BLE GATT Queue module can be used to buffer BLE GATT requests if SoftDevice is not able to handle them at the moment. In this case, processing of queued request is postponed. Later on, when corresponding BLE event indicates that SoftDevice may be free, the request is retried. This module can be used in multiple connection scenario.
Module currently can handle following types of GATT request:
- Read Characteristic or Descriptor (See sd_ble_gattc_read)
- Write Characteristic Value or Descriptor (See sd_ble_gattc_write)
- Primary Service Discovery (See sd_ble_gattc_primary_services_discover)
- Characteristic Discovery (See sd_ble_gattc_characteristics_discover)
- Descriptor Discovery (See sd_ble_gattc_descriptors_discover)
- Notify or Indicate an attribute value. (See sd_ble_gatts_hvx)
For API documentation of this module, refer to BLE GATT Queue.
This module uses the Queue library module to implement BLE Request queue for each registered connection and Memory Object module to allocate data associated with request descriptors.
BLE GATT Queue can be used with BLE service clients and other BLE modules that issue GATT requests to the SoftDevice. The following BLE service clients show the usage of this module: Battery Service Client, Device Information Service Client, Heart Rate Service Client and Running Speed and Cadence Service Client.
Message Sequence Charts
The following chart shows how to use this module together with a BLE service client to handle events from the SoftDevice. The Device Information Service Client is used in the chart below as an example.
