nanopb VS jems

While I don't have much experience with it directly, I do know that Google's protobuf was designed with minimal footprint capabilities in mind. While it might not work out-the-box for embedded systems, it looks like there is a well maintained open source library NanoPB that "is a small code-size Protocol Buffers implementation in ansi C. It is especially suitable for use in microcontrollers, but fits any memory restricted system." And for added reassurance, it looks like Chromium has a dependency on NanoPB.

nanopb

Protocol buffers are designed for this. Consider using nanopb on the device side.

I think you're looking for nanopb, the lightweight implementation of Google's protocol buffers.

In that runtime environment, using only C is indeed the (very) safe "bet". In particular, I might personally prefer using Nanopb - Protocol Buffers for Embedded Systems.

I know it’s not the question you asked, but the answer might be this: https://github.com/nanopb/nanopb

The OTHER way to do it is with protobufs, since they don't encode parts of the message that aren't included (that is: any missing part of the message has 0 transmission overhead). nanopb works well on the ESP32.

You could look at my library Embedded Proto and Nanopb. If you have any questions let me know.

After reviewing several options, I’ve settled on plain old JSON. For parsing, I use https://github.com/zserge/jsmn. For serialization I use https://github.com/rdpoor/jems (disclaimer: I wrote the latter, but others use it as well).

By contrast, jems (Json EMitter Stream) emits characters on the fly rather than building up a large data structure, so it uses very little memory. The only storage requirement is a few bytes for each nesting level, which normally doesn't get that deep.