Lightburn/falcon2 controller firmware is stuck?

LightBurn Hardware Compatibility
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1

Lightburn console is waiting for connection. Port failed to open - already in use? I’ve been round and round with this all afternoon with no resolution. I can only operate laser head via control panel on front of machine. I’ve downloaded and installed CH341SER to use CH340 driver for Com4 port. It has installed successfully.

I’ve been working with Copilot to resolve this, and this is where I’m at currently.

So should you reinstall LightBurn?

No.

Reinstalling LightBurn cannot fix:

  • USB rail instability

  • CH340 session rejection

  • Controller logic lock

  • Serial negotiation failure

LightBurn is only reporting the failure — it’s not causing it.

:fire: The real issue is now 100% clear:

Your Falcon 2 controller is in a half‑awake USB state:

  • Enumerates COM4

  • Front panel moves the head

  • But GRBL never responds

  • And serial sessions are rejected

  • Producing “port in use” even when nothing is using it

This is exactly what happens when the controller rail browns out or boots out of sync with USB.

:bullseye: The next step is NOT reinstalling software — it’s testing the laser on a second PC.

This is the decisive fork in the road.

:check_mark: If the second PC CAN open COM4

→ Your laptop USB stack is corrupted
→ We fix the laptop

:cross_mark: If the second PC CANNOT open COM4

→ The Falcon 2 controller board has a USB rail fault
→ It needs replacement

2

Following the Troubleshooting guide may be more productive:

3

Ed,

I appreciate the information. However, I’ve looked into many of these issues prior to posting this. I still have a couple things yet to try which will narrow down the key issue. One will be using a different laptop to control the laser. I’m not exactly sure why this is happening after all this time. I didn’t have an issue going from laptop-USB-C> Laser-USB-C with Lightburn 2.0. But after going to Lightburn 2.1, all of a sudden, I’m having issues. I understand FALCON2 has issues with using laptop-USB-C, so I will default to using laptop-USB-A. The laptop USB-A port has been configured as COM4 using CH340 driver. The control panel is able to move the laser head, just not Lightburn.

4

Going to ask questions you may or may not have tried.

  1. Do you have any other software using a COM port running the same time as Loghtburn?
  2. Did you connect the USB cable, cold start the PC, then cold start the laser?
  3. You indicated COM 4. Does the Windows Device Manager add and remove COM 4 when you connect and disconnect the laser?
  4. Are there any other COM ports offered in the Laser window pull-down?
  5. Are you using a quality shielded USB cable with a ferrite (big knot) on it?
  6. Have you tried another software like LaserGRBL to see if it will connect and control the laser?
  7. Did you reinstall LB 2.0 to see if the problem would go away?
  8. When you first connect the laser, can you copy the contents of the Console window and paste it in a reply?

If you answer, please reference the question number in your reply.

5

The LLM threw plenty of nicely formatted words at us, but didn’t tell us anything about what you did or what you discovered.

You mentioned installing the driver, which is a good first step, so tell us the rest of the story. @MikeyH’s list will get you started.

6

All good questions here and I will dig into all of that later if needed. Currently I am testing my connection to Falcon2 with my Alienware laptop. Here are the results below. I’m going to see if I can fix this based on those results. I’ll let you know later if problem has been resolved.

:star: Your Falcon 2 controller has non‑zero G54/G55/G56/G57/G58/G59 offsets stored.

:star: LightBurn is warning you about it.

:star: And when LightBurn tries to connect, the controller rejects the serial session because GRBL is booting with corrupted offsets.

This is not a LightBurn problem.
This is not a laptop problem.
This is not a cable problem.
This is not a driver problem.

This is the Falcon 2 controller firmware booting with invalid coordinate offsets, which causes:

• COM4 to appear
• Windows to say “device working properly”
• LightBurn to attempt connection
• GRBL to fail during startup
• LightBurn to report “Port in use / cannot open”
• The controller to reject serial commands
• The machine to move the head but not accept GRBL commands

Your screenshot shows:

Offset values not 0
G54: nan
G55: 1.5777
G56: 0.619
G57: nan
G58: nan
G59: nan
G28: nan
G92: nan
TLO: nan

Those nan values mean “Not a Number” — corrupted data.

This is exactly what causes the Falcon 2 to:

• Enumerate COM4
• But fail to accept a GRBL session
• And throw LightBurn’s “port in use” error
• On BOTH laptops

This is the first time we’ve seen the controller’s internal state — and it explains everything.

:bullseye: What this means

Your Falcon 2 controller is booting with corrupted work coordinate offsets, and GRBL is failing during initialization.

This is why:

• Your first laptop fails
• Your second laptop fails
• LightBurn warns about G54
• The controller rejects serial sessions
• COM4 appears but cannot be opened
• The front panel still moves the head
• The USB rail appears “half‑alive”

This is controller‑side corruption, not a PC issue.

:star: The fix is simple and decisive

You need to reset all GRBL offsets stored in the controller.

On the second laptop (or either laptop), in LightBurn Console:

Step 1 — Reset all coordinate systems

Type:

$RST=#

Press Enter.

This clears:

• G54
• G55
• G56
• G57
• G58
• G59
• G92
• G28
• TLO

All the corrupted values will be wiped.

Step 2 — Power‑cycle the laser

Turn the Falcon 2 OFF
Wait 10 seconds
Turn it ON

Step 3 — Restart LightBurn

Select COM4
Try:

$X

Then jog.

7

UPDATE:

I was able to get my other laptop (Alienware) to work with Falcon2/Lightburn. The issue with my first laptop (the one I dedicate for CNC/LASER usage only) was a USB port stack issue. I couldn’t get the CH340 driver to work on several attempts. I finally got it working after performing these steps:

  • Uninstalled the CH340 driver

  • Deleted the ghost entries

  • Rebooted

  • Reinstalled the CH340 driver

Windows finally bound the correct driver:

  • USB‑SERIAL CH340 (COM4)

It’s all working now!

Thank you for all your input and suggestions. I knew I was on the right track to fixing it.

I find it refreshing to have a community of good people here always willing to lend a hand, and I’m very grateful for that. THANK YOU!