[etherlab-users] Ethercat master kernel module warnings

[John Hubbard]

Hello,

I'm working on a proof of concept application using the IgH EtherCAT 
master however I'm having some problems.  Specifically I'm seeing 
unmatched and skipped datagram packet warnings coming out of the kernel 
module:
====================================================
Dec 11 13:26:31 lyot kernel: [878188.716201] EtherCAT WARNING: Datagram 
ffff88032e383558 (domain0-0-main) was SKIPPED 21 times.
Dec 11 13:26:31 lyot kernel: [878189.443671] EtherCAT WARNING 0: 20 
datagrams UNMATCHED!
Dec 11 13:26:32 lyot kernel: [878189.769889] EtherCAT WARNING: Datagram 
ffff88032e383558 (domain0-0-main) was SKIPPED 21 times.
Dec 11 13:26:32 lyot kernel: [878190.444575] EtherCAT WARNING 0: 20 
datagrams UNMATCHED!
====================================================
Based on the mailing list and the documentation PDF I believe that the 
problem is related to attempting to run the cyclic task too quickly.  
I'm running the cyclic task in userland at ~20Hz (50ms delays) on Ubuntu 
14.04 with the 3.16.0-55 kernel. The master is relying on the generic 
NIC driver to control a 4 port Intel 85271EB PCIe card.  Even slowing 
way down to 5 seconds I still see the occasional "SKIPPED 1 times" 
message.  The manual suggests that the theoretical cyclic rate should be 
many orders of magnitude faster.  I realize that the theoretical rate is 
theoretical, but I would have hoped a cyclic task of 20Hz~200Hz to be 
achievable with the generic NIC driver.

In short my application (after setting up the master and domain) is doing:

    ecrt_master_receive
    ecrt_domain_process
    // read process data
    // calculations
    // write process data
    ecrt_domain_queue
    ecrt_master_send


So my question are:
Has anyone else seen similar problems with unmatched/skipped datagrams 
even at very low cyclic task rates?
What sort of frequencies should I expect on a non rt-kernel, with a 
userland app, and the generic NIC driver?
Does anything look obviously wrong with my attached code?  (Be gentle 
I'm primarily a non real time Java programmer).

In case it helps my end goal is to replace the discontinued Spectracom 
TSync PCIe PTP DIO card with a 'block' of Beckhoff modules that provide 
the same input timestamping, and output match time functionality. I'm 
currently working with an EK1100 (EtherCat coupler), EL1252 (24v input 
w/time stamp), EL2252 (24v output w/time stamp), and an EL6688 (PTP 
module).  When all done everything will be controlled by a userland app 
running on a CentOS 7 system with standard RHEL/CentOS 7 kernel.  At 
this point I'm still just trying to familiarize myself with the API and 
get a basic proof of concept application running.

I have been partly successful reading the input states, and 
rising/falling latch times from the EL1252.  I have not yet had success 
with the output module EL2252.  I'll put out another email asking for 
help with that one.  I haven't even tried to work with the EL6688 module.


Thanks in advance


-- 
-john

To be or not to be, that is the question
                 2b || !2b
(0b10)*(0b1100010) || !(0b10)*(0b1100010)
         0b11000100 || !0b11000100
         0b11000100 ||  0b00111011
                0b11111111
255, that is the answer.

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