> Bell 202 is an audio FSK modulation at 2200Hz for mark and 1200Hz for
> space. A standard UART stream rides on top of that, at 1200baud.
> I figure encoding is pretty easy (create tables of the sines at the
> right frequencies, and optionally tables for the inverses if you want to
> do continuous-phase FSK). However, I'm pretty clueless about the
> decoding. I've heard about all sorts of different schemes, from counting
> zero crossings (yuck) to fourier transforms, but I haven't been able to
> find a clear explanation that doesn't assume I have DSP knowledge. I
> also need to figure out what the best way for syncing with the UART
> stream is. This is a long-range link (cubesat satellite), so I don't
> expect a perfect radio link.