Having bought the DC-Motor Plug from Jeelabs.org with the intention of using it with a stepper, i finally made it and got the code running for driving a small stepper motor.
I’ve used the dcmotor_demo as base for heading off the other direction.
As you can see, it is relatively easy to use. Most of the „bitbanging“ is happening within the functions for fullsteps (fstep_cw and fstep_ccw) and halfsteps (hstep_cw and hstep_ccw).
You can get the source to work with from github: