G-code compatiblity with H-bridge L293d (Bipolar Stepper Motor Driver )

I'm trying to make a 3 axis bipolar stepper driver and I think using L293Ds and Arduino is the best cheapest option. I have seen people using grbl to run their steppers easily but with grbl they have used expensive Easy drivers or Adafruit motor shield. I can't use them and I want my motors to run from H-bridges only. What can I do to make grbl compatible with H-bridges or is there any other software ? I have googled a lot and seems to me it is the most common issue people face since grbl doesn't officially support H-bridges.

What sort of stepping motors? I assume they are bi-phase.
This tells you what patterns they need.
All you have to do is two write a very small function that will output the next step in the sequence given a direction. Just graft that into the place where the code steps the motor.