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[icpcb]

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[MarkF]

I'm a novice at laying out PCBs.  So, can't really help you there.
Dave just did a video review of a members 4 layer PCB that may interest you.

However, I would like to ask you about your software for the ATmega32u4.
I have a discontinued ATmega32u4 Breakout board from Adafruit that I would like to develop an USB interface for.
Mostly, I just need to send block data to the ATmega and have it forward that data to special purpose hardware.
I'm looking at the Arduino IDE and the LUFA library to build the USB stack (thinking I need CDC).
But, I'm having a huge brain blockage trying to figure out how to incorporate the LUFA Library into the Arduino IDE.

(EE degree with 35 years of software development experience here)  Just can't seem to get started.... 

Have you any thoughts on your software development tools related to your USB interface?

Thanks.

[MarkF]

I was only wondering if you were planning on using the LUFA library?

And using the Arduino IDE?

If so, how did you install the LUFA library into the Arduino IDE?
I have been stuck on 'How to install the LUFA library?'

Or, is there a better toolset to develop ATmega32u4 software?

I'm also considering installing the Teensy software since the older boards used the ATmega32u4.


Maybe someone will put fore a direction to pursue for both of us...

[0-8-15 User]

@MarkF, I would try this: https://github.com/Palatis/Arduino-Lufa (scroll down for the installation instructions).

[mayor]

I'd suggest at least a ground pour on the top layer.

[Doctorandus_P]

With uC designs, always make a big as possible GND pour on the bottom layer (or opposite of the layer of the uC).

Then you can also remove the silly GND pad just under the uC, and use that for routing signals, or for a solid power supply distribution for all uC power pins.

The whole PCB needs this GND layer, even under all the buttons.
All the wires to the buttons are antenna's and they pick up external noise (which may be bad enough to disrupt the uC firmware) and they also radiate the noise generated by the uC.

For an example you can look at the GH60 project:
https://kicad-pcb.org/made-with-kicad/gh60/

4-layer boards often have a dedicated layer just for GND. On a 2 layer board you do the best you can.
GH60 for example has GND pours on both sides, and then the top layer is used for horizontal wires, and the bottom for vertical wires. This leaves wide bands for GND on both layers, and these are stitched together with via's.

From an EMC point of view the board is far from optimal.
The most critical section around the uC itself does not have anything resembling a GND plane, and I would have liked to see at least 3 via's in the GND planes for each key to stitch them firmly together.

[mayor]

I'd suggest at least a ground pour on the top layer.

Hi, but should I do a complete layer pour even if the switches don't need it - since they're not grounded - or just around the connected components?

I updated the area around the controller/crystal and moved some components a bit closer. I'm trying to keep it good looking but if it's bad practice on a 2-layer-board I can live without it

Edits:
2020-08-07 12:42:50 pm: Forgot picture MCU Zone.png.

You should try a top pour, among other things, so as to avoid manually routing GND for your decoupliing caps.