S120 Central Bonding with S110 peripheral

RE: S120 Central Bonding with S110 peripheral

michaeld — Thu, 06 Aug 2015 11:37:48 GMT

Any chance you can share your implementation?

RE: S120 Central Bonding with S110 peripheral

michiel — Thu, 09 Jul 2015 11:20:29 GMT

I saved the service 'parameters' non-persistently without the device manager.

RE: S120 Central Bonding with S110 peripheral

Petter Myhre — Thu, 09 Jul 2015 10:39:03 GMT

Which of my suggestions did you go for? Persistently or not? Device manager or not?

RE: S120 Central Bonding with S110 peripheral

michiel — Thu, 09 Jul 2015 08:13:58 GMT

I implemented your suggestion and it works great. Thank you very much!

RE: S120 Central Bonding with S110 peripheral

michiel — Wed, 08 Jul 2015 13:20:03 GMT

Thanks for your clear information! I will try to implement your suggestions.

RE: S120 Central Bonding with S110 peripheral

Petter Myhre — Wed, 08 Jul 2015 12:18:19 GMT

We don't have any example to store the service context for the client, neither persistently or not, and it is not completely implemented in the device manager. But I'm not sure you need the device manager, since you don't need encryption.

In ble_app_hrs_c the Database Discovery module does service discovery to find the attribute handles for the CCCD and the characterisitic value for hrs and bas. To skip this step you need to store these (persistently or not) on the first connection and then give them to ble_hrs_c and ble_bas_c on subsequent connections.

As Carles mentioned you can also store the handles through the device manager, with dm_application_context_get dm_application_context_set but device manager requires you to store this information together with a bond.

RE: S120 Central Bonding with S110 peripheral

michiel — Wed, 08 Jul 2015 12:14:41 GMT

Thanks for the information. I will give it a try.

RE: S120 Central Bonding with S110 peripheral

Carles — Wed, 08 Jul 2015 11:42:34 GMT

I'm informed of the following:

We don't cache attributes by default
To achieve that yourself, you need to use the Device Manager, in particular the following methods:

dm_application_context_get dm_application_context_set
You then need to store the context of the db_discovery module using get()
And then restore it after connection using set() to avoid rediscovering

If you have trouble implementing this I suggest you open a ticket with Nordic support, they will probably be able to help you further

RE: S120 Central Bonding with S110 peripheral

Carles — Wed, 08 Jul 2015 11:24:40 GMT

That means then that the GATT client module in the SDK is not caching the attributes. Let me ask around and get back to you

RE: S120 Central Bonding with S110 peripheral

michiel — Wed, 08 Jul 2015 11:22:36 GMT

Hello Carles,

Thanks for your reply. However in the 'ble_app_hrs_c' example the 'service_changed' parameter is already set at '0' and the ' attr_tab_size' parameter does not exists for the central side. If I change the gatts_enable_params for the 'ble_app_hrs' example of the peripheral side as described above. Still both services are discovered each time a new connection is made.

With kind regards, Michiel

RE: S120 Central Bonding with S110 peripheral

Carles — Tue, 07 Jul 2015 08:16:53 GMT

Hi there,

If you want to avoid service discovery and you are not going to change the layout of the Attribute Table during the lifetime of the device, the easiest way to do that is to simply disable the Service Changed characteristic in the GATT server devices.

To do that, simply set the option when enabling the BLE functionality:

  ble_enable_params_t en_param;
  en_param.gatts_enable_params.service_changed = 0;
  en_param.gatts_enable_params.attr_tab_size = BLE_GATTS_ATTR_TAB_SIZE_DEFAULT;
  errcode = sd_ble_enable(&en_param);

Then the GATT client devices do not need to perform service discovery after the first connection, since the absence of the Service Changed characteristic indicates that the layout of the server´s attribute table is never going to change. This way you can also disable encryption if you don't need it, saving some time and energy as well.