Yesterday I received my Framework 13, and I already have something in mind to create: an expansion card that can be used to interface UART. The external side of the card would expose a 3- or 4-pin header.
What makes this a bit more interesting is that I’m also considering designing a casing for the expansion that can be attached using N35 magnets (like this). This would allow the IC to be swapped out for something else.
I’d appreciate any suggestions, tips, or things I should watch out for—both on the electrical side and the mechanical design.
The point I make the several times such a card has been proposed is what will be different to using a standard USB-Serial cable? The cable will have a chip that is identical to the ones you’ll need to use in the card, and you need to use a cable anyway to get from the card to whatever you are connecting to, except it needs to be a special cable to match your 3-4 pin header, so if a wire breaks you have to fix it.
With a standard USB-Serial cable you can get a new one if it goes faulty.
I don’t like to pour cold water on someones project idea, but I see no sense in having such a card and then still needing to use a (non-standard) cable to connect to your other device, when a standard USB-Serial cable will do the same job.