grbl is stepper motor controller firmware for three-axis cnc machines, intended to run on Arduinos with a motor driver add-on board. Engineer in Wonderland cnc-related blogs are indexed here It is the ...

Universal (ish) Arduino grbl opto-coupler interface also works with logic-level pwm In adding an alternative cutter drive motor (‘spindle’) to an existing cnc machine, an electrically isolated pwm to ...

There’s extensive documentation, GRBL settings, and more pictures in their GitHub repo, too – in case you have a similar CNC and would like to learn about upgrading its controller board!

A cheap off-the-shelf USB to DB25 adapter may look like a good idea at first glance but they won’t work for a CNC application. [Bray’s] adapter is Arduino-based and runs GRBL.