I was using MACH3 to a PC printer port but that computer died and I’ve had to settle on a solution using a USB connection. EstlCAM seems to translate my Gcodes to accurate cutting (GRBL might have done as well) but I’ve settled on ESTLCAM for now. The problem was adapting the USB signals to my breakout board which expects to plug into a PC printer port. There are many designs of breakout board available at very low prices which also expect a PC printer input and they all seem to use different pin sets for their signals. I have designed and built a small Circuit board which, using Prototype connector leads (available on Aliexpress, 40 or more for $3 or less) connects an Arduino Nano to a 25-pin D-connector in an entirely configurable way. A 26-pin header connection for a ribbon cable is also provided for signals which the breakout board does not handle. I’ve attached a .ZIP file here which contains Eagle design files, GCode milling files and photos to aid in reproducing the board.

I hope other DIY builders find this useful.
Peter.