Sound Processing Shield for Arduino

As sure as I called the previous PCB layout "final," I came across a solution to a problem I'd seen but not known how to fix: putting the mike input and speaker output into a single cable. (Most applications I can think of for this would have both extended to a single unit, like a headphone with mike, rather than two separate locations.)

Not knowing the standard, I've gone with IN+ on the tip, OUT- on the first ring, OUT+ on the second ring, and IN- on the shield. If I find out the standard for TRRS cables, I'll change it to fit, but that's what it is for now.

To my slight surprise, this also enabled me to move the right-angle headers over to allow a bit more room for them. I might even try to figure out a way to orient them so they're at the edge of the board, rather than pointing across the middle.

All this very nicely frees up a lot of space on the board, so maybe there's some aspect of this that I could add...? (I'm very open to suggestions!)

I got an approximation of how much clearance is needed for the right-angle headers (about an inch, allowing for the space needed when plugging them in), but decided what the heck -- I just gave it as much as I could manage, shoving all of it as far out of the way as I could. I think it's a little over that one inch. I'm not completely happy with putting them in the middle of the board at all, but that's just the way things go.

I'm going to figure on female right-angle headers for the board. Usually I see male headers on manufactured boards, but the exposed leads make me a tad nervous.

Unless someone points out a problem, I'll call this the final version of the board (other than minor edits to increase the efficiency of the traces).

Now to work on that BOM... followed by Gerber files... ack!

I've put several updates on the Fritzing file, but I'm going to wait a bit before I update the graphic.

Among the changes:

1. Adjusted the width and positioning of the leads to the MAX11312, MAX4468, and MCP4462 so there are no shorts or other issues (as determined by Fritzing's Design Rules Check function).
2. Fiddled with several of the traces to make them shorter (saving copper and reducing resistance).
3. Added a Qwiic connector. You can never have too many Qwiic connectors.
4. Also added a pair of 2-pin headers so the mike and speakers can be connected internally. This could be done with short headers, or with right-angle headers.
5. Moved the 24LC32 to allow for the right-angle header on the Mic connector.

I want to do a bit of research (or get a bit of feedback) on how much clearance I'll need for the Spkr connector before I move the NCS2211 (along with C17-18 and R21-22). Once that's all done, I'll update the Fritzing file again, and the graphic with it. (This upload is mainly to make sure that the above changes are backed up!)

Meanwhile, this is looking about ready to figure out the BOM so I can (eventually) send it off for fabrication. I probably should also start figuring out the Python code.

I've uploaded a slightly updated design, mainly with straighter connections (and one completed one that I'd left open before).

I'm still open to any reviews on things, from anyone more knowledgeable than I am (a category which is fairly large).

I've just started this as a replacement for the AudioWing and EchoWing. Helpful comments from those more knowledgeable in electronics are eagerly sought.