Help with PCB layout, no experience, using ATMega32u4

[dead_pixel_design]

Hey guys,

I have no experience doing this. Just to get that out of the way right up front.

I am following this guide for PCB design: https://github.com/ruiqimao/keyboard-pcb-guide

But this guide walks you through a 2x2 key grid, and I don't know enough about how to expand that to a, in this case, 3x12 grid, specifically what pins on the ATMega32u4 controller I can use for the additional rows/columns

Hoping to get an assist from someone with a little more experience and know-how.

Attached is a screen cap of my layout up to the point where I label the pins on the controller to correspond with my labeled rows/columns on my key grid

[stoic-lemon]

I followed the same guide and posted it in the PCB thread. I got some pretty good advice to think about where each connection was actually going. You have left them floating, but we need to make sure we understand where those capacitors are going to end up being connected to. Good luck and I hope you get some advice from someone who knows about this stuff. I still need advice for my stalled design, too.

[vextanys]

Pretty much any of the unused pins can be used for rows/columns (except AREF) - all are labeled PBx, PCx, PDx, PFx are general purpose digital input/output pins, which the firmware can use for rows or columns. The best pins to use will come down to PCB and package layout.

[TalkingTree]

You can use any pin whose label begins with P. Generally speaking, it's good practice to leave PWM pins for LEDs, if you have them, and I would also strongly recommend to setup a SPI header eventually for flashing your controller, and you can use those pins for your matrix as well, if you need them. Other than that, use whatever pin suits your needs, like being closer to the copper trace etc.

[dead_pixel_design]

You can use any pin whose label begins with P. Generally speaking, it's good practice to leave PWM pins for LEDs, if you have them, and I would also strongly recommend to setup a SPI header eventually for flashing your controller, and you can use those pins for your matrix as well, if you need them. Other than that, use whatever pin suits your needs, like being closer to the copper trace etc.

Thanks for the info TalkingTree, a lot of that is still over my head, but I shouldn't need to take the PMW pins, even though I don't plan on including LEDs at this point. I'm trying to keep it simple, mostly because I really don't have the knowhow at this point.

[TalkingTree]

Just wire the matrix to the controller in the schematic and post the picture here or, better yet, in the living PCB thread. Eventually you'll find a lot of gentlemen with good advices to share.