@jens With a 210x210 pixel display, the QR code can be of size 22, so you can transport 772 bytes. That should be cheap and simple.
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@jwildeboer @jens just stumbled about this: https://botsin.space/@hackaday/106240302510412897
It's not exactly what you where looking for but maybe still an option? (Reverse engineer instead of real opensource code)
