So I was reading the 3d printer guide again today and got to the external stepper section and it donned on me that I could add another stepper If I understand this correctly. What I have on my Z axis is two 0.9 deg stepper motors that need 1.68A each, more than the 2A that one driver can handle so I have the other one slaved on the one that could be used for a second extruder. So, my question is can I add an external driver to the EN3 breakouts and still use the on board driver also. So each stepper would have its own driver set to 1.68, freeing up EN5 to use as the second extruder?
I had my printer setup the same way, until I added a second extruder. My experience was that if you use an external driver that uses 3.5 volt input it might work. My driver was a 5 volt and when I changed the pins to ground so I could use the 5 volt driver, then only that driver worked and the internal one did not. So what I did was to buy an external driver rated a 4 amps, hooked it to the pins for the z driver and ran both motors off of the same driver as it had more than enough amperage to do so. I think the driver was about $20. It works quite well and now I have my second extruder working.