----------------snip-------------------------------

> It might seem so, but there isn't any waste.  I've got a grand total of
> three bytes
> left in the rom, and 32 ram. (I did most of the work in the 64, which didn't
> have
> any more ram)
>
> I don't know if it was obvious, but there's a language interpreter in there,
> with conditional
> execution, a PN generator, tons of features. It runs a user program stored
> in EEPROM
>

        I should have looked closer at the language specification.
        I did not realize how many commands had been implemented.


>  I suppose if we ripped out the morse generator, we might be able
> to do it.  The compressed table is 72 bytes (ALL valid chars and prosigns)
> plus the
> table scanner.. I haven't looked at the total size of the routine, but it's
> probably over
> 100 bytes total.  There's a bunch of logic for FM/CW operation, and handling
> the
> interchar space properly.
>
> We'd have to handle the ID issue somehow.
>
        True, the morse routines and tables do take up a good chunk of the
available space in a f84. I was involved in a homebrew repeater controller a few
years ago on an 8031, and the morse routines did take a fair amount of
resources. Of course, if we  got short on space in the 8031 we could just stick
in a larger eprom.


        Back to the f84,
        If all you had to handle was the ID (or other short strings), and since
the transmitter has to be hooked up to proprietary software to program anyway,
why not pre-generate the id string on the pc and just program the eeprom with
the packed dots and dashes. No tables in the pic. The trade off is eeprom
locations versus program space.  I think the worst case scenario is two bytes
per character.

> What's the protocol look like for POCSAG?

        Pretty straight forward. The basic codeword is 32 bits. 20 bits of data,
11 bits BCH ECC and one parity bit. You also have to generate sync words and
idle words.

One online pocsag specification  is available at:
ftp://ftp.demon.co.uk/pub/ham/scanners/POCSAG.TXT

        Another necessity is the ability to transmit true fsk (approx +/- 4.5 kh
z).
Does the agrelo transmitter allow this? Some synthesized transmitters use
phase modulation techniques that make them unsuitable for pocsag.

        I just finished a complete pocsag encoder (512,1200,2400) on a F84. It
just needs an RF transmitter attached. The routines to generate the ECC and
transmit the codewords are pretty simple. Most of the codespace is taken up by
the user interface. ASCII RS-232 to a dumb terminal or pc .
        One of the more annoying tasks was to convert a 7 digit bcd pager
capcode to the 21 bit binary necessary to transmit. I had plenty of code space,
so I used a large slow conventional approach.

        The whole point of all of this is have an inexpensive simple device that
would could signal  contact closures to a cheap, rugged, off the shelf, motorola
beeper, that can be bought for 5 dollars at a hamfest  (and not much more
brand new). Systems like this exist, but they cost too much.

        It just seems that the agrelo device with a (hopefully) simple firmware
update could accomplish this.
        Now, if you also wanted to add ax.25 support then we would  have a
real nifty gizmo :).


If this thread continues I think we might want to change to subject line...



carl

--------------------------------------------------------
Henry Carl Ott   N2RVQ    carlott@interport.net
http://www.interport.net/~carlott/
--------------------------------------------------------
Diplomacy is the art of saying "nice doggy"
until you can find a rock.