Lightburn USB/Machine interface poorly coded

had already mentioned it in the other thread about the limit switches on the sculpfun s9 and now tested it again. from time to time the usb connection to the laser breaks down. sometimes plugging/unplugging helps sometimes the laser must be switched off and the program closed.

and - no - it is not the usb-cable or anything else to blame. the same happens under candle or lasergrbl exactly zero.

so dear lightburn team - this needs to be improved. lightburn is really a nice and well made program with a good user interface at a very reasonable price. but the nicest laser program is a bit pointless if it is not connected with the laser.


p.s. and if the interfacing to the machine is improved - how about a milling module that one could buy for about 30$ as an option? would then also bring new sales.

How do you know it is the Lightburn side of the USB interface that has the issue?

Why not Sculpfun’s embedded USB implementation?

Why not your PC drivers?

like i had written: with candle lasergrbl and ugs this doesn’t happen once with the same file->computer->driver->cable->laser. that simple.

Funny, I’ve noticed the same thing. My 3d printer (grbl, usb) and the other machines for pcb using candle.

None have problems hanging onto a usb port.

As you know it’s the same interface, so who’s calling it differently or other parameters … As Tom points out, seems to be how Lightburn manages it, at least from an inference view.

Never needed (that’s ‘have time’) to ‘dive’ into the source… maybe you would… ?


No Diving! But seriously,
Lightburn isn’t open source and the release folder is the product that is available to customers. The source code isn’t even available to a clear majority of the LightBurn team, let alone enthusiasts or customers.

The confusion may be caused by the crackerjack Linux guys managing a library patch for gstreamer to Ubuntu 20.4 and 18.4 by telling the builder to build with one thing (gstreamer) from Ubuntu 16.4. It’s more of a ‘Hey LightBurn, while installing - look here for this book’ than anything else.

I learned a thing or two that day.

I appreciate the clarity here.

I would be interested to know which baud rates are selected in Candle and lasergrbl. Someone posted a while back that they had to hard set the baud rate to 115200 in LightBurn to connect with a particular Sculpfun or Atomstack. This is not shown to be necessary with a vast majority of Sculpfun devices. General USB noise and line length are considerably more common - You’ve clearly dispelled this. There is also a switch in LightBurn (in Device settings) to Enable DTR signal. I would also like to know if Candle and lasergrbl use DTR as part of their communication process.

115200 - confirmed here:


I saw the entry on github… surprised but never dove into it.

This seems more likely as the root issue…

This has always eluded me… I started communication protocols when I starting in the industry in the 70’s and the DTR (Data Terminal Ready) signal is on an rs-232 communication line…

I know usb is a differentiated single line protocol… How is DTR implemented in this protocol with no actual communication control signal lines? Is this something the ch340 driver emulates?

If you don’t know, I understand… I’ve always wondered and you brought it up :face_with_spiral_eyes:

I’m going to push down the baud rate and then enable dtr… My usb is running at 115200b. Doubt I’ll notice much of a difference… even the slowest is probably much faster than what it’s plugged into… :crazy_face:


and i appreciate your software. and especially your nowadays more and more rare fair licensing system that doesn’t want to force an outrageous subscription model like adobe & co on the customers. the way you do it is the best compromise of the advantages of opensource and professional software!

all programs (incl. lightburn) are set to 115200 by default. lasergrbl uses the default usb-serial setting. i don’t know which usb-dialect the other two programs use.

in any case i’ll try your tip with the setting ‘dtr’ under the machine settings. all in all i think you shouldn’t break it down too much to manufacturer/machine type because that only complicates things unnecessarily. the fact is that the other programs seem to react much more resilient to possible errors in the usb-communication. here a programmer who is specialized in this interface should really take a closer look at the issue in lightburn.

if and how far the setting ‘dtr’ brings something i will post here in a few days when it has been proven in use.


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