Zephyr OS, boards with different performance and 6LoWPAN frame retransmission

[ValNyrov]

Hello OpenThread community!

My hardware configuration is:

1)One board nRF52840-DK acting as router and commissioner,OS Zephyr 3.3.99,chip speed 64 MHz
2)One board TI CC2652-launchpad, acting as minimal end divice and joiner,OS Zephyr 3.3.99,chip speed 48 MHz
3)Packet sniffer: Wireshark + nrf52840-dongle

In general, everything works and the commissioning process is completed.
But I noticed in the log of the nRF52840-DK board that in the commissioning process there are repetitions of sending some frames, it is highlighted in the screenshot with a red line. This is also visible in the wireshark log (lines 33-50).

Screenshot TI CC2652 log:

Full logs in attachment.

After the completion of the commissioning, I execute the ping command whith 1024 bytes on the side of the nRF52840-DK board, and there are also retries of transmission of some frames.

Since these boards have different chips with different speeds, I assume that the CC2652 board does not always have time to process a frame (this is just my guess).

Perhaps I should correctly set the timeouts for waiting ACK frame from CC2652-launchpad and increase the time between retransmissions of frames? Please tell me how to do it right.

Zephyr logs:
nRF52840.log
ti_cc2652.log

Wireshark:
wireshark.pcapng.tar.gz

What commands in Zephyr did I execute:
zephyr_commands_nRF52840.txt
zephyr_commands_ti_CC2652.txt

Best Regards,
Valeriy

[jwhui]

Looking at the pcap file, it does appear that many packets sent from nRF52840 to CC2652 do not have a corresponding ack message. I would suggest reaching out to TI for support on this.

[ValNyrov]

Thanks for the answer. What timeout value should be for corresponding ack message? Is the timeout value set in the driver or in the OpenThread code?

Best Regards,
Valeriy

[jwhui]

In the case of nRF52840, the ACK timeout is implemented in the radio driver.

However, the packet capture does not show ACKs being sent by CC2652 in many cases, so I don't think this is a timeout configuration issue.

[ValNyrov]

Thanks for the help Jonathan!

I decided to check how two nrf52840 boards will behave, one board is configured as FTD and the other as MTD.
Both boards are on my table at a distance of 50cm from each other, the signal level is about -45 dBm.
On the first board (FTD), I launched a ping (20 packets of 1024 bytes of data), and also saw in the logs that not all requests have a corresponding ack message. Is it normal that there are not always ack messages? Maybe something else needs to be configured?

wireshark:
wireshark.pcapng.gz

Zephyr logs:
nRF52840_FTD.txt
nRF52840_MTD.txt

Best Regards,
Valeriy

[maciejbaczmanski]

Hi @ValNyrov.
How do you build SW for nRF52840?
If you are using nRF Connect SDK, could you provide tag / commit sha used while building?
Also are you using any custom configuration for samples?

Best Regards,
Maciej