BLE Protocol Packets and Timing

[grantcox]

Hi,

I'm looking into the reliability of the BLE connection from one nrf52 to another nrf52. I'm looking to understand a few things.

1. Once a connection is established over BLE using the nordic SDK, how is the connection maintained? How often (time wise) does the software check that the paired bluetooth device is still communicating/connected with the local host? How large are those packets, and how many are sent?
2. With the LED Button service, if I trigger an event by pushing and holding a button, is an event continuously sent to the paired device, or is there a start and stop signal transferred over bluetooth? What is the button service packet size?

Thank you for any help. I want to understand the reliability of BLE in my applications.

Best,

Grant

[natersoz]

I highly recommend this book:

Bluetooth Low Energy: The Developer's Handbook

by Robin Heydon.

That is a very broad question and the answers can be found in this book in the BT specification itself (thought much harder to read).

[grantcox]

Okay, I'm looking at the book now. For simplicity, I'm building off of the ble_app_blinky example for my project. Do you have any insight into that specific example?

[natersoz]

No - other than it uses the softdevice.

Here is a link to a short paper on connect intervals that can help you quickly determine data throughput.

http://www.rigado.com/?wpdmdl=1312

As to robustness, it comes down to signal to noise and 'connection timeout interval'.

[grantcox]

Okay. Thank you very much!