I have an oddball situation where it would be very convenient to make a small micro-SD-card-like PCB that held something else besides flash memory on the SPI bus. I’m sure I can find the mechanical details and make the “part” myself, but if someone has already done this and it’s publicly available, it’d save some time. I’m using KiCad.
If you’re curious, I have a COTS microcontroller that is currently I/O bound in my system. It can support an SD card, but the vendor doesn’t provide a ready-to-roll library. That’s not a huge deal, I could install Chan FS pretty easy, but OTOH I’d like something not subject to the wear of flash memory. I have a few Everspin Magneto-resistive chips I bought a couple of years ago, and thought this would be a fun application to try them out.
Sparkfun made this inline sniffer board which they have provided Eagle files for.
Eagle files should import into KiCad to let you reuse the microSD outline.
Someone also had one that had emmc pads as well . Can’t seem to find it but I know it was on tindie
Thanks, Eli. This checks all my boxes. Very easy to copy this board outline onto my project.
That was simple enough. I’m curious how this will work.
I wanted to reply to share my design but someone else did it before I could get a chance ( ^^ @eli.hughes )
The only thing you would need to worry about is getting the correct PCB thickness and making sure you have enough length on the PCB to allow for a smooth insertion/removal from a clicky type socket as well as enough clearance around the perimeter.
I would suggest doing a paper print test before ordering the actual PCB, it will give you a good sense of how everything will fit.
I would also like to add it is worth taking care around the little notch. If the SD card holder has the retention mechanism which makes use of the notch, check the minimum router bit radius for your fab process as you may want to cut a little deeper into the PCB to make sure you get the engagement you need. If it’s just a friction fit, who cares?!
@smerrett79 Thanks for that tip. Actually I didn’t know how my microcontroller board socket worked and fortunately I had a spare one here at home. Turns out it is only a friction-fit. And furthermore, it sits so near the edge of the board that about half the uSD card protrudes beyond the edge of the PCB. Knowing this allowed me to shorten my adaptor even more.
I was also worried about physically anchoring an uSD (or uSD-like adaptor). I’ve concluded that in my application, a machine with the size and mass of two industrial refrigerators, and it’s intended use, to log some data like an odometer, if it ever became dislodged because of shock or vibration, the whole machine would be in the process of disintegrating and the uSD card accidentally ejecting would be the least of my worries.