I would really appreciate a little poke in the right direction on this.
The problem I am having is that I can not for the life of me figure out how to get Mach 4 to display my spindle rpm. I can see that mach is seeing the spindle index pulse on the diagnostics page but I have no idea how to get this information displayed on the 'current spindle rpm' dro. I'm sure its something really simple but I have no idea what I'm missing.
The setup I'm using is a pokeys 57cnc and I'm feeding a digital pulse to it from an arduino (this is a simple test setup so that I can see that mach is seeing the index pulse).
many thanks for looking and any advice you may have.

I am pretty sure (but not positive) that this is a plug-in issue.  As far as I know the Mach4 core doesn't do anything with the index signal except record whether the index is high or low (1 or 0), and then tell all the plug-ins that the index input has changed state.  The device needs to calculate the actual spindle RPM and tell pass that along to the plug-in which in turn tells Mach4.  At higher RPMs, it becomes impractical if not downright impossible for the device to inform Mach4 of every transition on the index input.

Thanks for the reply, looks like I will have to see if the pokeys thread can help sort this out.
It's becoming a bit frustrating looking at settings in the config that your think should do something but end up doing nothing!

I am using Mach 4 and the SmartBOB-USB.  I see the spindle input toggling in both the Mach 4 diagnostic and the SmartBOB real time port display when I run the spindle but there is no RPM display in Mach.  I suspect I'm missing some set up step.  In Mach 4, I have the index pin configured as an input from SmartBOB.  Thanks for any advice.

Answered here:

http://www.pmdx.com/PMDX-Forums/index.php?topic=196.0

Bob