ESB link in PRX mode requires re-initialization after minutes with nRF54L15

[galenchurch]

We are experiencing some ESB link failures on the receiver end of our system: nrf54L15.  After minutes to hours of use the receiver will stop getting data (we know the transmitter is still sending).  If we re-initialize esb subsystem everything is back to normal.  Unfortunately we have no good means to detect the link is down or know why. Its still in ESB_MODE_PRX we just are no longer getting any interrupts.  We have some timeouts on the configured `event_handler` but those are too long to be very useful.  Any advice you have to debug would be helpful but I also have two questions:

1. Is there some detailed documentation on how the ESB system/driver works on the nRF54L15? the driver code is difficult to understand on its own: https://github.com/nrfconnect/sdk-nrf/blob/main/subsys/esb/esb.c and the documentation page seems generic and high level (does not explain much of what the driver does): https://docs.nordicsemi.com/bundle/ncs-2.7.99-cs2/page/nrf/protocols/esb/index.html
2. Can you provide some ESB status register we might be able to monitor/read from to get more information beyond the three interrupt events and the mode that the ESB is in?

Thanks,

Galen

[Johnny Nguyen]

an update:
after leaving it running for hours on revB and NCS 2.8.0, I was seeing the PRX stuck lockup requiring a reset. I slowed down the ESB communication frequency and it did not lock up during extended time testing.

As an extra datapoint, I tested latest 54L15 on NCS 3.0.0 and was not able to replicate the failure, even at maximum transmission rate. I am still leaving this test running to see if it comes up.

Any reason you are locked on v2.8.0 and revA chips?

[galenchurch]

That's good to hear you can re-produce. I can speak with the team if reducing the comm frequency is possible.  What freq did you find worked well? 

We have RevA on our current custom boards and cannot replace until our next boards are built.  It would be great to know if this will be a problem for latest versions (Rev1 or Rev2?)... i appreciate your continued testing.