Re: PIC Expander

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Re: PIC Expander

Michael J. Malluck wrote:

> Hi, YOU GUYS!!!
>         The light bulb turned on and an idea struck me (ouch!). The
> TI-graphlink uses a pic controller to turn computer signals to TI link
> signals. It wouldn't be to hard (correct me if I'm wrong) to get the
> commands out of the pic controller. Then alter them to your liking and

Well, actually, it isn't very easy either. Most PICs have protection
bits,
and the only way to read anything in the memory is to turn these bits
off.
However, doing so will erase the program - Leaving you with a worthless
graphlink. Some people have hacked a way to get by code protection on
the
PIC16C84, however, I strongly doubt that the graph link uses this part.

Even if you can get a dump from the PIC (which I doubt) you still need
to
decompile the dump, a tedious and painful process at best.

> put them into another pic controller (if you had the right, expensive
> equipment). Using these comands one could make a Mem Expander that would
> use link protocal and be able to send backups back and forth (someone has
> already thought of this and is working on such an expander (aprox. 40-50
> for the 512k unit)). Using such a controller any type of unit could be
> attached to the TI with little (if any) driver software.

If you're talking about the Extender uP
(http://www.flash.net/~bryanr/extend/)
then yes, it is possible to use the TI link protocol (as I am doing.)

However, the TI protocol is fairly inefficient, and rather slow. I am
hoping
to get 5k/sec, but I'm not making any predictions. I will probably need
to
make a custom protocol for transfers, and then use the TI protocol only
for
backup transfering. Remember, however, that noone knows if backup
transfering
is possible from a small microcontroller. I tend to think it is. In any
case,
we'll see in a few weeks when I build a prototype.

BTW, I will not be using any source from the graph link. It's too
difficult
to get the code out of the PIC, and there would be legal issues, even if
I
did. It's just much easier to rewrite the code myself. Knowing TI, the
code
inside the PIC probably isn't all that optimized, anyhow.

Regards,

Bryan Rittmeyer
bryanr@flash.net
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