Is it possible to run GRBL with H-Bridges?

YES

I'm happy to announce that the effort made by @rakshithbk [GitHub - rakshithbk/GRBL-H-Bridge: A simple arduino CNC plotter which uses GRLB with H-bridge for driving Stepper motors. Uses DC motor for pen control mechanism.] to port GRBL onto H-bridge devices is remade by me ^^.

Some explanations and instructions I've uploaded here.

The goal was to build a complete system that emulates real machines out of CD-ROMs and possibly cheapest parts. I will not try to explain how to build it here since many howtos can be found on the internet.
Parts I used: two h-bridges (despite high voltage drop - only ~3V out of 5 goes to steppers), cheap USB charger, two steppers from CD/DVD-ROM, laser.

How to modify further versions is explained on my page, so go there and read if You want. There are also modified files ready-to-upload.

What was sacrificed:

  • there is no longer Z-axis. I believe it MIGHT be possible sacrificing other pins eg. spindle direction or analog.
  • no Z-limit. Also, it might be worth trying to back it up when Z-axis, but not in this project.
  • motor enabled. Stepper drives need to be turned on always.

All the rest of functionality should be intact, but even limits weren't tested yet.

What can be done:

  • I'm going to implement my (not published yet) microstepper library for H-Bridges. Yes, it is possible and I made enough tests to say "it works!". So maybe in version 1.1 ;). It uses PWM so it may or may not work with GRBL (but I believe it will).
  • restore motors enable/disable and Z-probe functionality by sacrificing analog pins.
  • sacrifice more analog pins to restore Z-axis. Microstepping for three steppers is impossible, so only full steps are an option.

I would be very happy if You can test this modification and comment on what do you like about it :wink:

Go and test it, by downloading from here!

Best Regards!