Robin2:
How many amps can your power supply provide? Measuring the current going to the DRV8825 is not meaningful. Do you have the 100µF capacitor across the power supply?
Thanks for the reply Robin:
Yes, 100uf 63v capacitor just as in the modified diagram shown above.
PSU is a 10v 600mA wall wart, but the DRV8825 only seems to draw 160mA.
As I mentioned, even if I load the standard BLink program, and no PINS are connected to the DRV8825, the humming/grinding/stuttering noise exists.
I don't think the driver is dead, I have only measured voltage at the pin leads while powered on (never disconnected accidentally). To test regardless, I used a new DRV8825 and after VRef adjustment to 0.68V, I came to the same results.
I am thinking do I need to upgrade my PSU to a higher amperage? Regardless of what VRef is outputting? Some how 160mA draw at VMot is not making sense....