Connect Siggen to Stepgen?

I am working at tuning some older digital (step/dir command) servos, that don't have any auto tuning capabilities.  In order to avoid needing to use an  oscillo scope I would like to be able to connect a square wave siggen signal to the velocity command input of an unused stepgen on a 7i76eu (I also have a 5i85 for encoder feedback.)  I loaded the siggen, and made the hal connections, set all the parameters and enabled everything from halshow.  I can see the input for the stepgen's velocity-cmd changing, but I don't think any steps are being generated (no changes of any of the stepgen's count or feedback pins.  

Where am I going wrong?  Is this another situation where changes to parameter pins are only effective in a hal file at startup?

I was hoping to just create a little hal file that I can load manually after Linuxcnc was running to set tuning parameters then plug one of the drives step/dir plugs into the testing plug to run the tuning (moving them back to their regular position when running.)

Did you set the stepgen to control mode 1?  (velocity mode)

I use stepgens all the time for encoder and frequency counter testing
so this will work.

Sserial parameters can only be set in the hal file, this is not true of general
hostmot2 parameters.

Also of you want a step frequency change, you will have so set the stepgen acceleration
to a large number