A fellow and I just had a debate... He claims he has wired a UART's TX directly to a data pin on a USB socket. Then connect that to a comptuer's USB port.
Then he says he ran some magic software on Linux that was able to ingest that UART serial data via the USB pin.
I say it's unlikely - it would take some bizarre bit-banging to receive async UART data wired like this. And I've never heard it being done. This is UART-to-PC via USB but without an FTDI-like chip. Or some way for the PC to get an interrupt due to data transitions on the USB data lines. No USB data frames.
Agree?
On the face of it I completely agree (*see TBH below) but if I had access to this fellow and he made that claim to me I would most likely hassle him until he allowed me to examine the (allegedly) working 'model' of this or admit that he was talking through his hat (and wearing his hat on his bum at the time )
If he made it 'fly' in front of me and in examining it I couldn't find a 'cheat' I would very politely ask him for a squiz at the source code to the 'magic' software he ran on his Linux machine - I'd probably have to apologise to him too, as up to this point I most likely would have been fairly 'rude' about his claim.
TBH: I have studied UART much much more than USB but with my dim-ish understanding of USB I am fairly certain no amount of 'magic' software PC side is going to be able to read anything sent from a UART to a USB port in this way even a bit accurately - that is why I would most likely be rude/mean about his claim till he proved it fairly well unequivocally.
If the UART transmits at a slow baud rate, and if the Linux software had real-time scheduling or ran in the kernel, it might be able to detect each bit the UART transmits as the presence or absence of a connected device. The tricky part would be reliable enough timing, but I'm pretty sure it could be done, at least for slow baud rates.
Oh, the software would also need to prevent sending USB reset conditions in response. More tricky stuff needed, but probably not impossible.
I am familiar with playing unconventional games with USB hardware.....
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