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.
loop routine of dcmotor_stepper
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).
functions for doing halfsteps clockwise or counter-clockwise
You can get the source to work with from github:
https://github.com/wd77/wd77/tree/master/dcmotor_stepper