[etherlab-users] AL status message 0x0036: "DC Sync0 Cycle Time"

[Jürgen Walter • DATATRONiQ]

Hi Mike,


> I'm attaching the makefile I used. It's the makefile provided by 
> synapticon: ...
cool - many thanks; this will certainly be helpful!!


> Can you answer to any of my questions? :)

>> I wanted to thank you all for your valuable advice. Now I'm acheiving 
>> near 3.5 kHz loop rate without a single datagram loss. My configured 
>> system is (just for reference): Ubuntu 16.04 with kernel 
>> 4.8.15-rt10(preempt_rt patched) and support for native driver. I 
>> would like to ask another question: In the dc_user example I don't 
>> understand why the latency is measured that way. Could someone make 
>> it more clear? This latency is the latency of our application (the 
>> time the scheduler does to put our process to running, so that our 
>> application can process the newly arrived datagram)? What quantity is 
>> measured exactly with this latency? Bonus: Can we measure the time 
>> the datagram does to leave and come back to the master, with 
>> wireshark accurately?

I would love to  -however, only a user myself and not really deep into 
the protocol stack (never even tried debugging the datagrams on the wire 
(debug interface, Wireshark (but I want to!))

I will also share -once I get it all working to good satisfaction also 
share my setup/steps to epiphany. fyi- I am not sure if it is really 
worth doing the entire Xenomai dance - shouldn't latency (on a modern 
and fast enough system (such as your laptop)) mostly be determined by 
the quality of the ethernet driver and of course the chipset? Just 
saying this, because I think the "preempt" seems pretty much standard 
and is really simple to patch and compile.

Thanks!! Jürgen