Hello @atk90x ,
You can upload files on devices as a part of firmware functionality, but your question is really about playing them rather than uploading.
Currently we support WAV playback from patches written in C++ and in FAUST. It’s very likely that PD/gen~ will get support for this eventually too.
As you probably have realized, we can’t use the same PD environment that runs on desktop, but rather a compiler called Heavy (HVCC), since it has to run on a microcontroller. That compiler was developed by third party as a closed source product, abandoned and published under open source license later. We’re using a forked version of that that adds some feature that OWL needs, but there’s no active development going on our side. However, upstream HVCC was later picked up by another developer who is on forum here - @dreamer . There’s currently some ongoing work that would allow us to switch to his fork of HVCC. I think that there’s a good chance that WAV playback could be added after that.
I would add that we’ve discussed this a bit in the past and WAV playback is likely the most wanted addition to PD. Currently you have 8 Mb of external flash that could be used to store files. But we’ll probably add support for reading for files from USB drives too.