Using Google Fast Pair with the nRF Connect SDK
Google Fast Pair is a standard for pairing Bluetooth® and Bluetooth Low Energy (LE) devices with as little user interaction required as possible. Google also provides additional features built upon the Fast Pair standard. For detailed information about supported functionalities, see the official Fast Pair documentation.
Note
The Fast Pair support in the nRF Connect SDK is experimental. The implementation is not yet ready for production and extensions are not supported.
The implementation does not pass end-to-end integration tests in the Fast Pair Validator. The procedure triggered in Android settings is successful (tested with Android 10).
Integrating Fast Pair
The Fast Pair standard integration in the nRF Connect SDK consists of the following steps:
These steps are described in the following sections.
The Fast Pair standard implementation in the nRF Connect SDK integrates Fast Pair Provider, one of the available Fast Pair roles. For an integration example, see the Bluetooth: Fast Pair sample.
Provisioning the device
A device model must be registered with Google to work as a Fast Pair Provider. The data is used for procedures defined by the Fast Pair standard.
Registering Fast Pair Provider
See the official Fast Pair Model Registration documentation for information how to register the device and obtain the Model ID and Anti-Spoofing Public/Private Key pair.
Provisioning registration data onto device
The Fast Pair standard requires provisioning the device with Model ID and Anti-Spoofing Private Key obtained during device model registration. In the nRF Connect SDK, the provisioning data is generated as a hexadecimal file using the Fast Pair provision script.
If Fast Pair is enabled with the CONFIG_BT_FAST_PAIR Kconfig option, the Fast Pair provision script is called automatically by the build system and the resulting hexadecimal file is automatically added to the firmware (that is, to the merged.hex file).
You must provide the following CMake options:
FP_MODEL_ID- Fast Pair Model ID in format0xXXXXXX,FP_ANTI_SPOOFING_KEY- base64-encoded Fast Pair Anti-Spoofing Private Key.
The bt_fast_pair partition address is provided automatically by the build system.
For example, when building an application with the nRF Connect for VS Code extension, you need to add the following parameters in the Extra CMake arguments field on the Add Build Configuration view: -DFP_MODEL_ID=0xFFFFFF -DFP_ANTI_SPOOFING_KEY=AbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbA=.
Make sure to replace 0xFFFFFF and AbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbAbA= with values obtained for your device.
See Providing CMake options for more information about defining CMake options.
Setting up Bluetooth LE advertising
The Fast Pair Provider must include Fast Pair service advertising data in the advertising payload. The Fast Pair service implementation provides API to generate the advertising data for both discoverable and not discoverable advertising:
bt_fast_pair_adv_data_size(),bt_fast_pair_adv_data_fill()These functions are used to check the buffer size required for the advertising data and fill the buffer with data. Managing memory used for the advertising packets is a responsibility of the application. Make sure that these functions are called by the application from the cooperative context to ensure that not discoverable advertising data generation is not preempted by an Account Key write operation from a connected Fast Pair Seeker. Account Keys are used to generate not discoverable advertising data.
bt_fast_pair_set_pairing_mode()This function is to be used to set pairing mode before the advertising is started.
Since you control the advertising, make sure to use advertising parameters consistent with the specification. The Bluetooth privacy is selected by the Fast Pair service, but you must make sure that the following requirements are met:
The Resolvable Private Address (RPA) rotation is synchronized with the advertising payload update during the not discoverable advertising.
The Resolvable Private Address (RPA) address is not rotated during discoverable advertising session.
See the official Fast Pair Advertising documentation for detailed information about the requirements related to discoverable and not discoverable advertising.
See samples/bluetooth/peripheral_fast_pair/src/bt_adv_helper.c for an example of the implementation.
Setting up GATT service
The Fast Pair GATT service is implemented by the Google Fast Pair Service (GFPS). The service implements functionalities required by the Fast Pair Procedure. The procedure is initiated by the Fast Pair Seeker after Bluetooth LE connection is established. No application interaction is required.
The Fast Pair GATT service modifies default values of related Kconfig options to follow Fast Pair requirements. The service also enables the needed functionalities using Kconfig select statement. For details, see the Google Fast Pair Service (GFPS) Bluetooth service documentation in the nRF Connect SDK.