Cura 4.13.5 will not connect to Legacy Mini 1.03

I have an older mini (1.03 “gladiola”, I think) with an Aerostruder toolhead and firmware 1.1.8.4. I was using another slicer (not Cura) and Octoprint to drive it. I am giving away this printer, so wanted to get it working directly with Cura over USB, to simplify things for the recipient.

I installed Cura 4.13.5 on a Windows11 laptop and connected the Mini via USB. Cura had trouble connecting to the printer. It would rarely connect (perhaps 1 out of 10 tries), usually failing with some kind of “printer does not accept commands” and/or a dialog saying “No Response”.

I used Cura 4.13.5 to flash recommended firmware (1.1.9.34). That completed successfully, but Cura still will not connect. Same behavior as described above. Reading messages here, I saw a suggestion to set “Developer Settings, Allow connection to wrong printers”. I tried that, but it did not have any effect – Cura 4.13.5 still won’t connect.

I installed the older Cura 3.6.40 on the same laptop. It connects to the printer just fine, every time. I confirmed the firmware update done by 4.13.5 was successful; a M115 command returns 1.1.9.34. I sliced and printed a rocktopus in PETG. No problems with Cura 3.6.40 controlling the Mini over USB. Likewise, I installed Simplify3d and it had no trouble connecting and controlling the Mini over USB.

Same laptop, same cable, same drivers, same firmware… Cura 3.6.40 and Simplify3d connect just fine, but Cura 4.13.5 will not connect.

The problem with Cura 4.13.5 seems like a baud rate issue. Both Cura 3.6.40 and Simplify3d have the baud rate set at 250000. But Cura 4.13.5 seems to have REMOVED the ability to manually specify the baud rate. (I also tried the “experimental” Cura 4.13.6 – will not connect, same as 4.13.5.)

Is there ANY WAY to manually force the baud rate in Cura 4.13.5? Any other suggestions?

Oh, and… I installed Ultimaker Cura 5.6.0 as well (same laptop, same cable). It connects and controls the Mini correctly – no problems connecting.

So, I only have the connectivity problem with Cura LE 4.13.5. All the other software (Cura LE 3.6.40, Simplify3d, Ultimaker Cura 5.6.0, Octoprint) can connect and control the Mini just fine.

I would like to manually set Cura LE 4.13.5 to use 250000 baud instead of it’s “automatic” detection, as it sure looks like that is the problem. Failing that, I guess I’m stuck with Cura 3.6.40 because I want the Lulzbot profiles and additional material attributes Aleph/Fargo added to LE, which don’t exist in the Ultimaker releases.

Created an issue on Gitlab for investigation.
Cura LE 4 fails to connect over USB with Lulzbot Mini 1.03 Gladiola (#243) · Issues · LulzBot 3D / Cura LE / Cura LE · GitLab

We have seen some issues with Windows 11.
You will need to look into your USB power settings and ensure that the USB port power is always on as Windows 11 does suspend USB power settings for whatever reason.
This can cause the computer to not see the printer and now allow a connection.

No, this is not a Windows 11 or USB power problem.

I replicated the same behavior on a Windows10 desktop machine, which has all sleep/suspend disabled. Read the issue on Gitlab for more info. The set of tests I posted yesterday were done on a Windows10 desktop.

In addition, the problem is with initial connection, not losing connection during a long print (as can happen with suspend settings). Once a good connection is established (which can take 20+ attempts), I can run an hours-long print without issue on either machine.

So it looks like our software team is looking into this a bit more and hopefully find something helpful.

I have ran a few tests in house on our legacy printers (Taz 5 and older Mini 1s) and personally have not found issues with connection through Windows 10 and 11, so it may not be as cut and dry of a problem that some users may be experiencing.

I would definitely follow through GitLab for any updates.

I have a similar problem, which has not been resolved:

@Dave - Sounds like that could be the same issue. Good news – it appears the cause has been found and a probable fix will be in the next “experimental” build. Details are on the Gitlab issue linked in earlier post. Fantastic and quick response from the developer! When the next build is available, I’ll test and follow-up here.

Great news, thanks. I am glad you got involved, I have been waiting quite some time. Dave

Version 4.13.7-EXPv1 was released. The potential fix mentioned earlier was included, but unfortunately did not resolve the issue.

Since then, more testing and investigation has pinpointed the root cause and a simple fix. I would expect that fix to be included in the next experimental release. (I manually made the change on my installation, and now have 100% successful connections to the Mini!)

I will follow-up here when I see the fix in a released version.

Again, many thanks for your diligence. Please post when a fix it out.
Thanks again

The released version of 4.13.7 is now available at LulzBot | Cura LE Windows and has fully resolved this issue for me. With version 4.13.7, I now have 100% success connecting to the Mini1.

Many thanks to Spencer F. at Lulzbot for the quick response and comprehensive code fixes!