pretty much like the BlackBox: OpenBuilds BlackBox 4X Documentation except refer to Spark-Concepts/xPro-V4 and use the Spindle PWM terminal (same as BlackBox's Toolhead connector, it has just about the same pins just different order)
I know the XPRO V3 is obsolete so I went to spark concepts web site and installed relay box to the spindle PWM and it turns thew spindle off and on but it does not regulate the the RPM
Correct, but the IOT Relay is just a "relay" - can switch or or switch off... it cannot do speed control. For that you need a SuperPID (and modify your router to remove the onboard speed control - pretty unsafe high voltage work) or a VFD Spindle
