The maximum step frequency depends on your PRU task loop time, which depends on how many tasks you're actually running. By default, the PRU task loop is 10 uS, which means step pulses can be generated every 20 uS (one period high, one period low) minimum, which gives a 50 KHz maximum step frequency. You can dial the PRU task period down if you need higher frequencies and are not running lots of tasks. IIRC the default setup I was using for my 3D printer took about 1.5 uS to run the code (4 stepgens and 3 PWMs), so there's a lot of safety margin.
On 2/26/2014 11:38 AM, Mark Tucker wrote: > I eventually managed to merge a few hal files and ini files to Change > the stepgens etc to work in velocity mode. > I have just connected up to the machine,and initial testing is excellent. > Strange thing though ,i have not entered any deadband figures yet but > the crackling seems to have gone. > I will let you know how more in depth testing works out, but for now all > is good. > Can anyone tell me what the maximum figure is that i can set in the > beaglebone for stepgen max velocity? > At the moment my stepgen max velocity is 42 > And the Max velocity is 35 > At 1000 steps per mm > I seem to remember it max's out at 45khz? > > On 24/02/14 17:22, Jeff wrote: >> Hi, >> >> I'm *guessing* that they are the older Geckos (non digital). The older >> drives had to have the DIR line stable for quite a time after the STEP >> pulse. I believe this was to manage the resonance compensation circuit. >> This makes me think the DIR line was not actually latched at the time of the >> STEP pulse. If this is the case, the external DIR line would play an active >> role in the direction the current is going to be going in the motor >> windings. Thus, at the start of each PWM cycle (about 20KHz) the DIR line >> would determine which direction the current should go (even in a stationary >> motor). As the DIR line changes, the standby current in the motor will be >> reversed. The rate of DIR reversal coupled with the 20KHz ends up giving a >> beat frequency in the audible range. Another guess would be that the actual >> noise "signature" would be where the drive stopped within the 10 microstep >> range. You could end up having 10 different crackling noise characteristics >> depending on which m icrostep you stopped at. >> >> While the noise might be annoying, I don't think (another guess) it would >> cause a problem for the drive as long as the correct DIR polarity is stable >> before the next STEP pulse comes in. >> >> Jeff >> >> ---------------------------------------- >>> Date: Sat, 22 Feb 2014 11:30:59 -0800 >>> From: [email protected] >>> To: [email protected] >>> Subject: Re: [Emc-users] Crackling motors using Beaglebone >>> >>> On Sat, 22 Feb 2014, Mark Tucker wrote: >>> >>>> Date: Sat, 22 Feb 2014 19:20:57 +0000 >>>> From: Mark Tucker <[email protected]> >>>> Reply-To: "Enhanced Machine Controller (EMC)" >>>> <[email protected]> >>>> To: "Enhanced Machine Controller (EMC)" <[email protected]> >>>> Subject: Re: [Emc-users] Crackling motors using Beaglebone >>>> >>>> John >>>> >>>> Thank you so much for the insight of how that work and it explains a lot. >>>> But as you stated it would be hunting back and forth.Which i assume it >>>> would have to pulse the step line? >>>> And a number of people have scoped the outputs and only found the Dir >>>> line hunting back and forth,i wonder why it is not detected on the step >>>> line.? >>>> And if it is only the dir line,why would the motors make a noise at all? >>> >>> The internal stepgen position has a resolution of a small fraction of a step >>> (1/10000 of a step in Johns example) so it can hunt back and forth without >>> emitting a step. >>> >>> As to why a step drive pays any attention to the dir signal without a step >>> pulse I do not know, seems like a mistake to me. >>> >>> >>> Peter Wallace >>> Mesa Electronics >>> >>> ------------------------------------------------------------------------------ >>> Managing the Performance of Cloud-Based Applications >>> Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. >>> Read the Whitepaper. >>> http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk >>> _______________________________________________ >>> Emc-users mailing list >>> [email protected] >>> https://lists.sourceforge.net/lists/listinfo/emc-users >>> >> ------------------------------------------------------------------------------ >> Flow-based real-time traffic analytics software. Cisco certified tool. >> Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer >> Customize your own dashboards, set traffic alerts and generate reports. >> Network behavioral analysis & security monitoring. All-in-one tool. >> http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users >> >> > > > > ------------------------------------------------------------------------------ > Flow-based real-time traffic analytics software. Cisco certified tool. > Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer > Customize your own dashboards, set traffic alerts and generate reports. > Network behavioral analysis & security monitoring. All-in-one tool. > http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Charles Steinkuehler [email protected]
signature.asc
Description: OpenPGP digital signature
------------------------------------------------------------------------------ Flow-based real-time traffic analytics software. Cisco certified tool. Monitor traffic, SLAs, QoS, Medianet, WAAS etc. with NetFlow Analyzer Customize your own dashboards, set traffic alerts and generate reports. Network behavioral analysis & security monitoring. All-in-one tool. http://pubads.g.doubleclick.net/gampad/clk?id=126839071&iu=/4140/ostg.clktrk
_______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
