[GreenKeys] USB to TTY-loop possibility...

[epvgk at limpoc.com]

It seems like lots of folks have been looking for an easy solution to 
connecting a computer to a TTY loop... There are various options like 
reprogramming the CP2102-based usb-serial adapters and using PC software
to generate the baudot code for it. 

I just picked up a little breakout board for an Atmel cpu (Atmega32u4)
which is tiny and has USB support builtin. The whole board is only like 
3/4" by 1" and costs $16.  I've been playing around a bit writing software
to make it act as a complete USB to TTY adapter...

The idea is to make it look to the computer like a generic USB serial device,
but internally handle all the character set conversion, shifts, and framing,
and without a large internal buffer. So you talk to it from the computer
in ASCII and it ignores whatever the computer thinks about baud rate, character
size, etc, and produces correctly timed 7.42 code at 45.45 baud on the output
end, and vice versa for receiving. It only picks up a new character from 
the computer when it's done sending the current one to the loop, to avoid
having to wait for a buffer full of data to transmit once you stop sending.

Anyway, it's nowhere near finished but i have the sending side more or less
working as a proof of concept at least... if I can get it working well I'll 
make the software available and anybody who wants to can get one of the boards
and program it with my code... just thought I'd mention it in case anyone is
interested, and to motivate myself to make time to finish it :) 

eric