Lots of re-plumbing to make this work, including a bunch of Unicode stuff now in the binary. Bloat City, I'm sure.
TODO: FatFs using unsigned (uint16_t) for UTF16 representation is kinda inconvenient. Lots of reinterpret_cast<>().
API is somewhat stolen from Rust std::fs::File. Static factories didn't work out so well, though. Move semantics made my head explode.
TODO: Still a lot of places where errors aren't handled, but it's an improvement...
Ideally, it'd get pushed back into baseband, and baseband would correct for the length of the packet (based on preamble/access code match timestamp minus preamble/access code duration) to give the exact time the packet started.