TgForce Impact Running Sensor Andoid API

The TgForceSensor repository contains Android code to interface with the TgForce Impact Running Sensor. The TgForce sensor is a Bluetooth LE device that measures tibial shock. It follows the
Bluetooth LE standards and is relatively easy to interface with.

This repository contains Android code to interface with the device. The protocol is encoded in the source code and is documented belowbelow.

TgForce Impact Running Sensor Protocol

The protocol consists of four standard Bluetooth GATT services and a custom service.

The protocol below is documented as follows, with every xxxxxx-xxxx-xxxx-xxxx-xxxxx representing a UUID:

• xxxxxx-xxxx-xxxx-xxxx-xxxxx Service name
  • xxxxxx-xxxx-xxxx-xxxx-xxxxx Characteristic name
    • xxxxxx-xxxx-xxxx-xxxx-xxxxx Description name

The BlueTooth 4.0 services the device exposes are:

• 00001800-0000-1000-8000-00805f9b34fb Generic Access service
  • 00002a00-0000-1000-8000-00805f9b34fb Device Name
  • 00002a01-0000-1000-8000-00805f9b34fb Appearance
  • 00002a04-0000-1000-8000-00805f9b34fb Peripheral Preferred Connection Parameters
• 00001801-0000-1000-8000-00805f9b34fb Generic attribute service
  • 00002a05-0000-1000-8000-00805f9b34fb Service Changed
    • 00002902-0000-1000-8000-00805f9b34fb Client Characteristic Configuration: notifications / indications
• 0000180a-0000-1000-8000-00805f9b34fb Device Information
  • 00002a29-0000-1000-8000-00805f9b34fb Manufacturer Name String
  • 00002a24-0000-1000-8000-00805f9b34fb Model Number String
  • 00002a25-0000-1000-8000-00805f9b34fb Serial Number String
  • 00002a27-0000-1000-8000-00805f9b34fb Hardware Revision String
  • 00002a26-0000-1000-8000-00805f9b34fb Firmware Revision String
  • 00002a28-0000-1000-8000-00805f9b34fb Software Revision String
• 0000180f-0000-1000-8000-00805f9b34fb Battery Service
  • 00002a19-0000-1000-8000-00805f9b34fb Battery Level (0-100)
    • 00002902-0000-1000-8000-00805f9b34fb Client Characteristic Configuration: notifications / indications
• f6531000-9ce4-450d-b276-3b5a88fa2e73 TgForce Service
  • f6531010-9ce4-450d-b276-3b5a88fa2e73 PPA
    • 00002900-0000-1000-8000-00805f9b34fb Characteristic Extended Properties
    • 00002901-0000-1000-8000-00805f9b34fb Characteristic User Description
    • 00002902-0000-1000-8000-00805f9b34fb Client Characteristic Configuration: notifications / indications
  • f6531011-9ce4-450d-b276-3b5a88fa2e73 gThreshold
    • 00002900-0000-1000-8000-00805f9b34fb
    • 00002901-0000-1000-8000-00805f9b34fb
  • f6531013-9ce4-450d-b276-3b5a88fa2e73 Delay
    • 00002900-0000-1000-8000-00805f9b34fb
    • 00002901-0000-1000-8000-00805f9b34fb
  • f6531014-9ce4-450d-b276-3b5a88fa2e73 Cadence
    • 00002900-0000-1000-8000-00805f9b34fb
    • 00002901-0000-1000-8000-00805f9b34fb
    • 00002902-0000-1000-8000-00805f9b34fb

The last service, the custom TgForce service, is of course the most interesting. It implements the main functionality of the device. To make sense of the data that is returned, some more information is needed about how to convert the returned numbers to values with meaningful units:

• PPA: The PPA is the peak positive acceleration. It represents the size of the peak of downwards acceleration. The signal is sampled at 1600Hz and filtered using a low pass filter of 50Hz. The characteristic uses unsigned integers in the range of [0-255]. The to convert the values to g the following factor is needed: 23.9141g/254, since 23.9g is the maximum acceleration.
• gThreshold: The gThreshold is the minimum acceleration that needs to be exceeded before a peak is considered. It is represented using a value [0-85]. The default is 3.6g. To set the threshold multiply the value in g with 5.32, so the default value is 5.32*3.6g = 19.
• delay: The delay instructs the device to discard superflous peaks for a certain period after a peak is detected. It is assumed that strides take a minimum amount of time: this is encoded as the delay. The default value is 550ms. It is represented using an integer from zero to 19999. To set the delay multiply the value in ms with 17.53. The default value is 550*17.53 = 9642.
• Cadence: The cadence is given as a number of steps pre minute. No conversion is necessary.

Source Code Organization & Developing

The source code is organized following the Android Studio project settings.

License and Credits

This code was developed at University Ghent, IPEM by Joren Six. It is licensed under a BSD License.

Thanks to Kelsec Systems for providing documentation and support via email.

Change Log

01/10/2015 First version