Service Changed Characteristic example

[QuentinD]

Hello,

Do you have an example that allows you to use the “Service Changed Characteristic” on the server side?

In fact, I saw on the internet that on IOS, we have to use this service so that the phone's cache is reset if we change the device name in real time.
In my application, the device advertises by default with a default name but the user can change it (when connected via BLE). The problem I have (only on IOS) is that this new name is not updated in the phone scan.

I use the nRF Connect SDK V2.5.0.

Thank you

[Sigurd]

Hi!

I'm not aware of any examples, but it should not be very complicated. Make sure that you have CONFIG_BT_GATT_SERVICE_CHANGED set to y

[QuentinD]

Hi

Yes CONFIG_BT_GATT_SERVICE_CHANGED=y

In the nrf_connect app, I set the Generic Attribute / Service Changed" to the value "Indications enabled". Then, I modify the "Device name" but I do not receive any notification telling me that there has been a modification of the Device name : do you know why ?

[QuentinD]

Is there a function I need to call when I change the device name?

[Sigurd]

QuentinD said:

Is there a function I need to call when I change the device name?

You changed the name with bt_set_name(), or CONFIG_BT_DEVICE_NAME in prj.conf?

Note that the Service Changed Characteristic is used to indicate to connected devices that services have changed (i.e., added, removed or modified).
A change to a characteristic value is not considered a modification of the service.

[QuentinD]

Sigurd said:

You changed the name with bt_set_name(), or CONFIG_BT_DEVICE_NAME in prj.conf?

Both: I put a value in CONFIG_BT_DEVICE_NAME to have a default value but if the user wants to change the device name, I call the bt_set_name() function.

Sigurd said:

A change to a characteristic value is not considered a modification of the service.

Yes I know. The goal would be to use this service to refresh the cache of the IOS phone (I don't know if it works but as I saw on the internet that doing like that would solve my problem. So I would like to be able to do the test).

[Sigurd]

Hi!,

The Bluetooth Host in Zephyr does not expose a API for this, but handles it itself if it sees changes in the services.

As an experiment, you could try to expose the sc_indicate() function. Other users seems to have had success with that:

 RE: Force GATT client to sync database with Zephyr