Is the vfd mapping simply setting minimum rpm and max rpm? Or is this something I need specs from the vfd or spindle?
For these values, you want the min and max RPM for the VFD/Spindle. I don’t know if it the same Vevor VFD you’re using, but in this topic the range for that VFD is 12000-24000 R/min. You could also calculate the range empirically. You could hookup your VFD to PC9, put the VFD in PWM mode, Send M42 g-codes to marlin with S0 and S255, and read the RPMs from the VFD display. Or, maybe it is documented in the manual.
So i was wondering if there is another pwm pin on the skr pro v1.2 that uses 5vdc for pwm
I could not find any reference for what pins support PWM. If you want an educated guess, take a look at the datasheet for the STM32 processor (used in the SKR Pro). The pin definitions start on page 42. PWM requires a timer, so any pin where the definition contains “TIM[something]” is a good candidate for a PWM pin. But, as mentioned in my previous post, I don’t see any reason to seek out a 5V pin. Devices that take PWM signals generally are interested in what percent of each cycle is high vs. low. They don’t care about the voltage as long as the incoming signal has a high voltge above the midpoint of the defined PWM voltage of the device.