[etherlab-users] DC-Synchronization - Sync signal generation

[Gavin Lambert]

Hi Jun,

 

Thanks; I’m having a look at it, but much of it is new to me.  I’m using PREEMPT_RT so my code is based on the dc_user example, not the RTAI examples, and I’d probably have to try adapting it before I could test it.

 

Regards,

Gavin Lambert

 

From: Jun Yuan [mailto:j.yuan at rtleaders.com] 
Sent: Friday, 4 April 2014 01:46
To: Gavin Lambert
Cc: etherlab-users at etherlab.org
Subject: Re: [etherlab-users] DC-Synchronization - Sync signal generation

 

Hi Gavin,

your interest is my motivation. I have attached the bundle file. 

My changes is base on the newest Version 1.5.2 in 'stable-1.5' branch. I added a new 'rtleaders' branch first and did all my changes on that. So after "$ hg unbundle etherlab_1.5.2_jyuan.hg", don't forget to switch to the 'rtleaders' branch using "$ hg update rtleaders".

I found a better way of synchronizing the master clock to ref slave clock. It is much faster and more stable. I managed to port my C++ code into C code in the rtai_rtdm_dc example today, but I cannot test if the new code compiles right now. If you have a rtai environment, please test it for me if it compiles, and give me some feedback. 

Besides that, there is a more accurate DC time offset calculation. There should be no more errors like "Slave did not sync after 5000ms". The accurate time offset estimation saves much time for the DC Sync procedure.  Slaves would have such a small dc diff (several hundred ns maybe) at the beginning of the dc sync check, that I even changed EC_SYSTEM_TIME_TOLERANCE_NS from 1000000ns to 1000ns.

The postponed check of master->has_app_time makes the error "No app_time received up to now, but master already active" away.

And there are the bugfix for ecrt_master_select_reference_clock() from Graeme Foot, and some other bug fixes from Jeroen Van den Keybus.

 

Any feedback is welcome. Have fun testing those changes!

 

Jun

 

On Thu, Apr 3, 2014 at 12:13 AM, Gavin Lambert <gavinl at compacsort.com> wrote:

On 2 April 2014 22:40, quoth Jun Yuan:

> But there is a reason why we all put the ecrt_master_application_time() outside
> the loop. Because we all got burned by the error "No app_time received up to
> now, but master already active.", which is a timing bug in Etherlab. I've
> resolved the problem by change the code of Etherlabmaster, which get rid of
> the "No app_time" bug. Now I don't need to call ecrt_master_application_time()
> outside the loop any more. I will publish the bundle to the mailing list when
> I have time.

I'd be very interested to see this.  Slave sync timing, "no app time", and the 5000ms sync timeout have been a recurring bugbear for me.

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