> On 5 Apr 2018, at 09:50, Rick Mann <rm...@latencyzero.com> wrote:
> 
> After help from Bas (thank you), I got MachineKit working on a Beaglebone 
> Black and driving a ClearPath stepper. Here's a video:
> 
>    https://www.youtube.com/watch?v=f3kdqH8Miyg
> 

That's a hefty stepper.

> I notice on the oscilloscope (but not visible in the video above) that the 
> step direction output changes when I stop jogging and the servo slows down 
> from the jog speed it was going at.
> 
> Can anyone tell me why it does this? Is it in an effort to "apply the brakes" 
> to the moving stepper? This is not necessary with the ClearPath servo, which 
> will faithfully the number of steps commanded at the commanded speed (within 
> limits, of course).

This looks like "hunting" from the Pru stepgen. A solution for this is to drive 
the stepgen in velocity mode, and add a PID loop. Have a search thru the google 
group posts about this phenomenon.

This configuration can be an example on how to do this.
https://github.com/machinekit/machinekit/blob/master/configs/ARM/BeagleBone/Xylotex/Xylotex.hal


One thing to check are the specs of your driver regarding the timing of the 
step and direction signals.

dirsetup dirhold steplen and stepspace.

These should be at least (but longer would be preferable) as long as the specs 
from your driver.

> For reference, the HAL file <https://pastebin.com/cMTUiW7u>, and the .ini 
> file <https://pastebin.com/eBLxpUh4>. Note I've only adjusted the pin 
> addresses for axis 0 in the HAL, and the path to the PRU binary in the .ini. 
> It's the same as the pru-stepper otherwise.
> 
> Thanks!
> 
> -- 
> Rick
> 
> -- 
> website: http://www.machinekit.io blog: http://blog.machinekit.io github: 
> https://github.com/machinekit
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