Beacon advertising and scanning inconsistent

[Jacques]

Hi,

I've developed firmware for nRF52832 to beacon and scan for identical beacons. So with many devices, each can detect the others. What I've noticed is that while most devices detect most beacons, 2 devices might 'synchronize' and miss most of each other's beacons. This happens randomly, and changes when a device is reset. I've played with the advertising and scanning parameters, but I can't avoid it, even when scanning at 100% duty cycle (scan window = scan interval).

my starting parameters are:

Advertising interval 25ms

Scan interval 100ms

Scan window 50ms

In the worst case, it can take up to 2 seconds to detect a beacon.

Any advice is welcome

[Simonr]

Hi

There might be multiple reasons for this inconsistency, but here is one possible cause. This is just based on the information provided and the first thing that came to mind.

In the BLE specification, it is required to add a random delay of 0-10 ms to your requested advertising interval. This is added in the link layer in the SoftDevice, and the application has no control of this delay. By increasing the advertising intervals or scan windows you should be able to mitigate this, but there's no way (in the BLE spec.) to remove this random delay.

Best regards,

Simon

[Jacques]

Thanks Simon,

The random delay is definitely not something I would want to remove. Making smaller scanning windows and intervals seems to improve things. I think that this is because the scanner is switching between the 3 advertising channels more frequently (?)