Parameters relating to service discovery

[Ingolf Petersen]

I have a problem where a central device (iPad) has to connect to a peripheral (running nrf51822, s110) as quickly as possible, receive data and disconnect again.

Right now the connection is fairly quick but the delay between the connection (BLE_GAP_EVT_CONNECTED) and when the central subscribes to the service running on the peripheral (detected via BLE_GATTS_EVT_WRITE) is too long. I'm told by the app developer that there's nothing that can be changed in the app to speed this up. Are there any parameters on the peripheral side that can be tuned to hasten the service discovery and/or subscription?

[Carles]

Hi there,

There are 3 things you can do to speed things up:

1. Bond. If your devices are bonded (on a first connection) then you won't need to do service discovery again anymore, and you will be able to cache the attribute handles on the smartphone app so that you can directly go for the data as soon as you connect

2. Change the connection parameters on the smartphone side. When you create a connection to a peripheral, you are typically allowed to set the connection parameters. The lower the connection interval, the quicker data will be transferred.

3. Request a connection parameter update from the peripheral as soon as the connection is established. This is the same as 2) but initiated from the peripheral. Do this only if 2) is not possible.

Ideally 1) should be used, or a combination of 1) and 2).

Carles

[Ingolf Petersen]

Hi Carles, thanks for a great reply.

Regarding 1), on the nrf side I guess I should then be using the bond manager from the SDK?

Another thing, when the devices enter a bond do they then keep communicating to sync the connection or is it simply so that they can quickly connect without needing to negotiate connection parameters again?

[Carles]

Hi there,

Yes, the bond manager is the easiest option. Please refer to the Bond Manager's documentation for more details on how to use it:

https://devzone.nordicsemi.com/documentation/nrf51/5.1.0/html/a00102.html

A bonding procedure is used to exchange security keys between the 2 devices. Once those keys have been generated and stored in non-volatile memory, every time you reconnect to that device you simply load the keys and use them directly, no need to perform any additional procedures at all. After bonding you can of course remain connected, no issue at all.

[Ingolf Petersen]

Brilliant! Thanks for the info.

[Ankush]

Hi ,

I am trying to open the above link but it saying Not found..Can you please share it once again.