nsec-badge VS EmbeddedProto

All the source files are open and available on Northsec's Github: https://github.com/nsec/nsec-badge/tree/master/hw/2023/hardware

Step zero is to decide how is your board going to be assembled. Do you feel confident enough to solder and assemble everything yourself or would you defer some of that job to a manifacturer. If you go with a manufacturer, check how they get their parts supply, that will limit which parts you can select. For example, jlcpcb offers a manufacturing service for board assembly, but the parts have to come from lscs. Then the first step is selecting the parts required. This one is currently quite tedious because there's a big part shortage. The bigger costier chips first as everything else will fall around that. In this case, we're looking for the microcontroller and the codec chip, then the power supply chips. I'd choose the microcontroller first as it's an easy but laborious step. You want a chip that has at least all the peripherals you need and make sure that they're not conflicting: some peripherals might block another from being used in certain places. It's a bit of a puzzle to solve. In this specific case, we'd want at least some i2s peripheral and an sdio too, i2c or spi for the screen, with some left over pins and some decent amount of flash that can also be user configured. Next the codec which will require some interface compatible with the microcontroller. For the power supply, i copied the design from a board i already worked on i was board tested and known to work: the 2019 nsec badge

Have you looked into Embedded Proto? https://embeddedproto.com/

For a general embedded library for safety critical applications you could look at our Embedded Proto lib. This is a data serialization lib which is checked against the MISRA coding standard guidelines. Doing so makes it possible for our customers to use it in medical applications.

That's when protobuf has your back if other formats don't.

Embedded Proto is a project aimed at using protobuf with embedded C++ code without using dynamic memory allocation. It is MISRA compatible code and build with professional use in mind.