I'm testing a stepper motor using the Allegro A4979 stepper motor controller
When I powered the devkit from +5 and disconnected the USB cable, I couldn't get the FAULT LED to go away,
I tried powering the USB interface from +5 also, but that didn't work either.
I started checking logic levels with a volt meter, and found out that RESET* was always low even when I switches the DIP switch that's supposed to control it.
RESET* and ENABLE are transistor-or'd together so that either the USB chip or the DIP switch can control them.
Probing around told me that the transistor was not letting go of RESET* even when the USB interface was powered down.
So we cut the part out and now I can run the board just with STEP and DIRECTION inputs.
Unboxing shows a PCB and a CDROM.
Plug in the CDROM and I get a "READMEFIRST.TXT" file that says:
1) Click on Setup...
2) Then plug in the USB cable.
USB CABLE???? For a stepper motor driver?
Well, they have some really poor GUI for click-n-test that has NO documentation, will connect to ANY attached FTDI USB interface (Such as the FTDI cable I have running my arduino) and makes a general mess on things.
After a half-day, I got the darn thing stepping from the Arduino, but I'll have to figure out how to get it running without starting up the GUI and clicking boxes pretty soon.