My read (moderate, not deep dive) of the info on the Amazon listing finds no mention of a PWM compatible input.
From comments made by reviewers, it is hard to determine what documentation you get with the unit. That said, some of the reviewers seem to have figured it out and are please with the results.
tinyG has three spindle control outputs, On/Off, CW/CCW and SpinPWM, a variable duty cycle pulse train that varies the torque generated by the spindle and therefore its RPM.
The typical(default) VFD controller interface is an analog voltage in the range of 0-10V, I believe.
It is my understanding that Machx interfaces provided an output for VFD control, so I am confused by the comment that MACH3 is not compatible with this unit.
It is possible to convert the tinyG SpinPWM signal to an analog voltage using an external filter circuit and perhaps an amplifier. The tinyG output is 3volt logic.
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