[GreenKeys] Feeding ITTY to the teletype; simulating M33/35 teletypes hooked to computers like in the 70s

[Paul Heller]

On Aug 28, 2012, at 9:35 PM, epvgk at limpoc.com wrote:

> Not sure how much help I can be, but a friend and I wrote some C code that 
> can successfully decode ITTY audio into binary data using the fast fourier
> transform, and also code to decode the binary data into a baudot stream
> and/or convert it to ascii. You're welcome to that if it will help. 

Please send it along, Eric.



> 
> It seems totally plausible to me. Assuming you can get internet access 
> preconfigured (does it use Wifi? or just ethernet?)

Just ethernet for the Beaglebone. I don't know about the Raspberry Pi yet.

> you should be able to
> make it work with some variant on my FFT processor and the standard linux
> utilities. I don't know anything about how you would toggle an output line
> from linux in realtime to key the TTY loop, but possibly if the board has
> a suitably flexible UART you could just send the decoded baudot characters
> to that and let it handle it. That would also let you do additional tricks
> like have it decode a 45 baud signal from ITTY and output a higher speed
> signal, or ascii :) 

The board does have a UART. Your idea of basing this on your FFT process is a very good one. Why didn't I see that? So there seem to be some options. 
> 
> Another possibility, if you want to keep it simple, is just set up the PI
> or beagleboard to stream ITTY over the internet and output audio, and then
> depend on an external demodulator to actually decode it and feed the tty
> loop. 

Yes, this would be a simpler faster approach and easier to start with before progressing deeper

Thanks for your thoughts and suggestions, Eric.

Paul