DRV 8825 EVM USB Opcode for DIR

I wish to control the EVM board on a Linux system.

First, is there any example code to control the board over Linux?

If not, AppDeff.h in the firmware gives the opcodes, which I believe I send to the USB port. What is the boards port?  Or is it assigned at runtime? I can see START_STEPPER, STOP_STEPPER< STEPPER_SPEED, and MOVE_STEPS. I do not see DIR.  Do I set that using the GPIO? 

The DRV8825 is fed through P4.4/TB4. Do I sues TBCCTL4 as a GPIO?

Thanks

Ralph