Originally Posted by
Hermitude
For anyone in a similar situation, I have a LY Group 1.5kW CNC kit that came fully assembled and it is set up the same way. I've probed the spindle output of the BL-USBMach board with a scope, and no alteration of the settings will result in a PWM signal emitted from the board. The board has a 4-pin spindle connection, of which only one signal pin and one ground pin are connected. The other two unwired pins probe to noisy versions of the signal pin or ground.
The signal pin is 1V when the spindle is ON, and GND when the spindle is OFF. Interestingly, when the board starts up and before the BL-USBMach driver has been loaded, the signal pin is +10V.
The potentiometer is fed straight to the VFD board and since this VFD is not a standard terminal block wiring like a HuanYang unit or any other common VFD, I am not going to mess with it. I also don't have a manual for it. I don't know how they've wired the potentiometer signal into the VFD, and don't have any reasonable indication that the BL-USBMach would be able to give it a proper signal anyway.
So, looks like these are manual control only.