Tuning Geeetech DRV8825 drivers

I recently got five Geeetech-branded DRV8825 drivers. They are rated high enough to burn out my steppers, so I need to adjust them
The Geeetech wiki says what sense resistors they have, and it says to measure the voltage between vref and ground, but as far as I can tell, the Vref contact is just wired to the input voltage.

Also, there seems to be no voltage across the tuning pot, like it's not being used.

I don't have an Arduino hooked to the RAMPS, would that make a difference?

Anyone know how to tune these?

Did you ever find out how to tune your Geeetech DRV8825's?
I've got a set I'm dying to try out, but I can't figure out how to tune them.
Should they be connected to the steppers?
Should the Ramps be connected to 12v or instead should the Arduino only be powered by USB?

I've tried leaving the steppers disconnected and measuring VREF with 12v connected to the Ramps, in which case I measured 12v!
I've also tried using just USB power, in which case I measured 0v.

I am about to set up my 8825's as well. I will probably use a clamp meter to measure the current going to each stepper coil once they are powered up. Maybe the input current will do it too. On my CNC foam cutter motor temperature is a pretty good indicator as well, warm to the touch after they have been on for a while is good.