Any spare GPIO ports available for interfacing?

K8200 3D Printer K8200 - Wiring and electronics
1

Hi all,

Does any one know if there are any resources, perhaps posts that show any GPIO ports from the AT2560 which are unused by the rest of the printer but are available on a header (happy to solder a little if necessary and pay for new board if I mess it up).

I’d like to interface the board with another Arduino or pi as I am having good success with hacking linear position sensors (read cheap digital calipers). I have them talking to an arduino which is doing some processing and my plan was to attach two to each end of the extruder support. If I can get the AT2560 to talk to the second arduino via a gpio, or if there were enough gpio pins to talk to the hacked calipers directly, then I could gain some incredible accuracy with the z-axis.

Reason: After 2.5 years (I think) of ownership I have just upgraded my 8200 with the 0.35mm extruder + z-axis superior screw kits which are superb and working beautifully. However I still I find the bigest impact on quality is imperfect z-axis control, with +/-0.01mm external measurement and feedback of the height both ends of the extruder support I think I could get a VERY reliable setup. Also, it will be fun!

Any help would be gladly appreciated, even if just a layout of the PCB of the 8200 controller board with any exposed GPIO pins would be fantastic. The reason I think some connections on the pcb must have been hooked up to the arduino chip is that there is an LCD kit which I believe uses them, but perhaps it communicates via something other than simple GPIO ports, so apologies if I’m wrong and have wasted your time reading all this!!

Thanks,
Danny

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For a schematic and description of the controller look here : reprap.org/wiki/3Drag_controller

But, i don’t want to disillusion you, those “cheap” calipers aren’t nearly 1/100th mm in precision…

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Whilst the absolute accuracy of the cheap capacitive scales is not all that brilliant, the resolution is good.

The update rate is rather slow and you’re likely to run into control loop stability problems if you try and do a closed loop movement.

There are nearly always ‘hidden’ modes in the calipers that can be activated via the data connector. One of these is a fast update mode, but it’s still pretty slow.