Re: Freqmod test result & Q

[Paul <paul.corner-at-tesco.net>]

Hi Chris

There are three realtime tasks within freqmod where jitter may be expected -

The first is the pulse timing loop as defined by PERIOD.
The second is set by CYCLE_TIME in TRAJ, typically 10mSec.
The third is also CYCLE_TIME, but this time in the AXIS_n section. (Side 
note: From reading emcmot.c, it would appear that only the parameter in the 
last AXIS_n has any effect)

The interrupt latency that you have recorded by running the 
rtai/testing/testsuite will affect the timing all three of the above tasks in 
freqmod. It would be interesting to hear what sort of period you see the 
"algorithmic jitter".

Regards, Paul.


On Sunday 30 Jun 2002 5:02 pm, Chris Wagner wrote:
> There is a third type of jitter - the algorithmic jitter (both freqmod
> and steppermod have this effect, perhaps it is easier to tune
> steppermod?).  This jitter is at a longer period then the real-time
> timers and interrupt latency jitter I reported previously.  I have not
> figured out which variable controls this period.