Electronics > Microcontrollers

help with HP 35s

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dilbert:
Hello everybody,this is my first post.
I write as a user of Hp calculators,in particular of the new 35s
http://en.wikipedia.org/wiki/HP_35s
It is a great calc,but it misses three big things:
-a dozen-plus list of bugs
-no I/O whatsoever,so you cannot update/hack/fix it
-2032 instead of AAA batteries

This the teardown:
http://i.cmpnet.com/embedded/2008/February08/0208esdTDNass02.gif
http://www.finetune.jp/~lyuka/interests/calc/hp35s/

It uses a modern 8502 made by Sunplus Tecnology(SPLB31A),but i also get references to Generalplus GPLB31A.
Datasheet:http://www.generalplus.com/products/lcdcontroller/datasheet/GPLB31AV14_ds.pdf

Now,as the datasheet says there should be a serial-RS232-compatible Tx/Rx couple of pins(I'm sorry i a have an IT background,not an electronic one) coming out of the chip,right?
Where are they in the board?Can this thing be hooked up to a pc?It will make hundreds of users very,very,very happy.
Thanks guys,
Nicola

alm:
Not much point in connecting to the UART pins if the firmware does not support it, the firmware will have to configure the UART and do something with the data. If the firmware supports it and the pins are not used for something else, connecting it to a PC via a logic-level (3.3V?) to UART converter should be fairly straightforward.

dilbert:
I forgot the firmware.Who knows.Only HP does.
Where are on the board those pins?Thanks

Zero999:
Just read the Wikipedia link.

I have an old HP 35 I got from an office clearout at work a few years ago. I wonder how much it's worth? Not that I'm selling it any time soon..

EEVblog:
If Cyrille didn't bring the RS232 pins out the pads on the board for troubleshooting et.al then it's likely the firmware does not have any UART capability at all. In which case it's pretty pointless to try I think.

Dave.

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