This is an old revision of the document!
Cura developer is recommending not to print through USB anymore. This part of function is now working as plugins module.
USB printing not working on Cura 2.3
Original USB Printing plugins will communicate with STH500, which is a firmware update program for AVR. However, this program does not close serial port correctly before plugins started baud rate detection. This problem will cause USB port cannot open and failed detecting USB printer.
Comment out Line 301 will solve. File: C:\Program Files\Cura 2.3\plugins\USBPrinting\USBPrinterOutputDevice.py
Line 300-302: (Before):
programmer = stk500v2.Stk500v2()
Line 300-302: (After):
#programmer = stk500v2.Stk500v2()