I was just typing out my reply, but yours is much more detailed anyway, @OP this is the correct solution.

I’m in no position to discourage you from building this, but this is a fsr greater project than you’re writing it to be. Send me a link to the git repo, so I can tag along and keep updated!

Thanks for the detailed answer, that helps a lot for my understanding.

The project sounds like a lot of work, especially for such a niche application. Do you have a crowd to support this (with time or money) or do you plan pay for this and sell it in the end?

It somehow feels like you put a lot of thought into this already and missed starting from the beginning in this post.

What device do you want to have a USB-C DAC for? What’s the actual size limitations and what power do you want to draw that would need a heatsink? Do you have specs in mind, or is there a comparable project already available to look at?

Then this is not safe.

The maximum charge voltage for a lithium cell is 4.2V while USB will provide 5V. It may work for a while, it may fail in a safe state or something gets hot and burns.

You’re 100% right, I’ve lost ‘i’ somewhere in my debugging process

byte upper_byte = input_bin >> (8+i) ; byte lower_byte = (input_bin >> i) & 0x00FF;

Good idea, I’ve tried usleep after all lines, but no change…

You’re probably right, but that should only change the order of the outputs right?