Mach3 with Hitachi VFD using Modbus

Has anyone setup Mach3 to control a Hitachi SJ series VFD using modbus?

It looks like it should be possible, the basic setup using autopolling is covered in the wiki. I can pretty much understand mapping the Run, FW/REV functions to virtual pins in Mach.

What I don't understand is how to map the spindle speed. The VFD has a holding register that sets the drive frequency with an input value of 0-4000. Can this be used to set the drive speed? How would it work?

ALso, there is another holding register that displays the output current that the drive is delivering. Is it possible to display this value on the Mach3 screen, and/or scale it before it gets displayed? This would allow me to have have a spindle 'load meter' showing the electrical current being pulled by the motor.

Swinn

Did you firgure this out/get an answer??
It sounds like I have the same setup and would like to pick your brain about how to get the most out of the setup.

No, I never did figure these issues out. I got the basic modbus commands working for start/stop. The speed and output displays I never did get working, or the variable speed. It has been quite a while since I worked on it, but I remember that i had to use an RS-232 to RS485 converter and then I had to connect a resistor in parallel with each end of the 485 wires in order to get the signal to go through.