[riot-devel] Counting retransmissions on at86rf2xx

Oleg Hahm oliver.hahm at inria.fr
Wed Feb 10 11:48:17 CET 2016

Hi Andreas!

On Wed, Feb 10, 2016 at 10:21:09AM +0100, Andreas Weigel wrote:
> if there is no code available, wouldn't it be rather easy to introduce a
> simple intermediate layer, set the number of retransmissions in the driver
> to 0, and re-initiate the transmission every time the driver reports a
> failure (up to the desired number of retransmissions) and count the
> retransmissions there? You probably loose some microseconds compared to the
> hardware solution, but gain the information you need.

Yes, that's indeed the solution we discussed some time ago. Unfortunately,
it's a bit more complicated than that since the transceiver would not pass
link-layer ACKs up to software in extended mode and in basic mode the driver
has to perform the address checks in software, too. So, all in all, it is
doable, but requires some work and it's not 100% clear how much overhead it
actually generates.

However, Thomas Eichinger is already working on that and has completed the
driver rework. (Thanks for that!)  Hence, I was checking if the link-layer
part (handling ACKs and taking care of retransmissions) might be already
available in some other pieces of code.
> PS: As you are speaking of multi-hop traffic, I'd like to use the
> opportunity to bring attention to the "deafness"-problem again, which may
> impact performance using the extended operating mode in combination with
> multi-hop traffic. (mailing list topic: at86rf2xx radio driver -- potential
> severe performance issues for multi-hop communication)

Thanks for the reminder. So far I didn't experienced any severe performance
problems, but maybe I should take a closer look.

/* Thanks to Rob `CmdrTaco' Malda for not influencing this code in any
 * way.
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