UM controller: USB port x disabled by hub (EMI?) problem

[ummaxx13 0]

Hello,

I have a 3d-printer that uses UM controller as electronics (board revision should be be a v1.5.3), and I have a problem connecting to it from my Linux computer,

If I connect to the printer with e.g. Pronterface or Cura while I'm hooked via USB but with power supply off, I can get an answer from the Arduino Mega inside (and the Linux connection goes via /dev/ttyACM0), but when I flip the power switch on, the connection is dropped.

In Linux syslog I get a "USB port x disabled by hub (EMI?), re-enabling" error and then the available terminal becomes /dev/ttyACM1. If I try to reconnect to the printer with power on, it fails.

The only way to get the machine to print is to use an old laptop with WinXP... perhaps it is less sensible to electrical noise?

What should I do to troubleshoot and fix the issue? Add some kind of filtering on the power supply block and/or a 'soft-start' circuit? The PSU provides 19V so it's inside the recommended range for UM controller.

BTW: I'm building my own Ultipanel with sd-card support, etc. so I can avoid entirely the issue of connecting a computer to start a print :-P

Thanks