Using Google Fast Pair with the nRF Connect SDK

Integrating Fast Pair
Provisioning the device
- Registering Fast Pair Provider
- Provisioning registration data onto device
Setting up Bluetooth LE advertising
Setting up GATT service

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:

Provisioning the device
Setting up Bluetooth LE advertising
Setting up GATT service

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 format 0xXXXXXX,
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 Seeker must also know the Provider’s transmit power to determine proximity.

Advertising data and parameters 

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. Special battery data can be included in not discoverable advertising packet using the Fast Pair Battery Notification extension. To use this extension, you have to:

Call bt_fast_pair_battery_set() to provide battery information.
Set bt_fast_pair_adv_config.adv_battery_mode to either BT_FAST_PAIR_ADV_BATTERY_MODE_SHOW_UI_IND or BT_FAST_PAIR_ADV_BATTERY_MODE_HIDE_UI_IND to include the battery notification in the generated advertising payload.

See the Fast Pair Battery Notification extension documentation for more details about this extension.

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.

Fast Pair advertising data provider 

The Fast Pair advertising data provider (CONFIG_BT_ADV_PROV_FAST_PAIR) can be used to manage the Fast Pair advertising data. See Bluetooth: Fast Pair for an example of using the provider in a sample. See subsys/bluetooth/adv_prov/providers/fast_pair.c for provider implementation.

Advertising TX power 

The Fast Pair Seeker must know the TX power of the Provider to determine proximity. The TX power can be provided in one of the following ways:

Defined during model registration
Included in the advertising payload

See the Fast Pair TX power documentation for more information.

Advertising data provider

If your application uses Bluetooth LE advertising providers, you can use the TX power advertising data provider (CONFIG_BT_ADV_PROV_TX_POWER) to read the advertising TX power from Bluetooth controller and add it to the generated advertising data. The CONFIG_BT_ADV_PROV_TX_POWER_CORRECTION_VAL option can be used to define a TX power correction value that is added to the TX power readout included in the advertising data. The option can be used to take into account hardware configuration, for example, used antenna and device casing. See Bluetooth: Fast Pair sample for an example of how to use the TX power advertising provider.

Multiprotocol Service Layer front-end module (MPSL FEM)

If your application uses MPSL Front-end module feature, you can use a front-end module power model. The power model allows you to control the TX power more accurately and compensate, for example, for external conditions. See the TX power split using models section of the Front-end module feature documentation for more details. See the MPSL FEM power model section in API documentation for API documentation.

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.