btstack/doc/manual/docs-intro/gatt_services_intro.md

BTstack allows to implement and use GATT Services in a modular way.

To use an already implemented GATT Service Server, you only have to add it to your application's GATT file with:

• #import <service_name.gatt> for .gatt files located in src/ble/gatt-service
• #import "service_name.gatt" for .gatt files located in the same folder as your application's .gatt file.

Each service will have an API at src/ble/gatt-service/service_name_server.h. To activate it, you need to call service_name_init(..).

Please see the .h file for details.