Advertisement packet loss in Coded PHY vs 1 Mb PHY

[Kcecil]

Using the following:

Rigado BMD-360 nRF52811 development board.

Softdevice S140 7.0.1

SDK 16.0

Using two development boards inches apart, one development board sends a single advertising event every 12 seconds.  The other development board is continuously scanning (interval and window = 7s).  The packets have 30 bytes of data including a sequence number.  I calculated packet loss based on the missing sequence numbers.

Sending and scanning using the 1 MB/s PHY, in a test of approx. 20 minutes  I get 100% reception of packets.

Sending and scanning using the Coded PHY, in the same test I get ~43% reception of packets, ~57% packet loss.

Is this expected behavior, or could I be configuring something wrong when advertising using Coded PHY?

Another behavior I've seen is for the above condition using the Coded PHY to have a repeating pattern of receiving 3 and missing 2.

[Simonr]

Hi Kurtis

Thank you for the update. Can you provide some more details regarding your test setup? What kind of environment are you performing these tests in? What pins on the nRF52811 are you using for SPI communication, and what pins on the UBlox BMD-360 are you using for UART? 

Seeing as the packet loss is now only seen on your custom board, I think we might have a hardware issue on our hands, as it might be that the custom board's antenna is not tuned optimally. If you'd like we can do a review of your schematics and HW layout for you, but I suggest you create a new (private) ticket for that, so we can keep this one public. This is entirely up to you though, and if you'd like, we can keep it in this ticket as well, and I'll set this one to Private mode if you prefer that.

Best regards,

Simon

[Kcecil]

Simon,

It looks like the dropped packets are due to the scan interval/window.  I'm seeing a loss rate of ~15% with interval/window = 10.24s, 4% with interval/window = 7s, 0% with interval/window = 3.125.

[Simonr]

Does this apply to both the custom board and the UBlox BMD-360? It might be that the buffer fills up before the SPI/UART is able to pass it on on longer scan intervals, or are you positive that the data is lost on air?

Does this central application switch between scanning or advertising? If so, it might be that the longer scan intervals/windows are interfered by the device advertising (or trying to).

Best regards,

Simon

[Kcecil]

I haven't had a chance to test the longer interval on the dev board, but I did verify that it was being lost on air and not in the SPI.

In this application the central only scans and for this testing was only scanning the coded PHY.