Sanguionolu 1.3a + A4988

If I was wondering, what should I do about the pull up resistors (R2, R3, R4 and R5) on the Sanguinolu 1.3a if I'm using A4988 Stepper drivers (that do not need pull-up resistors)? Do I remove them and leave an open circuit, do I replace them with jumpers or can I just leave them in place without them doing any harm?.

I'm leaning towards replacing them with jumpers, but I'd rather ask someone who knows more than I do before I make any changes.

Or am I totally misunderstanding the purpose of R2-R5? If so I'm curious what they're used for (never done anything more complex than a simple Arduino setup in digital circuitry).

This is the MS1 pull-down resistor. (MS2 and MS3 have internal pull-down)

So R1 is the LED Current limit, while 2-5 are the MS1 Pull-down for the pololu's.

From: [ultimachine.com]

Note: This board is a drop-in replacement for the original Pololu A4983 stepper motor driver carrier. The newer A4988 offers overcurrent protection and has an internal 100k pull-down on the MS1 microstep selection pin, but it is otherwise virtually identical to the A4983.

This is not needed in 1.3A if I'm reading this correctly. Try without a jumper to see if they still have connection, if not throw in a plain wire jumper.

Edited 1 time(s). Last edit at 11/18/2011 09:00AM by marnargulus.

Oh, it's a pull down. In that case shorting the resistor would cause the stepper driver to be stuck in Full step mode thanks to grounding MS1 and by extension 2 and 3. And looking over the schematic again; the right course would be to either sever the trace leading from resistor to MS1 or remove the resistor.

Can you describe your results before and after removing the resistor?

I didn't try put the stepper drivers onto the board before removing them. Now they're moving the steppers as expected.

so if i just got my A4988's and already have my sanguinololu soldered with the resistors will i have a problem?

ok i tried it with the A4988's and the pullups on the board and it works just fine (except for the extruder for some reason)