[etherlab-users] Sync problems and DC mode

[Graeme Foot]

As Boris says, master->app_time needs to actually match your PC's time (converted to your app's timeframe).

Another change you could try is as below.  From line 1115:

  // send process data
  rtapi_mutex_get(&master->mutex);

  // queue domain data
  ecrt_domain_queue(master->domain);

  // update application time
  master->app_time = rt_get_app_time();
  ecrt_master_application_time(master->master, master->app_time);

  // sync ref clock to master
  ecrt_master_sync_reference_clock(master->master);

  // sync slaves to ref clock
  ecrt_master_sync_slave_clocks(master->master);

  // send domain data
  ecrt_master_send(master->master);
  rtapi_mutex_give(&master->mutex);


You want as constant a time between calling ecrt_master_application_time() and ecrt_master_send() as possible.  The calls to ecrt_domain_queue() call takes variable amounts of processing time, so do that first.  Also call ecrt_master_sync_reference_clock() every cycle to ensure the reference slave gets lot of small updates rather than a few big updates.  This helps all slaves keep sync better.  It also avoids another source of variable processing time between ecrt_master_application_time() and ecrt_master_send().


Graeme.


-----Original Message-----
From: etherlab-users [mailto:etherlab-users-bounces at etherlab.org] On Behalf Of Boris Skegin
Sent: Tuesday, 23 January 2018 2:07 p.m.
To: etherlab-users at etherlab.org; Ignacio Rosales Gonzalez <narogon at gmail.com>
Subject: Re: [etherlab-users] Sync problems and DC mode

Hello.

> With this version
> <https://github.com/narogon/linuxcnc-ethercat/commit/e4ab86ba6167ced53
> 2e49904059df580062b2d97#diff-059a684a933530837771b5a249433ff3>
> (also as attachment lcec_main.c) I get the servos sync and OP but it 
> seems that the PDO doesn't arrive for some of the slaves (no idea why).

master->app_time += master->app_time_period;  means that you just sum
up constant cycle times of  the LinuxCNC thread. So any latency information gets lost here.

Rather  make  master->app_time  be equal to something like
rt_get_time() transferred to EtherCAT time.

I also think that a proper value for sync0Shift  can help a lot.

If however nothing of that helps, then proceed  to  Graeme Foot's option b) .

BTW, what exactly is your kernel and network card and do you really use an adopted ( non-generic) network driver?

Regards,
boris
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