • Uses Bluetooth Low Energy (BLE) and has a limited range
  • A CR2430 coin cell battery is used as power source

Features

  • Read real-time sensor values
  • Read historical sensor values
  • Temperature and humidity sensors

Protocol

The device uses BLE GATT for communication.
Sensor values are immediately available for reading.

BLE & GATT

The basic technologies behind the sensors communication are Bluetooth Low Energy (BLE) and GATT. They allow the devices and the app to share data in a defined manner and define the way you can discover the devices and their services. In general you have to know about services and characteristics to talk to a BLE device.

Endianness

Data structure

Bluetooth payload data typically uses little-endian byte order.
This means that the data is represented with the least significant byte first.

To understand multi-byte integer representation, you can read the endianness Wikipedia page.

Services, characteristics and handles

The name advertised by the devices is Qingping Temp RH Lite.

Generic access (UUID 00001800-0000-1000-8000-00805f9b34fb)
Generic attribute (UUID 00001801-0000-1000-8000-00805f9b34fb)
Device information (UUID 0000180a-0000-1000-8000-00805f9b34fb)
Data service (UUID 22210000-554a-4546-5542-46534450464d)
Characteristic UUID Handle Access Description
00000100-0000-1000-8000-00805f9b34fb - notify real time data

Communication with the device

Register to get notification on the 'real time data' characteristic.
The device will send back 7 bytes data packets:

Bytes Type Value Description
00-01 bytes ?
02 byte 236 battery voltage?
03-04 int16_le 198 / 10 = 19.8 temperature in °C
05-06 int16_le 578 / 10 = 57.8 humidity in % RH

Historical data

TODO

Advertisement data

There seems to be two kind of advertisement data broadcasted.
CGDK2 broadcast service data with 16 bits service UUID 0xFE95 and 0xFDCD.

UUID 0xFE95 12 bytes messages

The CGDK2 has 'fixed content' MiBeacon data. No actionable data. Encrypted?

Check out the MiBeacon protocol page to get more information on advertisement data for this device.

UUID 0xFDCD 17 bytes messages

CGDK2 broadcast temperature, humidity, and battery over service data with the 0xFDCD 16 bits service UUID.

Check out the Qingping protocol page to get more information on advertisement data for this device.

Reference

[1] -

License

MIT