"PMDX-SMARTBOB-USB DEVICE ERROR: SYSTEM ERROR (7): Motion Underrun"
I am also getting this error on occasion. It does not seem to occur at the same instance while running my programs. I restart the program and Re-Zero my AXIS since I am afraid that it is loosing its position when this occurs. I have not tried to increase my buffer yet, but will do so.
In addtion to increasing the buffer length, make sure that our plug-in's debug log settings are set to the default. I don't know if you ever actually enabled our debug log during your earlier issues with USB cables (back in Oct). Go to the Mach4 "Configure" menu and select "Plugins...". Then click on the "configure" button for the PMDX SmartBOB. When our configuration dialog displays, click on the "Debug" tab. "Debug Mode" should be "System" and "Debug Device" should be "Windows Debug API".
Let me know if increasing the "GCode buffer len" has any effect.
Bob
Bob