Re: TI-H: EEPROMS
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Re: TI-H: EEPROMS
From: "Simon Trimble" <gingerno1@hotmail.com>
> That sounds like a V good idea. Im sure someone could interface a PIC
micro
> to on of these and have it as a "saved game" device so that you can keep
> your high scores etc indefinately, insted of having to back them up to a
PC
> every day in fear of a calc crash and/or reset! (not a problem though if
> your calc saves them when they are archived).
If I were implementing an expander, I would use a largish AVR (8535 most
likely, because it has lots of room for code and is quite versatile,
allowing hacker types to do things like attach lots of analog or digital
sensors without having to add additional microcontrollers to the system. It
includes an onboard RTC (IIRC).
Attach some memory (I'd probably use serial EEPROM) for storage, then, most
importantly, write the software such that it could operate as if it were
another calculator on the link port. In this mode you could use the
expander to initiate a transfer to send custom drivers to the calculator.
Or you could do something tricky like send a variable to the expander
containing a number that identifies a piece of data to transmit to the
calculator. Upon receiving the variable, the expander would then transmit
back the selected item. A request of a special item would result in the
transmission of a string containing a listing of all the available items.
This would allow the expander to operate without drivers or a shell of any
sort. Optionally a second mode could be included to allow more direct
communication with a driver program (which can allow faster transfers).
Given my predisposition to internal hardware, I would be inclined to design
it such that it could be mounted internally so I could use one of its IO
pins to drive the calculators main clock input to allow for features such as
accurate timing on the calculator, software configurable turbo functions and
just MAYBE, a multiplexed color display via the use of R, G and B LED
backlighting.
Unused port pins and the ISP pins could be brought out of the calculator
case on a mini-header to allow for external devices and reprogramming of the
AVR.
DK
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