Driver Timing settings for Other in stepconf

Hi. I've posted this at the Probotix Fireball V90 yahoo group and not received any assistance. I am trying to configure linuxcnc to run on a BeagleBone Black using a Xylotex BBB_DB25 to interface with the v90 on a parallel port. The V90 that I have uses their ProboStep VX v1 unipolar microstepping chopper drivers (with a Sanken SLA7078MPR chip). I have successfully installed linuxcnc (2.7.0) from the machinekit image (Debian 7.4) and can run Axis in simulation mode.

I am wondering how to set up the driver characteristics section of the stepper configuration wizard for this system. I've looked at the stepconf screen shots on the Probotix support site and see for this section, the values for Step time, step space are 5000ns and the direction hold and direction setup are 20000ns. However, these screen shots are for an older EMC2 software. In the stepperconf from the linuxcnc that I have installed, I cannot use values greater than 100 ns for step time, step space and Direction hold. Does anyone have a suggestion on how I should set these values up or where I could find them in the datasheet for the chip? Thanks for any help!

What version of linuxcnc are you using?
The timing numbers are found in the INI file and can be edited but its not copied exactly from stepconf entries.

Chris M

Oh I see you are using 2.7 with machinekit - it you can't edit the numbers properly you should file a bug there...
In the mean time I will check linuxcnc's stepconf....

Chris M

Also I hope you realize stepconf will not create a working config for the beaglebone black.
Though you can use it as a starting point and modify it to suit the bbb

Chris M

are you cross posting ? between here and Machinekit
Machinekit is working on the BBB ,
Linuxcnc does not ,
the differences you are seeing are because of differences between a pc & a microcontrolller , these are 2 different beasts .
i think you'll find the differences are in your calculations between ns
it is not required to use exact settings as per datasheets , it's what works for you and the timings your particular board can produce

Thanks Chris. As cncbasher correctly pointed out, I am also posting on the Machinekit GG. A reply there (to a slightly different question) confirmed your recommendation to expect to modify the results of using stepconf. In fact with the Beaglebone black and Xylotex BBB_DB25, I might not even be successful using the "test axis" from within stepconf. Either way, I'll copy the Xylotex conf files and try to modify them directly.
FYI, as I replied to Sarah Armstrong in the Machinekit Google group, the stepconf program hangs when I attempt to "test axis." This is repeatable and hitting cancel after the STEPCONF WARNING check-for-realtime function failed - continuing anyway error appears in the terminal window just brings up a linux unresponsive do you want to kill process window. Even after selecting yes (to kill the process), the activity monitor indicates that the system resources are maxed out and I restart.
Best, N

Guilty as charged cncbasher. I didn't think the Machinekit folks would be interested in the driver timing issues raised here. Both forums have been helpful. Thanks for the comments about PC vs Beaglebone black and the values needed for the driver timing. I'll try to get my issues concerning communication via the Xylotex BBB_DB25 sorted out first (concerns pins 1 and 10 of the parallel port tied together before linuxcnc can control the drive box using configs from Xylotex). Hopefully, the timing values are not that different between the chopper drivers that Probotix uses and those from Xylotex. (I know, wishful thinking ;>)

yes i would expect that as stepconf is looking for the realtime element , which running on a beaglebone won't give the correct results , hence the kill process .

stepconf utilizes the parport and only the parport.
steptiming is on the BBB is done by the stepgen driver on the BBB.
Steptiming on the parport is done in a separate software step driver.
Stepconf is almost useless for creating a config for the BBB

So running a test access in stepconf has stepconf trying to drive a parport.
It shouldn't lockup the terminal - sounds like it needs some help.

If machinekit decides to produce stable releases - I will be more motivated to help these issues.
Trying to maintain a config program on a constantly changing base is frustrating and often broken

Isn't there BBB samples to base your config from?

Chris M

I'd be glad to work with the machinekit folks on helping them solve the issue of stepconf locking up when test axis is chosen (although this is probably such a rare case that I doubt it will rise to the top of their todo).
Per Jeff Pollard's recommendation, I am modifying the Xylotex.ini and setting up a hardware connection on pins 1 and 10. Just getting to the linuxcnc_documentation.pdf to see if I can make the necessary changes to his ini file to work with the Probotix V90. Thanks for your work with linuxcnc. I'm looking forward to finally moving a spindle!

this only happens with using a beaglebone using a pc is fine , which is what stepconf is for .

contact me direct if your still having problems and we can work through and sort them