Pin 2 (D1) on Makerbot G3 motherboard unused?

Hi All

As I am having trouble with my motherboard as detailed here I am wondering if I can remap my SDA output from pin D17 to pin D1 as according to the wiki it seems pin D1 is unused.

Does anyone know otherwise?

Also, in order to convert this pin to seamlessly work as a replacement SDA I would need to attach a 4.7K pullup resistor as per the IC2 headers on the wiki.

Am I on the right track or is this the way to ruin?

Cheers

Edited 1 time(s). Last edit at 11/07/2010 12:54PM by AgeingHippy.

An external pull up resistor is unneeded, the atmel chips have internal pull up resistors that are activated by writing a "1" to that pin.

Pull up resistors are only needed on *inputs* not *outputs* since your using this as an output, it's actively driven high or low, and doesn't need a pull up or pull down resistor.

Likewise on the input side (on the extruder controller) there is an internal pull up resistor that you could activate, but it's not needed as the main controller will be actively pulling it high or low.

Pull up resistors are useful for where you'll be attaching it to ground through a microswitch. The pull up resistor pulls the pin high when it's not connected to ground through the microswitch. That's a common way to do endstops for those who aren't using a optical endstop. Without the pull up resistor the pin can "float" and be at any value, and frequently does change and give more or less random results due to ambient electrical noise.

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I'm building it with Baling Wire

For anyone following... wahoo!!! ><

Redefining the SDA pin to pin 1 as opposed to pin 17 within the firmware (pins.h) seems to have sorted out my problem.

NOTE : It seems that Pin 1 is used on other motherboard definitions. My motherboard is defined as type 2 within the firmware...

Now when I click extrude the motor turns a little, the behaviour I was expecting

Man, what a relief - and also a learning experience... learnt a bit about programming a machine control board, sanguino, arduino etc and a bit more about leds in the process

Phew - now to move on with putting it all on the machine

I think I will go have a pint or 3 tonight