@Joseph: According to the spec of ANCS" the NC (notification consumer) should look for and subscribe to the Service Changed characteristic of the GATT service in order to monitor for the potential publishing and unpublishing of the ANCS at any time."
What it means is the client should enable indication on the service changed characteristic. And it will receive an indication (BLE_GATTC_EVT_HVX event) when there's a service change.
@Joseph: According to the spec of ANCS" the NC (notification consumer) should look for and subscribe to the Service Changed characteristic of the GATT service in order to monitor for the potential publishing and unpublishing of the ANCS at any time."
What it means is the client should enable indication on the service changed characteristic. And it will receive an indication (BLE_GATTC_EVT_HVX event) when there's a service change.
Hello Hung, I downloaded the ble_app_ancs project (SDK v8.1.0), I search through the 2 files main.c & ble_ancs_c.c with the matching word "change", but I cannot find anything related to service change of the gatt server, could you give me some hints? Thanks!
@Joseph: I'm sorry for misleading you. The spec tells the NC "should" not "shall" so it's optional. I edited my answer.
In our example, unfortunatelly, we don't subsrcribe to service changed indication but to a service discovery every time we get connected. If we don't see the ANCS service we will disconnect.
I guess this something you would need to implement on your own, to enable service change CCCD, and wait for the indication event to do either a disconnect and reconnect, or another service discovery.
Another option is to add a timer and do service discovery to look for ANCS to be available for several time, and disconnect after a timeout.
Hello Hung, thank you for your suggestions.
If we want to subscribe to the service changed indication, the first step is to use the function sd_ble_gattc_primary_services_discover() to search for the Generic Attribute (0x1801), is that correct? Thanks!
