[GreenKeys] ASCII <-> Baudot algorithm

Sat Aug 1 23:44:55 EDT 2015

I did a little Google and it seems one of our own, Jeff Angus, did just
what I'm attempting some years ago. I just sent him an off-list mail, to
see if he still has the code. Not as if I don't want the challenge, but it
would be neat to so how it's been done in the past (from the 64) - so I can
copy & borrow the ideas as needed.

Are you out there, Jeff?

On Sat, Aug 1, 2015 at 10:38 PM, Whitebear1122 <whitebear1122 at comcast.net>
wrote:

> If I may add my 2 cents as a new member of this group.  All the Model 28's
> that I used in the US Navy in the 70's had unshift on space feature.  As a
> long operator of Navy Fleet Teletype Broadcast, I can understand the
> rationale for it.  Bit errors would miss the LTRS function and result in a
> stuck  line of useless FIGS characters until the typical CR CR LTRS
> function at the end of a line shifted back to LTRS.
>
> 73, Scott WA9WFA
>
>
> On Aug 1, 2015, at 9:55 PM, "tony.podrasky" <tony.podrasky at gmail.com>
> wrote:
>
> > 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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> > --
> > MicroSoft error messages written in Haiku:
> >
> >            A crash reduces
> >        Your expensive computer
> >           To a simple stone.
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