Spindle with step/dir stops at 480rpm

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01 May 2024 21:10 #299509 by Murphy_ia
I am running a 600w servo with t3d servo driver, servo is rated at 3000rpm, jogging from the driver it did 3500 with ease. Running it from linuxcnc it stops at 480rpm.
I am using a raspberry pi 5 with a cheap chinese 5axis BOB, got my steppers and limitswitches working as they should, but setting up the servo has me stumped. Servo is set up in velocity mode in hal. For some reason stepgen is limited to 8000steps a second, the servo has 1000 steps pr rotation. Servo does the commanded speed perfect up to 480 but I cant get it to go faster and cant find where the limits on the stepgen is. I have tried to change steplen, stepspace, dirhold, dirsetup velocity and scale, scale affects the motor speed up to 480 but there it stops, I cant see any difference in the other settings.
If I enable maxvel in hal i get an error message saying stepgen is limited to 8000steps pr second. Is there any way I can change this?

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File Name: Murph.hal
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File Name: Murph.ini
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01 May 2024 22:55 #299516 by tommylight
If possible, you will have to set the spindle to 100-150 steps per rotation, otherwise you will need to spring for a Mesa board.
The number of steps RPI can generate is very limited, while Mesa can do several MHz per second.

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02 May 2024 00:21 #299519 by PCW
You have a 16 KHz base thread, this limits you to a 8 KHz step rate
unless you use reset mode. If the GPIO driver supports this (reset mode) 
this should double your possible step rate to the base thread rate.

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