add/remove GATT service or characts with bonded device

[jfDEVmoto]

Hello, I asked a question after this old one : old one and I read other posts on the subject.

I wonder whether explained constraints may have changed or not since I am using SD130 2.0 - SDK11- nRF51422.

My point is that I want my GATT server to create some services only after some app level transaction has passed. For this purpose, I create a transaction service so that a bonded peripheral can play with. Then after the event has occured, I trigger the creation of another applicative Gatt service. ideally, I want all this to be visible only after bonding, that is done with a static passphrase.

My experience is that when my peripheral app () is bonded to a central (Android), If I update my app with new services or remove services and flash the peripheral, my central still sees the same set of services and chars. This is quite annoying. I assumed at first that this would be because the Gatt table would be static in flash within the soft device for a given bond. but then I tried to flash the softdevice itself and I discovered that my Android central still connected and discovered the old set of services. I guess that whatever, if my app changes while GATT table has not, it might crash quite soon when the peripheral wants to access some supervised data. So I have to reset the bond when I change my services set.

• is it possible to do it without giving up the bond ? (I don't want to disturb user with this static key too often) I guess this is on the android side... but maybe this behavior is linked to some bonding parameter that is set on the peripheral GATT server.

• I use device manager, would the behavior be different with peer manager ?

Thanks for your help

[jfDEVmoto]

I have to check something like that... stackoverflow.com/.../how-to-programmatically-force-bluetooth-low-energy-service-discovery-on-android

[jfDEVmoto]

and this :code.google.com/.../detail It looks like the generic attribute service may implement a service changed characteristic to help bonded central to refresh its cache. !!!

[FormerMember]

As @jfDEVmoto says, service changed should be used indicate to the client that one or more services has been changed.

When bonding to a device, the client will typically cache the services on the server side. It will therefore not normally do a service discovery upon a re-connection. When the client and server devices are bonded, and the server has changed one or more services, the service changed indication should be transmitted upon a re-connection, and the client should perform a service discovery procedure.

Service changed is described in the Bluetooth Core Specification v. 4.2, Vol 3, Part G, chapter 7.1.

[jfDEVmoto]

Thanks, I am trying to implement this so I might have further questions on this topic in the future. Today, my concern is about the flash memory. When I indicate the service change in order to force the client to refresh services discovery with bonded device, will this trigger flash memory update on the server side using device manager ? I am concerned about this because my device should have a quite long life and quality of service that might lead to a high number of such refreshes, aproaching flash memory max cycle life.

[FormerMember]

To make sure that the allocated flash area never gets full, you can make sure to delete old instances after the service changed.