new build with Mesa 7i76ED and old Dell

Hi All,

I decided to replace my direct parallel port stepper system with a Mesa board. I've got it all put together but it only works some of the time. When I launch linuxCNC, I see the 4 green LEDs on the Mesa light up. If I turn off the power to the Mesa and launch linuxCNC I do get an error so I'm reasonably sure they are talking when powered normally. Once linuxCNC is up, I press F1 and then F2 and try to jog one of the axis. If it works, they all work. If it doesn't they all don't. I've never see it come back to life once it's in this state. Restarting linuxCNC will bring it back to life maybe 1 time out of 5. The other odd thing is that if I'm in the working state and I take linuxCNC to full screen, I've lost the steppers. I've had this happen twice. In the running state I've also seen moving the jog slider kills the steppers. In all cases the screen continues to update.

Any thoughts where I should look?
thanks,
Steve

Can you post your hal and ini files here?

If you can continue to jog when the drives are not working, and you have no error messages (and a standard hal file setup),
this means that communications are working properly with the 7I76E

Is it possible you have a wiring error with the drives or possibly marginal timing?
(double the step time to see if that makes a difference)

Edit:
Having graphic operations cause functional problems at the hal/hardware level sounds suspiciously like latency issues
Did you run a latency test on the system?

Hi Peter,

Thanks for the reply. The motors and drivers are Compumotor Series M. They should be able to take 500ns step pulses according to the manual but I did try and set them to 1us and it didn't change the reliability. Each axis has a separate driver so I would have had to make the (an) error 3 times. It does work some time. It's acting like there's a setting that allows linuxCNC to run without moving the motors. I'm not aware of any such setting.

I did run the latency test but I was under the impression that going to an external step generator made the system less susceptible to latency issues. This seem more like a binary thing. It's with working or it's not. Just for giggles, I did try and disable sound and the floppy drive in the BIOS. No difference.

Thanks,
Steve

The only thing I can think of that would disable all steppers is a watchdog bite
You might try setting the watchdog timeout longer (its currently 5 ms)

Bingo! I set it to 50ms and I get success 5 out of 5 launches. What's a good value to use? I thought 5ms was the default in PNCconf.

thanks,
Steve

I think it is the default but its probably too short for some slower machines

Also a watchdog bite should pop-up a error warning but there are some versions of LinuxCNC that don't do this. I know this is fixed in 2.8 not sure about 2.7