Thanks for the hint. I will try to set stepspace at a higher value.
And i know about the newer Drivers. I already use DRV8825 for a new
project and it is far superior to the old L297/L298 combo.
At the moment i just want to get the old hardware running and i already
have planed to replace the old driver with a new one somewhere in the
future. But as long as it works for my intention it is ok. :)
Ciao,
Rainer
Am 02.06.21 um 18:31 schrieb Chris Albertson:
That 0.5 uS spec is for the minimum time the clock needs to be low.
STEPLEN is the time to remain high. You have STEPSPACE=0 which means the
low time is to be "0 nanoseconds". I'd make STEPSPACE much larger.
BTW, that L297 is primitive at best. You'd be amazed at how much better
the new stepper drivers are and the price has come down. You get much
better performance (more speed and torque) and no high-pitched noise.
Something like one of these on each axis would be a great upgrade. Buy a
24V or 35V power supply to go with it.
.omc-stepperonline.com/digital-stepper-driver/digital-stepper-driver-18~56a-20-50vdc-for-nema-23-24-34-stepper-motor-dm556t.html
<https://www.omc-stepperonline.com/digital-stepper-driver/digital-stepper-driver-18~56a-20-50vdc-for-nema-23-24-34-stepper-motor-dm556t.html>
On Wed, Jun 2, 2021 at 5:48 AM Fox Mulder <[email protected]> wrote:
Hi,
i try to reactivate my old self-build cnc mill with stepper motors and
come to a little problem. My 15 year old electronics seems all still to
work. It uses L297/L298 stepper drivers driven by the parallel port from
my old pc which is quite outdated but this doesn't matter at the moment.
I reinstalled Debian with LinuxCNC v2.8.1 and at first start it updated
my old config files. But then when i try to jog one of my axes it
doesn't work. I only get some jitter from the motors but no movement.
After some investigation i found out that the width of the step pulses
is too small. At the moment they are ~2,3µs which should be valid
because the datasheet of the L297 says a minimum of 0,5µs is ok. But
when i try the step generation with a simple python script which has a
wider step pulse the motors move how they should. So i think i can get
it to work again with a wider pulse.
Now to my question, how to make the pulse width for the step signal
wider. I read in the stepgen module about the steplen parameter but it
seems i'm not setting it correct.
In my old hal file the configuration for the stepgen module looks like
this:
loadrt stepgen step_type=0,0,0
addf stepgen.make-pulses base-thread
addf stepgen.capture-position servo-thread
addf stepgen.update-freq servo-thread
setp stepgen.0.position-scale [JOINT_0]SCALE
setp stepgen.0.steplen 1
setp stepgen.0.stepspace 0
setp stepgen.0.dirhold 51056
setp stepgen.0.dirsetup 21056
setp stepgen.0.maxaccel [JOINT_0]STEPGEN_MAXACCEL
Now i tried to increase steplen to something like 10000 and expected a
step pulse width of ~10µs but nothing changes. The pulse width is still
~2,3µs.
Is there something i'm missing or what is the best way to change the
pulse width of the generated step signal?
Ciao,
Rainer
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