This is a mod of ljyiang stepper controller (http://www.thingiverse.com/thing:4966). This is a drop-in replacement for GEN3 RepRap stepper controller. The PCB is single-sided and easy to produce.This stepper controller can replace standard Reprap GEN3 controllers. The connectors are exactly at the same location than the original, so the upgrade is really straightforward. You can use a Pololu driver or an equivalent, and benefit from micro-stepping.You must build at least 2 of these boards ( for X and Y axes ). You can keep your original board on Z axis if you want.After installation, a few steps are required :see : http://www.diygallery.com/en/2012/07/interface-moteur-pas-a-pas-pour-reprap-gen3/En français / in french : http://www.diygallery.com/2012/07/interface-moteur-pas-a-pas-pour-reprap-gen3/