I bought a HICON mini board. I am configuring the CNC shelf and I want to control the spindle motor with PWM.
However, the manual also does not mention how to configure PWM speed control. There are four output pins, which one is it?

I'm also interested in this (@hicon).  I have programmed an arduino to sample the pulse rate and turn it into PWM, but it is not ideal for a lot of reasons, including needing high frequencey for spindle accuracy and stop detection.  I'm not having problems maybe with the hicon board not being able to put out enough pulses?

HiCON can  only put out pulse/direction or analog or ethercat depending on which model you have bought.  Sorry PWM is not possible.