[GreenKeys] ASCII <-> Baudot algorithm

Sun Aug 2 03:27:47 EDT 2015

very good  to know... how  do we see  we have upshift?   doe  my upi 
teleprinter do that?!?!?

In a message dated 8/1/2015 7:56:00 P.M. US Mountain Standard Time,  
tony.podrasky at gmail.com writes:

Hello  dr;

Well - it gets even a bit worse than that:

Some Teletype  Machines have a feature called "unshift on space"
and some have "stayshift  on space".

"Unshift on space" will take the machine out of the FIGS  when you
receive a SPACE character and downshift it into  LTRS.

"Stayshift on space" will leave it in FIGS when you
receive a  SPACE character.

The difference: you type   QWE 123 123  QWE

If you don't add the appropriate FIGS or LTRS key after the  SPACE
here's what you're going to see:

UNSHIFT: QWE 123 QWE  QWE

STAYSHIFT: QWE 123 123 123

Both have a reason for  existence:

STAYSHIFT was used for PIREPS (Pilot Reports) and was lines  of
groups made of 5 numbers with about 10 groups per line.

UNSHIFT  was used especially for RTTY because when there was static
or fading, the  machine might get stuck in FIGS and you'd have to
translate the numerical  stuff back to text stuff.

SO: when you write your program, you have to  take (that) into
account - so no matter how the data is coming in or going  out,
the message will appear the same.

If you were working with C I  could give you some pointers, but I
don't know anything about a C-64  anymore.

UE,
K2EAA - TONY
NNNN
ZCZC

On 08/01/2015  05:19 PM, drlegendre . wrote:
> Still slogging away at my C-64 TTY  driver project. Only now beginning to
> look into the ASCII / Baudot  conversion issues, and would certainly
> appreciate some input on the  matter.
>
> While ASCII has 128 possible values, Baudot is limited  to 32 which
> doesn't even allow for the full US/Latin alphabet plus the  ten numerals
> - much less punctuation. So it seems that all the  numerals and
> punctuation are 'shifted' characters, using the LTRS and  FIGS scheme.
>
> So when a TTY sends the string "ABC123DEF" it  actually sends:
>
>  LTRS+"ABC"+FIGS+"123"+LTRS+"DEF"
>
> With each printing character  represented in it's 5-bit binary Baudot 
form.
>
> So to implement  a conversion routine, I must not only translate between
> the ASCII  & Baudot values for the chars, I must also know which set the
> char  is from (FIGS or LTRS) and send the correct preamble to toggle the
>  char set prior to the character value?
>
> Do I have this correct?  Are there standard routines / algos for this,
> that I could study? An  example in BASIC would be grand, as that would
> make it so much simpler  on the C-64.
>
> Thanks in advance for any and all comments, you  guys have always been
> great for this stuff..
>
>
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