[riot-devel] 6lowpan fragmentation sending too fast

Joakim Nohlgård joakim.nohlgard at eistec.se
Wed Aug 9 17:34:14 CEST 2017

Dear developers,
I have been working on the kw41zrf driver in PR #7107 [1]. However, I
can't get 6lowpan fragmented packets to transmit properly.
It seems the GNRC stack is trying to pass the next fragment to the
netdev driver before the first fragment has finished transmitting over
the air, resulting in the driver rejecting the send request. Is this a
known problem with any other radio drivers or is it my driver doing
something wrong?
Also, the send code in _send_nth_fragment in gnrc_sixlowpan_frag
contains a check of the return value of gnrc_netapi_send [2], but it
seems like my return code is lost somewhere along the way, because I
never see that debug message.

How do I get the 6lo thread to wait until the radio driver is ready to
send the next fragment?

[1]: https://github.com/RIOT-OS/RIOT/pull/7107
[2]: https://github.com/RIOT-OS/RIOT/blob/master/sys/net/gnrc/network_layer/sixlowpan/frag/gnrc_sixlowpan_frag.c#L211

Best regards,
Joakim Nohlgård
Eistec AB

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