[etherlab-users] DC transmission delay w. fibre optic junctions

[Matthieu Bec]

Hello all,

I have an EtherCAT bus using fibre optic junction modules 
(EK1521/EK1501) to access remote I/O. The DC system time transmission 
delay reported by ethercat tool is giving me some odd numbers:

# ethercat slaves -v| egrep transmission
   DC system time transmission delay: 0 ns           // slave 0 - EK1100
   DC system time transmission delay: 574771462 ns   // slave 1 - EK1521
   DC system time transmission delay: 2147484367 ns  // slave 2 - EK1501
   DC system time transmission delay: 2147484512 ns  // ...
   DC system time transmission delay: 2147484657 ns
   DC system time transmission delay: 2147484802 ns
   DC system time transmission delay: 2147485346 ns
   DC system time transmission delay: 2147485486 ns
   DC system time transmission delay: 2147485631 ns
   DC system time transmission delay: 2147485776 ns
   DC system time transmission delay: 2147485921 ns
   DC system time transmission delay: 2147486076 ns
   DC system time transmission delay: 2147487336 ns
   DC system time transmission delay: 2147487476 ns
   DC system time transmission delay: 2147487631 ns
   DC system time transmission delay: 2147488491 ns


The offset values downstream of slave-2 resemble a lot to
   2^31 =  2147483648

I'm wondering it that might point to some signed-ness (or other) issue 
in the DC offset computation in the ethercat master?

The weird offset prevents me to control an EL2252 DC-module programmed 
with time stamp. The device works fine if I don't use the fiber link.

Has anyone encountered or knows how to fix this?
I'm using master stable-1.5

Many thanks -

-- 
Matthieu Bec                GMTO Corp.
cell:  +1 626 354 9367      P.O. Box 90933
phone: +1 626 204 0527      Pasadena, CA 91109-0933