LinuxCNC-RIO - RealtimeIO for LinuxCNC based on FPGA (ICE40 / ECP5)

It's not that the motors stall during acceleration. The run for like 50mm normal. I try to make a video. And the weird thing is, it works with the parallel port. I can switch back and forth between the Tang and the parallel port.

Tonight I focused on getting my handwheel working. RIO is just a fantastic software!

I was also able to get a video of the problem of my Y axis.

I noticed a few things: The units in the display of LinuxCNC are sometimes jumping around a little bit. I think that was discussed somewhere earlier her. Will dig that out. Maybe that's the reason why I measured Step pulses and the motors shake even when I did not move an axis.

A few words to my machine. X and Z are are Nema 23 Motors (23HS30-2804S) with www.omc-stepperonline.com/digital-steppe...stepper-motor-dm332t DM332T driver. Z Axis has the highest resolution 5mm pitch ball screw and 3200 microsteps/round. Brings it to a scale in LinuxCNC of 800. As shown in the video I have no issues going up to 3600mm/min.

The Y Axis have 2x  www.microkinetics.com/index.php?page=stepper_motors/34m450 34M450 Microkinetics Motors with www.microkinetics.com/pdfmanuals/DM8010.pdf DM8010 Driver.5mm pitch ball screw and 2000 microsteps/round. Scale 640 in Linuxcnc. I limited the axis to 1950mm/min, but it's still stalling.

All axis are connected over the same Breakout board with no level shifter.

I doubt that the problem has something to do with RIO, but I am not sure. Still a myth what the problem is.

Well, first of all sorry. I tried to edit the last message on my phone and it screwed up and made 1/2 of the message to a link.

Anyway. I made some progress. I was curios why the Y axis motors making this weird sound when they are not moving and shaking a bit. I connected the oscilloscope to the Tang and depending on when I the movement I get the following signals on step and dir. The signals can look different which makes the motors sound different and sometimes i even stop at a point where no signal is produced. It feels like the tang is doing some sort of position holding or so.

Again, this is when the axis are not in a commanded move. It happens on X,Y,Y,and Z. X and Z just have different motors and I can't hear or feel it.

What could cause that?

DIR
 
Step
 

.....
Thinking about it more with your comment, I think maybe the machine is moving the correct amount, but the position reported back to LinuxCNC isn't correct or isn't stable, for some reason. How can I look into this further? If it were just floating point rounding error, once the iceshield had arrived at the correct position, shouldn't the reported position then be stable at the rounded value, instead of flicker? My X axis is very coarse, so I am comfortable with it not having high precision, but the flickering reported value (shown in the DRO) is very odd given that it's a stepper.

Do I need to re-flash with each change of scale, or is modifying it in the .ini sufficient?

For reference, 
config:  github.com/digiexchris/6x11-sg-grinder-l...reconfig/config.json
generated ini:  github.com/digiexchris/6x11-sg-grinder-l...eld/LinuxCNC/rio.ini

but I have changed the scale to 11.64 (yes, very coarse) for the X axis but that's what was required to get 10mm of movement from G1 X10 with a surface grinder table driven off of the normal handwheel (it's quite a large movement per handwheel turn)


I think I'll change the microstepping up to 32k so I can get the scale number higher and see what effect that has on the stability of the reported position.

if i set the deadband to :
DEADBAND           = 0.0001

my DRO shows the exact position like 10.000 or 0.000
 
 

Have you tried to set in the LinuxCNC Display section?

you can try setting the DEADBAND a little higher again to see if the trembling goes away.

It is at least due to the PID controller, but unfortunately I don't have a good solution at the moment

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and please forgive me, I'm not a professional either and don't have an answer to every problem

Hey, no problem! I appreciate the hard work you do for this project!!

I increased the deadband to 0.01 and switched the position back to Actual. The jumping of the numbers stopped and the motors don't make that weird noise anymore. I will test it with the oscilloscope, but I am sure that brought me one step more where I want to be. I wanna say that the motors are not stalling as early anymore.

I played around with the PID settings and thought this would help with the problem, but no change so far.