SKR V1.3 with Smoothiefirmware

i am currently converting a K40 to a SKR V1.3 so that I can work with Lightburn. In the meantime, a smoothie firmware is initially running on the board without a machine. I put fire and PWM on outputs with LEDs so that I can watch what happens. During my test I noticed:

  1. If the axes are not moving then fire and PWM are off
  2. When I move by hand, fire is off but PWM is on
  3. When a contour is followed, fire is always on and PWM is switched off on the empty paths.
    Is that normal?
    I had actually thought that PWM is always on and fire only comes on when an element is cut.



Moving axes by hand turns your steppers into generators and pushes uncontrolled voltage back into your board.

An unwise practice.

Cohesion3D has full configuration, wiring, etc. for smoothieware - they also have the firmware to enable the high-speed cluster mode compatible with Lightburn.

Your board is essentially the same construction, even if it has different labels on the pins.

This is a possibility, but does not apply in this case because the output is also switched if no motors are connected at all.

Of course, I wouldn’t twist the motors by hand!
I’ll let the engines go through Lightburn!

This effect also occurs when I remove the 2208! So definitely get off the board!

Did you ever get the SKR 1.3 working with Smoothieware? I am thinking about going that route if it can be made to work.



Yes it works!
I connected it like this:

  1. The ribbon cable from the K40 to a middleman board and from there 4 cables from the X axis to the SKR stepper. In addition, GND, 5V and the two limit switches in the SKR.
  2. 24V and GND from the laser power supply to the SKR
  3. L from the laser power supply to HE1 (-) from the SKR
  4. IN from the laser power supply to the servo from the SKR
    Then the firmware from Cohesion3D + changed config.txt


Thank you for the info. If you don’t mind I have a couple of questions, but I understand if you have time. What exactly does the middleman board do? Is it just the endstops that it converts? Also would you mind if you have time I would like to see your configuration file and any information you think would be helpful? Don’t go out of your way though. I am suprised just how little information there is information this. I have a 3d printer and there is so much info, documentation, how to guides, etc. I am planning on making a how to guide and it would be nice to see your settings also.



I know the problem with so little information! I also spent many hours looking for useful help on the Internet and only ever found part of the answers.
The Middelman board can be used to convert the K40 laser to another controller. The K40 has a ribbon cable to connect a stepper motor and the two limit switches to the board. If you build your own laser then you don’t need Middelman. You could also replace the ribbon cable with cables, but I wanted to be able to easily rebuild it. Now I’ve solved it in such a way that only a few plugs have to be plugged in and the old one, or a completely different one, is installed. As I see there are several control options for the K40 or any other laser:

  1. The original board of the K40. The disadvantage is that the performance cannot be changed and that the performance cannot be dynamically adjusted to the speed!
  2. Boards like the Ruida. They can do everything, but are far too expensive for me
  3. Low cost boards like the SKR V1.3 that I bought for 30 euros. The advantage is a lot of computing power, both marlin and smoothie are possible, displays can be easily connected. The disadvantage is that you can actually give yourself a display with the laser because the firmware would have to be adapted to display all possible options. The variables can be adjusted directly via the Litghtburn console.
  4. A board that is GRBL compatible such as an Arduino Uno.
    The current firmware 1.1 can also dynamically adjust the laser power and runs with Lightburn. There is also a lot of freeware such as LaserGRBL and the installation of the firmware is just as easy as that for Smoothie. The GRBL variables can also be adjusted directly from the software.
    Now that the thing with the SKR is running, I will next test the solution with the GRBL board.

looking for best way to upgrade controller on a new K40. The specs on the BBT skr v1.3 look good. If i needed to replace the controller on our 3d printer, this board looks perfect.
My question:
What are the problems to overcome in using the SKR v1.3 in a K40 laser.?


dick d

should have asked this in the previous.

would the Almencla Smoothieboard (5X) v1.1 be a better choice than the BBT skr v1.3?

also thanks


It has ethernet, the 120MHz processor, and 5 axes.

It’s a direct copy of the Smoothieboard 5X. I have a bunch of them.

They don’t say which driver they’re using, but I can’t see them copying everything exactly and then not using A5984’s

If it’s built correctly, that’s a great board. The downside is that you need a 5V supply or a 5V transformer from your core stepper voltage on the board. I have a bunch of suitable units on hand, so it was never a problem, but if you don’t have 5V to feed it as well as 24-36V, it’s a pita until you work out why :slight_smile:

Hello Wolfgang,
I have the same setup as you and I am trying to figure out some things. I’ve read your post here and also your other post here (I’ve re-read that whole thread at least 10 times as all the info there was very confusing and sometimes conflicting with each other and I am still not fully sure I understood everything :grinning:). Anyway, I see hat you have connected your SKR 1.3 differently than others have suggested. You use the PSU IN pin to control the power instead of PWM’ing the L pin.Which makes sense to me, but still unsure of some things.
So I have a few questions, if you don’t mind.

  • If you have PSU L connected to HE1- (pin 2.4), I assume in config you have that assigned to switch.laserfire.output_pin, correct? Is it as “2.4!^” ? And any reason you are using (-) pin 2.4 instead of 2.3?
  • you have PSU IN connected to servo pin 2.0, correct? And in config it’s assigned to laser_module_pin?
  • how do you use the config-get and config-set to edit the config file? You mentioned it but I can’t find any more information.

Do you still have your original digital panel with added manual potentiometer connected to the SKR board (to lower the power manually if needed)? Or do you control power exclusively with the Smoothieware config? With your setup, I am really not sure how could I connect that panel, because originally the output of the panel goes the PSU IN, but now the servo pin goes there. Unless I am missing something.

And do you think you could share your config file with me? It would make things much clearer to me, I am sure.


here is the config file.
I can no longer say why I used 2.4 and not 2.3.
To read out parameters you enter “config-get acceleration”
and if you want to set a parameter “config-set sd acceleration 2500”
But I have noticed that sometimes the parameters are not adopted.
The potentiometer is completely disconnected and is no longer needed because I do everything with the SKR!
Everything is really easy now. Yesterday I installed an electric table that is moved via the Z-axis, it works too!

config.txt (23.7 KB)

Thank you for the config, Wolfgang!
I was finally able to make my laser work as it should. PWM to IN, Fire to L, GND to GND.
I had the same issue like you with using only the L to PWM control the laser. The engraving didn’t work properly. Now works looks great!
I only miss the Fire test button on the digital panel. Will have to figure out a way to add a separate fire button. Or does your Test Fire button on the digital panel work? If yes, how do you have the wires connected?
(I assume you have used pin 2.4 because it has a screw terminal and pin 2.3 needs a special connector. But functionality seems to be the same. I use pin 2.3 because I already made a connector and it works as it should.)

I plan to add the Z-axis table as well. Would you mind sharing what table have you built? Something from Thingiverse or your own design?

I noticed that I basically don’t need a test fire and if it is needed very rarely, I do it via the software.
As a table, I have my own design. I designed it in such a way that I mill a lower plate and an upper plate with my CNC milling machine and then only need a few 3D printed parts. If you also have the option to mill plywood or HPL then I could send you the files, otherwise there are many constructions that are assembled from profiles.

That make sense…using the fire button from within the software.
I might be able to use CNC machine at work and I do have a 3D printer. If you don’t mind sharing your design it would be great.

You can find the files for my table in the file.
Tell me if anything is unclear.
Bauanleitung Tisch eigen.txt (979.1 KB)
You have to replace the ending txt with zip!

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