Laser power MIN / MAX for other controller like the LPC1768

The min / max power function also for other processors like the LPC1768 (SKR V1.xx) and not only for DSP boards!

Is that a feature request?
If the controller won’t support it, it can’t ‘magically’ work in lightburn. But i’ll leave it to the experts to give you a definitive response…

Yes, this is a feature request.
The processor just works from the commands that it receives from Lightburn. When engraving, it is also done in such a way that each time the laser power changes, a different S value is also transferred. If you cut a rectangle and approach a corner, the speed is reduced. What speaks against it at the end of the corner to transfer smaller line pieces with different laser power? This would make this function possible with any processor that can engrave!

GCode controllers don’t have any way to send this option. A GCode controller manages its own acceleration and movement speed, and when it slows for corners, it manages the power ramping itself. GRBL LPC has a firmware setting for the minimum PWM output value, but that can’t be changed while streaming a job.

I understand that but if I output a grid line as part of an image, then it is possible to transmit different speeds and laser powers for partial paths of different lengths, right?

That would require LightBurn to completely take over the motion / acceleration planning for the controller, or at least understand where the controller was going to slow down, and break the lines up, and emit different power output settings for each segment, and they would need to be constant power in order to work.

That would still fail in many cases - For example, if you were burning an image, and the controller was unable to keep up with the rate of the GCode being sent, it would slow down by itself, and I have no control over that, so the image burn would be very inconsistent.

Ok i can understand that!
The following consideration: The acceleration is known! With this, Lightburn can predict how the speed will change and would only have to reduce the laser power at the end of a line, right?

In theory, yes. However, as I said there are quite a few reasons why this would cause other issues, so it’s not likely something we’d do, especially since GRBL-LPC already supports this setting in the firmware itself. If you’re trying to prevent the laser from cutting out at the corners, increase the minimum PWM output setting until it’s just below the firing threshold of the laser.

We have a change coming that will allow you to choose constant power or variable power mode per layer, which will make cutting with a CO2 laser using GRBL much easier, and will still behave properly for things like vector marking.

Could it be that GRBL 1.1 already supports this?

Not that I have seen. That would be a question for the GRBL developers.

At GRBL there is now a mode that does just that. For this the parameter $ 32 = 1 must be set and at the beginning of the job there must be M4 and not M3!
Can you change or set that in Lightburn?
Doku GRBL 1.1

If using the “GRBL” device in LightBurn, you’re already using the M4 mode. You have to use the “GRBL-M3” device in LightBurn for it to use the M3 mode.

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