Cheap (<20€) and Easy to build ESTLCam controller based on Arduino Mega
DC-isolation (incl separate ground) between PC/USB and Inputs/Spindle Control → prevents most of the USB problems with inverter spindles.
3 Axis Screw Terminals for Stepper Drivers
Spindle Relais and 0-10V PWM output
3 additional Outputs via Screw Terminals
5 opto-isolated Inputs via Screw Terminals
4 additional Outputs on Header
6 additional Inputs on Header
12 pin header for Pendant / Handwheel