Storing data on micro cassette (Patreon)

Those who are watching the streams on bitluni live or twitch might be up to date on the latest abomination from the lab. Yet, I wanted to sum up for those who don't have the time to watch me suffering for hours and hours. Apparently, there is a lot to learn about data encoding on analog media. We tried amplitude modulation on 9 parallel frequencies which turned out to have limited density. But in the end I went for the C64 datasette solution which is more robust towards analog tape oddities. FSK frequency shift keying uses a certain frequency for 1 and double the frequency for 0. One or two waves per bit are enough to reliably store a bit. Here is the prprof

oof:

On yesterday's stream we got the breakthrough by adjusting the sync each byte by a few samples. That helped a lot and you can see in the console on the right all 32 bits were restored with great confidence.
My next steps is to optimize this a bit so it can run on the MCU while streaming the audio simultaneously. Then the only thing left is to put it an a case that resembles the C64 datasette (but tiny) and the project is done.

This project touches so many engineering topics that it can only end up being an interesting video.

So please stay tuned and thank you for your support!