RE: BLE data loss with nus

eleven-x_devteam — Wed, 27 Nov 2024 20:43:25 GMT

Hi Vidar,

Thanks for the reply! It was a great clue to help me start debugging.

I’ve checked the BLE data transmission (TX) and reception (RX) on both the peripherals and the central device, and they are working perfectly.

I discovered a race condition in our custom code during BLE data processing, which occurs when the central receives multiple data packets from the peripherals. I’ve fixed the issue.

Thank you again!

RE: BLE data loss with nus

Vidar Berg — Tue, 26 Nov 2024 15:02:20 GMT

Hi,

I think the data loss must occur somewhere between receiving the sensor measurement value and the BLE send function (assuming the send function always returns with NRF_SUCCESS). Data that is successfully added to the SoftDevice output queue will be sent to the receiver. If the packet fails to be sent after x retransmissions, the Softdevice will terminate the link as required by the specification.

[quote user=""]I've observed occasional data loss at the central device, even though the peripherals seem to send data without errors.[/quote]

A notification or indication packet added to the output queue with sd_ble_gatts_hvx() will be added to the output queue if the return value is NRF_SUCCESS. Does your application verify the return code of this function to detect when a packet failed to be added to the queue?

[quote user=""]Is it possible for data loss to happen when two data packets arrive simultaneously at the central device?[/quote]

This should not happen, and I do not recall seeing any reports of this being a problem.

Best regards,

Vidar