[etherlab-dev] Datagram SKIPPED x Times

[Mike O'Connor]

Hi All

I have been testing with Etherlab and a small number of Beckhoff Digital
IO, the Ethercat (not Etherlab) technical data seems to indicate that an
updates at a rate of at least 30 micro seconds for up to 1000 IO points
(possibly faster for smaller numbers) is possible.

I adjusted the user land examples to work with our IO and then started
increasing the frequency and found that at 4K I get no issue (maybe a
couple of the dmesg messages below at the start)

[  412.872048] EtherCAT WARNING: Datagram f6bbfc00 (domain0-0) was
SKIPPED 6 times.

but as I increase the rate to 8K then 12K and finally 25K the number of
SKIPPED gets larger and larger

[173178.785515] EtherCAT WARNING: Datagram f6851360 (domain0-0) was
SKIPPED 43476 times.

I did adjust the intel GigE driver (e1000e) to use a
InterruptThrottleRate of 0 which helped a lot with consistency. I also
tried the non generic drive with no change in the above messages.

I've confirmed via a mirror port on a switch and a capture of the
packets that the IO is replying to every packet we send and that the
rate of sending would seem to match the 8K, 12K, and 25K.

This seems to indicate to me that the issue is in the Ethercat master,
is etherlab up to the task of running a high scan rate ?

Thanks
Mike