On 1/14/2014 12:21 PM, Bas de Bruijn wrote: > Yes, the BeagleBone Black, > the PRU is hat 10us step length and 1us step time. > The servo task period, in nano sec is 1000000. > When i run a latency test i get a jitter of approximately 56000 to 60000 ns > max Jitter > > I’ll disable the screensaver to check.
The latency you report is typical for the BeagleBone. The "unexpected realtime delay" is something I see occasionally on my systems. I haven't fully dug into the cause, but it seems like something in LinuxCNC has hard-coded jitter numbers and doesn't like the BeagleBone (which has higher IRQ jitter than a typical x86 system). I've never had it cause issues, however, and it is not correlated with a spike in latency as measured by either the LinuxCNC latency-test or the xenomai latency utility. I also run with the screen saver and display power management enabled on my BeagleBone and have not had any issues with "missed steps". I suggest you review the current setting on your stepper drivers, cooling on the stepper drivers, the mechanical system (make sure everything moves freely and can't bind), and review your machine setup. I did have to dial my acceleration down to around 2400 mm/s/s to avoid missing steps with some Slic3r generated infill gcode, but that had nothing to do with the BeagleBone, my steppers and drivers just weren't up to the task when running off 12V. -- Charles Steinkuehler char...@steinkuehler.net
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