PWM on 7i76

Hi all, I am trying to control the speed of a brushed DC motor with drive that accepts PWM input. The drive is VNH5019 from Pololu: www.pololu.com/product/1451

I would like to setup the 7i76 with PWM output on the open step/dir pins since the motor drive accepts up to 5V, and I am currently running the Field I/O at 12V on the 7i76. Is this something that can be done with the appropriate hal settings or do I need a new bitfile for the 7i76?

Alternatively, would it be easier to just use the GPIO? I've read the resolution is lower doing it this way, but I don't think that will be a problem. I will then need change the Field I/O to 5V, and move the 12V to VIN on the 7i76, correct?

freeby.mesanet.com/5i25_7i76x2_1P.bit
should be about right (stepgen 04 replaced with PWMGen)

Another option if you did not want to lose a stepgen on the 7I76
would be to add a pwmgen on the second 5I25 connector only
and wire to it direct or through a cheap parallel port breakout

Thanks, for now I can lose the last stepgen, but I will keep that in mind for future machines.

Is it possible to have the DIR+ pin on the 7i76 default to 0V like the DIR- pin? The motor drive I am using has two inputs for direction and uses the truth table below to determine direction.

High | High | Brake
High | Low | CW
Low | High | CCW
Low | Low | Brake

The current setup for the direction pins works when LinuxCNC is running, but if I turn off the program my motor will just run continuously since there is always 5V on the DIR+ pin.

No this is not possible since the DIR- and DIR+ pins are complements
Can you chose the PWM polarity so PWM is off when LinuxCNC is not running?