[GreenKeys] ASCII <-> Baudot algorithm

[Mike Willegal]

I recently wrote a very basic RTTY program for the Apple IIe in 6502 assembler, which should be rather easily ported to the Commodore 64.  If I remember right, this one stays shifted on space, but changing it is trivial.  

Conversion is pretty straight forward, you need 3 look up tables. one for BAUDOT to ASCII, one for SHIFTED BAUDET to ASCII, and one for ASCII to BAUDOT.  The only complexity is remembering if you are shifted or not, and remembering to send a shift or unshift before changing state when converting from ASCII to BAUDOT.  I use the highest 2 bits of the ASCII to BAUDOT table to indicate whether is is a shifted or unshifted character or both.

the source code can be found here:  http://www.willegal.net/digitalradio/ttyrx.asm

If you have a terminal unit, you can test your implementation without a radio, using one of the many programs that receive and send RTTY using the sound port of a PC.

regards,
Mike Willegal

PS
this program also sends and receives bit banged serial at 110 baud.