Angular axis only reaches half of maximum speed

Hi All. Yesterday, I experienced with strange behavior of chinese DM542 stepper driver. This driver I have recently bought so do not know exactly how should it work.

The issue: Motor connected to the driver increases its speed up to approximately half of my maximum pulse rate then it proportionally decelerates to almost full stop at maximum pulse rate then when the joint decelerates behavior exactly the same but reversed. LinuxCNC shows speed as it should be.

My setup: LinuxCNC Maximum pulse rate 27.2kHz, Driver steps per revolution 1600, Driver voltage 24V, Driver current ~3.3A, Motor coil inductance 2.5mH

I tried to swap this driver with one from another axis (also chinese but different noname brand) and it works as expected, I also tried to swap parport pins to be sure there is no issue in joints configs and it does not help.

Anyone experienced such issue? I suspect that driver is "a sick driver"

Seams like you did miss the stepgen acceleration
Doubel the latency
############
Why did you use so mutch Multiplication
You shoudt try to get it down to 400 by Hardware
or not more then 800

Calculation
at BallbearingSpindle is 200Steps Motor Half stepping 400steps /revelution Will lead to a 1,25 gear Meaning timingbelt 20Z/25Z gives you accuraccy of 0,01mm per step lots of Force and Best speed

adding Multiplicator 4 so 200*4 = 800steps /rev will give you a direct drive
But Not a good acceleration as the Force will kill your speed

Not sure about acceleration. I increased it but that did not help. I recorded video for better understanding of the issue. On video I start rapid move at 61Kdegre/min. Then was reducing speed down to 31Kdegree/min where motor rotation is stable. It really looks like the driver "eats" steps.

P.S. 1/8 was my preferred settings where I do not see resonance on linear axis, now, I just try to figure out where is the problem. The driver must work up to 25600Kpulse per minute

P.S.P.S. Right now I am connecting the driver to one of linear axis, will see how it goes

Okay, after connecting the driver to X linear axis everything works as expected. So, driver is OK. It is configuration issue. I will investigate my HAL .

Thanks for reply

It sounds/looks like your exceeding your driver's maximum step rate, then it starts to only see half of the steps sent to it.

(double check your drive's minimum step spacing in it's documentation, and set it as such plus some safety margin.)

No, no ... I configured all my joints XYYZA to have exactly the same maximum pulse rate 27200Hz in my case. All joints have exactly the same timings in hal. Looks like ANGULAR axis does not want to move at that rate. If I rewire A axis' driver to X axis or remap pins in HAL and jog that linear axis then motor on A axis turns properly but if I try to jog angular axis it only reaches half of that speed then decelerates.

It looks like there is signed overflow in LinuxCNC code

Looks like I have found culprit, need some time to check that out an then I will reply

Solved, by reading manual!!!

Namely this

1.6. Using DoubleStep

I have added reset string after write addf parport.1.reset base-thread and A axis, connected to my second parport (thatI did not tell you at the begging) works as expected.

Thanks to all

Good to hear you found the problem.