I've looked around and have been reading lots of posts and haven't come across this subject yet (surprisingly).
I've had a need in the past to be able to utilize the extruder
for an unknown distance. However, continually clicking on the extrude button is slow and becomes annoying and tedious. Using a button until I see filament come out is easier and more efficient. (If you extrude too much and your extrude speed is set too high, this will either cause a jam or the extruder gear cuts a groove into one spot of your filament)
Using Pronterface I can change filament colors halfway through the print, but if I extrude more than I reversed, when I resume the print it reverses again the extra amount I extruded. (let me know if you don't follow that).
That's not my problem. I've worked around, and can prevent that.
What I want to know is, Is it possible to add a button to a couple available pins on the Sanguinololu (or Melzi) to activate the extruder (or any Pololu stepper)
MANUALLY? (During printing or while not printing) I have a microSD card plugged into some pins and I know that you can plug another board into some available pins to upgrade for multi color printing.
Or can I add a button to the Pololu's output directly?
I understand that the firmware will have to be modified for this. Not knowing how to write code myself, it's a lot to learn for such a small goal, but I'm willing to learn if it's possible.
If adding a button IS possible, then my second question would be: Is it possible to add a potentiometer with the button to control extruder speed?
And finally adding a switch or pcb or something to select which Pololu stepper I want? (this part isn't important)
