Re: A82: Checksums and modules
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Re: A82: Checksums and modules
The program included with ash 3.0, I think, fix.com will change the checksum of
a hacked 82p file to one that will be accepted in the graph link as you require.
It is on Doug Torrance's (I think) hacking the 82 page, too.
RLE compression works pretty well for b+w bitmaps, or any other redundant stuff,
and its very simple to implement. Basically, you have a pattern, then how many
times to repeat it. Ex:
000000001111
could be 0, repeat 8;1 repeat 4. In ti-basic, you could use a matrix and store
it as [0.8 1.4], or in a list. I think it is what was used in the compress
routines for the 85, those could be help. Its a pretty simple algorithim thats
good for picts, especially on the 82, cause the decompression algorithm is
really simple.
Thomas J. Hruska wrote:
> At 07:37 PM 10/21/97 EDT, you wrote:
> >In a message dated 97-10-21 18:46:12 EDT, you write:
> >
> >> SQRXZ for the 86 has the ability to add on modules. I want to have the
> >> same ability in the 82 version. I know how to create a checksum to find
> >> such modules, but I don't know how an 82p file is laid out. Especially
> the
> >> checksum that is changed so that the calc will accept the program. I
> don't
> >> want the levels to appear in ASH but only in the PRGM delete menu and
> >> inside SQRXZ itself. Any help is appreciated.
> >
> >Well, if the first byte of a level is anything but $00, it will not show
> up in
> >the Ash menu. I recommend using a different value, such as $26, $2C, $63,
> >$7E, $AA, $BB, $EB, or $EF. Those are all the values not used by the
> >calculator.
> >Good Luck,
>
> Sorry I didn't make myself clear the first time. What I'm asking is how to
> figure the checksum the calc uses to determine if a PRGM is okay to accept
> through the link cable. Also, how would you go about reserving and
> removing space in the RAM for modules such as these? I want to be able to
> create levels on the 82, compress them, and then use my link cable to
> transfer them between computer and calc.
>
> BTW, can anyone give me a list of compression algorithms that have been
> used for the 82 (and how well they do it)? My best algorithm can currently
> compress 50 bytes (SQRXZ world) down to 11 bytes (78% compression) using
> PCX bitmap style compression.
>
> Thomas J. Hruska -- thruska@tir.com
> Shining Light Productions -- "Meeting the needs of fellow programmers"
> http://www.geocities.com/SiliconValley/Heights/8504
> http://shinelight.home.ml.org
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