Hi,

Where can I find the electric scheme to control the stepper motor of the extruder with the Motherboard ( v1.2) and a Stepper Motor Driver (v2.3)? I'm using in my Mendel (Gen3) the h-bridges of the Extruder Controller for this, so isn't it necessary to modify the firmware to use a external driver?

here is a good starting place

[reprap.org]

Ok, thanks. It's very simple, like this scheme [www.flickr.com]. But I'm using the enable pin connected to ground, and the step and direction pins are connected with the motherboard with the SDA and SCL pins. It's working with the same firmware.