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- kb0thn
10 Mar 2026 11:31
Replied by kb0thn on topic Laser power scaling based on speed and direction
Much thanks to iforce2d for this implementation and write-up. I just deployed a slightly tweaked version of it to my 4x10' router that has a 40 watt laser as second spindle.
I had to modify the component to force zero power output when there was no motion. It looks like the original first line of code can result in a NaN and then my machine was ending up with a 50% PWM output in that state. So I force NaN to zero. That worked okay in my testing at a fixed z height. But when running an actual program I retract Z between parts and I was finding that Z only motion was leaving the laser stuck on. So now I also force zero power output when X and Y motion are essentially zero.
I use a bunch of MESA cards including a 7I77 and a 7I76. And then some additional IO boards linked via serial. I never figured out how to get a hardware PWM output. So I am using software PWM for driving the laser. Here are the relevant sections of my custom.hal file showing how it all goes together:
I had to modify the component to force zero power output when there was no motion. It looks like the original first line of code can result in a NaN and then my machine was ending up with a 50% PWM output in that state. So I force NaN to zero. That worked okay in my testing at a fixed z height. But when running an actual program I retract Z between parts and I was finding that Z only motion was leaving the laser stuck on. So now I also force zero power output when X and Y motion are essentially zero.
Code:
component aprs_laserreg "";
pin in float inpower "Desired laser power at constant speed";
pin in float reqspd "Requested speed, connect to motion.requested-vel";
pin in float curspd "Current speed, connect to motion.current-vel";
pin in float velx "Current speed x component, connect to joint.0.vel-cmd";
pin in float vely "Current speed y component, connect to joint.1.vel-cmd";
pin in float velz "Current speed y component, connect to joint.1.vel-cmd";
pin in float share "Fraction of power given to pure Y movement, eg. 0.6";
pin out float outpower "Scaled output laser power";
function _ fp "Update the laser power";
license "GPL";
;;
#include <math.h>
FUNCTION(_) {
outpower = inpower * (curspd / reqspd);
float angle = atan2(fabs(velx), fabs(vely)); // angle away from y in radians
float horz = angle / (0.5*M_PI); // 1 when moving perfectly along x axis
outpower *= share + (1-share) * horz;
if ( outpower > inpower )
outpower = inpower;
if ( outpower > 100 )
outpower = 100;
if ( ( fabs(velx)<1e-6 && fabs(vely)<1e-6 ) || isnan(outpower) || outpower < 0 )
outpower = 0;
}
I use a bunch of MESA cards including a 7I77 and a 7I76. And then some additional IO boards linked via serial. I never figured out how to get a hardware PWM output. So I am using software PWM for driving the laser. Here are the relevant sections of my custom.hal file showing how it all goes together:
Code:
# laser engraver
# software PWM
loadrt pwmgen output_type=0
addf pwmgen.update servo-thread
addf pwmgen.make-pulses servo-thread # should be base-thread
setp pwmgen.0.enable TRUE
setp pwmgen.0.scale 65535
# based on https://forum.linuxcnc.org/47-hal-examples/54073-laser-power-scaling-based-on-speed-and-direction
loadrt lincurve personality=2
loadrt aprs_laserreg # for some reason the component gets renamed to aprs-laserreg (ie changes _ to -)
addf lincurve.0 servo-thread
addf aprs-laserreg.0 servo-thread # I don't seem to have a base-thread. I think because it is MESA
# Laser power mapping (0-100 -> 0-65535)
setp lincurve.0.x-val-00 0
setp lincurve.0.y-val-00 0
setp lincurve.0.x-val-01 100
setp lincurve.0.y-val-01 65535
net laser-requested-speed motion.requested-vel => aprs-laserreg.0.reqspd
net laser-current-speed motion.current-vel => aprs-laserreg.0.curspd
net laser-velx joint.0.vel-cmd => aprs-laserreg.0.velx
net laser-vely joint.1.vel-cmd => aprs-laserreg.0.vely
net laser-velz joint.2.vel-cmd => aprs-laserreg.0.velz
setp aprs-laserreg.0.share 1.0
net laser-percent spindle.1.speed-out => aprs-laserreg.0.inpower
net laser-regulated-percent aprs-laserreg.0.outpower => lincurve.0.in
net laser-65535 lincurve.0.out => pwmgen.0.value
net laser-pwm pwmgen.0.pwm => optimat_o_laser_engraver_pwm
# second spindle we will always consider to be at speed
net laser-at-speed => spindle.1.at-speed
sets laser-at-speed true
- Hakan
10 Mar 2026 10:59
Replied by Hakan on topic CiA 402 Folder Missing
It is encoder pulses per mm, maybe your value isn't far off then.
It is suspicious if it start moving very fast. Use halshow to look at the
variables between cia402 and lcec and see if they look ok in size,
moves when they should etc.
It is suspicious if it start moving very fast. Use halshow to look at the
variables between cia402 and lcec and see if they look ok in size,
moves when they should etc.
- Finngineering
10 Mar 2026 09:45
Replied by Finngineering on topic Strange preview for circular arc (G2/G3)
Thank you Hannes. I made a bug report as you suggested:
github.com/LinuxCNC/linuxcnc/issues/3855
This was a real use case and a toolpath I intended to use immediately. I was trying for an hour or so, wondering how I can mess up or misunderstand such a simple command. I then gave up and made this thread some time later. I would think I had the command right from the start, just that incorrect preview threw me off. And I did have a fair bit of confidence in the preview, because I had previously used several somewhat complicated CAM generated programs, and the preview always looked fine. Well, at least I know the reason now.
github.com/LinuxCNC/linuxcnc/issues/3855
This was a real use case and a toolpath I intended to use immediately. I was trying for an hour or so, wondering how I can mess up or misunderstand such a simple command. I then gave up and made this thread some time later. I would think I had the command right from the start, just that incorrect preview threw me off. And I did have a fair bit of confidence in the preview, because I had previously used several somewhat complicated CAM generated programs, and the preview always looked fine. Well, at least I know the reason now.
- Konstantin
10 Mar 2026 07:57
Replied by Konstantin on topic CiA 402 Folder Missing
About the cia402.0.pos-scale, I wrote 100 000 to just start with some value. My encoders are 23bit, therefore 8 388 608 pulses per motor revolution. On my current plasma machine I have a 1:10 planetary gearbox that I plan to use when I upgrade the machine motors to servo motors and LinuxCNC. The rack gear pitch diameter is 50 mm, therefore the circumference is 157.07963267949 mm. This the linear distance that the axis will travel for 1 revolution of the rack gear or 10 revolutions of the motor.
Therefore the cia402.0.pos-scale = ((encoder res * gear ratio)/distance per rev). I am not sure what value I should use for distance per rev - is it the linear distance per the rack gear revolution or the linear distance per motor revolution(that is linear distance per rack gear revolution / gear ratio)?
Therefore the cia402.0.pos-scale = ((encoder res * gear ratio)/distance per rev). I am not sure what value I should use for distance per rev - is it the linear distance per the rack gear revolution or the linear distance per motor revolution(that is linear distance per rack gear revolution / gear ratio)?
- grandixximo
-
10 Mar 2026 06:52 - 11 Mar 2026 07:44
After reviewing on real hardware today, I found my original PR works better than what Sascha Ittner did in his repo, I reverted back to the original state before I started reviewing Sasha's work.
If anyone wants to help me test, I'd love feedback on the code in my repo, because for me this is what works.
github.com/grandixximo/linuxcnc-ethercat
But I need more data from other testers.
To prove the system works, you should get grinding noise, if you set sync0shift of your drive to be half your max servo latency, open halscope and scope your servo-thread and open a couple of glxgears to induce latency in the servo thread, this should induce the grinding noise, and the noise will not be anywhere else.
Replied by grandixximo on topic Ethercat random jitter fix
It sounds like you get gravel in the servo motors from time to time.
Or you get click sounds from the motors. It repeats itself with a few or many minutes apart.
The first thing to do is to enable syncToRefClock and enable DC mode for the servos,
this will keep the servo loop in sync with the DC.
What grandixximo is doing here is fixing an effect that despite DC and servo loop are synchronized,
the two loops have been started with an undetermined/unfortunate phase between them.
The gravel sound is there all the time and it doesn't go away until linuxcnc is restarted.
Surprisingly, yesterday Sasha Ittner popped up in the PR log and mentioned he had been working
on a complete redesign of the DC system, eliminating all these problems (don't know details)
grandixximo seems to have reviewed that work and decided to adopt Sasha's work.
grandixximo will have to say himself. And if you don't know, Sasha Ittner is the author of linuxcnc-ethercat
from many (>10) years ago.
After reviewing on real hardware today, I found my original PR works better than what Sascha Ittner did in his repo, I reverted back to the original state before I started reviewing Sasha's work.
If anyone wants to help me test, I'd love feedback on the code in my repo, because for me this is what works.
github.com/grandixximo/linuxcnc-ethercat
But I need more data from other testers.
To prove the system works, you should get grinding noise, if you set sync0shift of your drive to be half your max servo latency, open halscope and scope your servo-thread and open a couple of glxgears to induce latency in the servo thread, this should induce the grinding noise, and the noise will not be anywhere else.
- Hakan
10 Mar 2026 06:22
Replied by Hakan on topic CiA 402 Folder Missing
Initcmds can be used to set a configuration at startup
github.com/linuxcnc-ethercat/linuxcnc-et...er/examples/initcmds
your cia402.0.pos-scale is very large. Double-check that one.
Set a negative value for refClockSyncCycles="–1", that switches on the PLL to synchronize
servo loop with DC clock. You also have "did not sync in 5000 cycles" in dmesg. I have no
good way of fixing that, eventually the drives will sync their time though.
your cia402.0.pos-scale is very large. Double-check that one.
Set a negative value for refClockSyncCycles="–1", that switches on the PLL to synchronize
servo loop with DC clock. You also have "did not sync in 5000 cycles" in dmesg. I have no
good way of fixing that, eventually the drives will sync their time though.
- rodw
-
10 Mar 2026 05:46
Replied by rodw on topic current latest download of LinuxCNC V2.9.8 will not install GRUB on several PC's
that looks like its looking on the cd/DVD. If this is not on installation, edit your sources file to remove the CD/DVD settings
- Konstantin
10 Mar 2026 05:23
Replied by Konstantin on topic CiA 402 Folder Missing
I talked to the manufacturer of the drives and they told me that the PDO mapping should be set in the control device on each start of the machine.
With the above mentioned configuration I tested the homing and it seems the motor find the index pulse but then it starts rotating very fast and following error is reported.
But the synchronization error is still present.
With the above mentioned configuration I tested the homing and it seems the motor find the index pulse but then it starts rotating very fast and following error is reported.
But the synchronization error is still present.
- Marcos DC
10 Mar 2026 04:30
Replied by Marcos DC on topic Separating CiA402 Logic from EtherCAT (lcec): Modular Adapter + Drive Stub Valid
Hi @NWE,
No worries — things have been a bit busy on my side too
Over the last days I focused on validating the CiA402 logic layer in simulation using a HAL drive stub. The main pieces are behaving as expected now (PDS state machine, controlword composition, homing supervision, etc.).
I also added a small gantry supervisor component on top of the CiA402 layer to experiment with safe decouple/recouple behaviour when drives perform internal motion like CiA402 homing.
At the moment everything is running inside HAL with two simulated drives.
Next step is reconnecting this to the EtherCAT side through an adapter layer.
I'm also planning to write a small Python CLI diagnostic tool to read the HAL signals and print a quick snapshot of the CiA402 state to help with testing.
Your Lichuan drive with 4 axes in one unit is quite interesting — that could be a very good test case once the EtherCAT adapter is wired.
I might also open a separate thread later describing the small framework this is turning into and include your two drives as example adapters.
No rush at all
No worries — things have been a bit busy on my side too
Over the last days I focused on validating the CiA402 logic layer in simulation using a HAL drive stub. The main pieces are behaving as expected now (PDS state machine, controlword composition, homing supervision, etc.).
I also added a small gantry supervisor component on top of the CiA402 layer to experiment with safe decouple/recouple behaviour when drives perform internal motion like CiA402 homing.
At the moment everything is running inside HAL with two simulated drives.
Next step is reconnecting this to the EtherCAT side through an adapter layer.
I'm also planning to write a small Python CLI diagnostic tool to read the HAL signals and print a quick snapshot of the CiA402 state to help with testing.
Your Lichuan drive with 4 axes in one unit is quite interesting — that could be a very good test case once the EtherCAT adapter is wired.
I might also open a separate thread later describing the small framework this is turning into and include your two drives as example adapters.
No rush at all
- hmnijp
10 Mar 2026 04:23 - 10 Mar 2026 04:42
Replied by hmnijp on topic motion channels for robotic atc library
I saw this in a recent PR sent by Sascha Ittner:
github.com/sittner/linuxcnc/pull/70
github.com/LinuxCNC/linuxcnc/pull/3845/c...7ac47d8c5d436a843202
Description: joint_ctrl_main.c
* Standalone HAL realtime component for single-joint control.
*
* Provides: homing, keyboard jogging, jogwheel jogging, trapezoidal
* trajectory planning, following-error monitoring, limit-switch
* handling, and backlash compensation — all as a self-contained
* HAL component independent of the full LinuxCNC motion controller.
github.com/sittner/linuxcnc/pull/70
github.com/LinuxCNC/linuxcnc/pull/3845/c...7ac47d8c5d436a843202
Description: joint_ctrl_main.c
* Standalone HAL realtime component for single-joint control.
*
* Provides: homing, keyboard jogging, jogwheel jogging, trapezoidal
* trajectory planning, following-error monitoring, limit-switch
* handling, and backlash compensation — all as a self-contained
* HAL component independent of the full LinuxCNC motion controller.
- fts
10 Mar 2026 03:09 - 10 Mar 2026 03:16
Replied by fts on topic current latest download of LinuxCNC V2.9.8 will not install GRUB on several PC's
If the installation fails and you want to see what is going on, go back to "Configure the package manager."
Hit Ctrl Alt F4.
You will likely see something like the attached output scrolling down the screen. What is odd in my situation is that even with the network cable plugged in, I am able to ping the host that it claims to be unable to reach.
Hit Ctrl Alt F5, and that will take you back to the GUI where it has gone on to the GRUB installation portion and likely failed at this point.
This is an odd issue to have!
Hit Ctrl Alt F4.
You will likely see something like the attached output scrolling down the screen. What is odd in my situation is that even with the network cable plugged in, I am able to ping the host that it claims to be unable to reach.
Hit Ctrl Alt F5, and that will take you back to the GUI where it has gone on to the GRUB installation portion and likely failed at this point.
This is an odd issue to have!
- rock861261
10 Mar 2026 02:37
Replied by rock861261 on topic El5101 Config
any other suggestions? I can get my enc-index-c-enable to trigger once but I have to turn it on in hal each time. it will also freeze unless i connect the latch. does linuxcnc only care about the Z or does it need a/b as well
- NWE
-
10 Mar 2026 02:16
Replied by NWE on topic Separating CiA402 Logic from EtherCAT (lcec): Modular Adapter + Drive Stub Valid
Same here. It'll be several more days till I get back to this project.image missing /media/kunena/emoticons/smile.pngSorry for the late reply — I was a bit busy the last days.
- rodw
-
09 Mar 2026 23:00
Replied by rodw on topic current latest download of LinuxCNC V2.9.8 will not install GRUB on several PC's
I've recently cloned and built the linuxCNC live builder and created and installed a couple of ISO's without drama. If there are issues with Grub, I suspect I will be due to uefi/secure boot. This is outside of control in our ISO as its pure Debian! But then again Debian 13 has good uefi support.Try and disable it in your BIOS.
The only other issue I had was not finding a couple of obsolete firmware modules sometimes which broke the build process.
firmware-b43-installer
firmware-b43legacy-installer
Apparently, these are a wrapper around a download from flakey servers that have a history of failing. This broke the build process. I just deleted them. There are a number of other very old and probably obsolete Debian non-standard firmware drivers that seem to have been carried over from old builds which I suspect could also be removed.
The only other issue I had was not finding a couple of obsolete firmware modules sometimes which broke the build process.
firmware-b43-installer
firmware-b43legacy-installer
Apparently, these are a wrapper around a download from flakey servers that have a history of failing. This broke the build process. I just deleted them. There are a number of other very old and probably obsolete Debian non-standard firmware drivers that seem to have been carried over from old builds which I suspect could also be removed.
- Hannes
09 Mar 2026 20:56
Replied by Hannes on topic Strange preview for circular arc (G2/G3)
BTW2:
If you want do do helix milling, I created a macro. See It is called like that:
o<boring> call [-10.0] [4.0] [10.0] [1.0] [1000.0] [3000.0]
The center of the helix starts at [0 0 0]. To shift it, I was using a second coordinate system like that:
Probably there are better ways doing this, I'm also just starting writing G-Code. For example you could pass the starting location as a parameter or use variables to create the new coordinate system.
If you want do do helix milling, I created a macro. See It is called like that:
o<boring> call [-10.0] [4.0] [10.0] [1.0] [1000.0] [3000.0]
The center of the helix starts at [0 0 0]. To shift it, I was using a second coordinate system like that:
Code:
G54
G0 X0 Y0 Z0 ;Or what ever the starting position in G54 should be
G10 L20 P2 X10 Y20 Z5 ;Offset of hole relative to actual location ->G55
G55 ;Activate G55
o<boring> call [-10.0] [4.0] [10.0] [1.0] [1000.0] [3000.0]
G54 ;Activate G54 again for future moves
Probably there are better ways doing this, I'm also just starting writing G-Code. For example you could pass the starting location as a parameter or use variables to create the new coordinate system.
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