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I have a bluetooth device that is measuring the force and basically sends one single value. There is an android app to connect to it, but I would like to develop my own since I would like to add some features. I managed to connect to it, but don't know which service or characteristics is the one that has the number I need. Someone could maybe know which of these it could be?

Service 00001801-0000-1000-8000-00805f9b34fb

Characteristics:
|--00002a05-0000-1000-8000-00805f9b34fb

Service 00001800-0000-1000-8000-00805f9b34fb

Characteristics:
|--00002a00-0000-1000-8000-00805f9b34fb
|--00002a01-0000-1000-8000-00805f9b34fb
|--00002a04-0000-1000-8000-00805f9b34fb

Service a9712440-a0e8-11e6-bdf4-0800200c9a66

Characteristics:
|--a9712441-a0e8-11e6-bdf4-0800200c9a66
|--a9712442-a0e8-11e6-bdf4-0800200c9a66
|--a9712443-a0e8-11e6-bdf4-0800200c9a66

Service a970fd30-a0e8-11e6-bdf4-0800200c9a66

Characteristics:
|--a970fd31-a0e8-11e6-bdf4-0800200c9a66
|--a970fd32-a0e8-11e6-bdf4-0800200c9a66
|--a970fd33-a0e8-11e6-bdf4-0800200c9a66
|--a970fd34-a0e8-11e6-bdf4-0800200c9a66
|--a970fd35-a0e8-11e6-bdf4-0800200c9a66
|--a970fd36-a0e8-11e6-bdf4-0800200c9a66
|--a970fd37-a0e8-11e6-bdf4-0800200c9a66
|--a970fd38-a0e8-11e6-bdf4-0800200c9a66
|--a970fd39-a0e8-11e6-bdf4-0800200c9a66
|--a970fd3a-a0e8-11e6-bdf4-0800200c9a66
|--a970fd3b-a0e8-11e6-bdf4-0800200c9a66

Service a9717260-a0e8-11e6-bdf4-0800200c9a66

Characteristics:
|--a9717261-a0e8-11e6-bdf4-0800200c9a66
|--a9717262-a0e8-11e6-bdf4-0800200c9a66
|--a9717263-a0e8-11e6-bdf4-0800200c9a66
|--a9717264-a0e8-11e6-bdf4-0800200c9a66
|--a9717265-a0e8-11e6-bdf4-0800200c9a66
|--a9717266-a0e8-11e6-bdf4-0800200c9a66
|--a9717267-a0e8-11e6-bdf4-0800200c9a66
|--a9717268-a0e8-11e6-bdf4-0800200c9a66
|--a9717269-a0e8-11e6-bdf4-0800200c9a66
|--a971726a-a0e8-11e6-bdf4-0800200c9a66
|--a971726b-a0e8-11e6-bdf4-0800200c9a66
|--a971726c-a0e8-11e6-bdf4-0800200c9a66
|--a971726d-a0e8-11e6-bdf4-0800200c9a66
Michael Kotzjan
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votopec
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1 Answers1

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The first two services are Generic Access & Generic Attribute. You can find the UUIDs in the assigned 16-bit numbers document here. Just search for their short version 0x1800 and 0x1801. The other three are not defined in the standard and are custom services defined by the manufacturer.

I searched online for one of the UUIDs and found them in the B24 Telemetry Technical Manual which contains this quick overview (Appendix A):

ID Description Type Format Min Max
a970fd30 Configuration Profile Service - - -
a970fd31 Data Rate Characteristic Uint32 0 10000
a970fd32 Resolution Characteristic Uint8 0 64
a970fd33 Battery Threshold Characteristic Float 2.3 3.5
a970fd34 View PIN Characteristic String 4 4 bytes
a970fd35 Serial Number Characteristic Uint32 Read Only
a970fd36 Data Tag Characteristic Uint16 0 0xFFFF
a970fd37 Battery Value Characteristic Float Read Only
a970fd38 System Zero Characteristic Float -FLT_MAX FLT_MAX
a970fd39 Configuration PIN Characteristic Uint32 0 4294967295
a970fd3a Model Name Characteristic String Read Only
a970fd3b Firmware Version Characteristic Float Read Only
a9712440 Data Profile Service - - -
a9712441 Status Characteristic Uint8 Read Only
a9712442 Data Value Characteristic Float Read Only
a9712443 Data Units Characteristic Uint8 0 255
a9717260 Calibration Profile Service - - -
a9717261 Sensitivity Range Characteristic Uint8 0 3
a9717262 Coefficient (@Index) Characteristic Float -FLT_MAX FLT_MAX
a9717263 Linearisation Index Characteristic Uint8
a9717264 Linearisation Repeat Characteristic Uint8 3 11
a9717265 Linearisation Points Characteristic Uint8 0 15
a9717266 Base Value Characteristic Float Read Only
a9717267 Base Units Characteristic Uint8 Read Only
a9717268 Data Gain Characteristic Float -FLT_MAX FLT_MAX
a9717269 Data Offset Characteristic Float -FLT_MAX FLT_MAX
a971726a Calibration PIN Characteristic Uint32 0 4294967295
a971726b Calibration Units Characteristic Uint8 0 255
a971726c Advanced Index Characteristic Uint8 0 255
a971726d Advanced Data Characteristic Byte Array unknown

You can find even more detailed information for each characteristic in this document as well as a description on how to connect:

  • Scan for devices
  • Select required corresponding device MAC address and connect
  • Send the Configuration PIN to characteristic a970fd39-a0e8-11e6-bdf4-0800200c9a66 attributed to service a970fd30-a0e8-11e6-bdf4-0800200c9a66.
  • Read required aspects and configure as appropriate.
  • Disconnect to allow device to resume transmitting advertising packets
Michael Kotzjan
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  • Thank you. Very detailed answer and a good link to the documentation. It is a B24 device. However, I cannot connect since I don't have the configuration pin of the device, and the default of 0 is not working. I have the key used to add sensor to the official app, but I don't know if it can be converted to 16bit int. ( code is 2x 6 characters - TT0LAC-44HS3Q ). Guess I need to try to get it from the device manufacturers. – votopec Nov 15 '21 at 17:30
  • Glad it is helpful to you! One way of figuring this out would be to analyze the BLE connection using a BLE sniffer or by using your phones log capabilities (Like [this](https://stackoverflow.com/questions/23877761/sniffing-logging-your-own-android-bluetooth-traffic) for example). – Michael Kotzjan Nov 16 '21 at 06:00