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Hacking a citizen's calculator..???

dr.akshay_1980@yahoo.com

I want to know how I can interface the calculator keypad to any of the micro controller and its display with any protocol if possible. Generally these chips are fixed with epoxy glues inside hence its difficult to get the inside IC details.

 

Any help in this regard is appreciated....

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    I would take the serial interface(?) off the keyboard and attach to a converter to USB. The only other worry would to program a HID interface driver. You may get lucky and find a generic one. Just curious, why do you want this? It would not be less trouble, unless you want to "play".image

     

    Clem

  • 0 in reply to clem57

    Good luck finding one that uses a serial keypad, I have opened many calculators in my time and not one has had a serial interface. The only way I can see you reverse engineering it is mannualy following the traces and addind your own micro to interpret the signals. Even then, you would have to replace the screen as those things are a nightmare to hack. Trust me, I am speaking from experience. With all this effort you are probably better off building your own.

  • 0 in reply to kidiccurus

    Hi samuel,

                       I do agree with your response. These things are really nightmare and no more less than solving a brain teaser for me. I tried it tracing the connections even but could not land up successfully in accomplishing that. Might be some other protocol other than serial be there........ who knows....????

     

    Lets hail the reverse engineering methods and start again....

     

    Bye,

    Akshay

  • 0 in reply to dr.akshay_1980@yahoo.com

    Wrist-watches, and typical pocket calculators (not talking about the high end programmable calculators which I don't think Citizen make anyway) have custom chips (since these products are sold in the millions) -  it won't contain a SPI or I2C interface.

    Even if you 'fake' button-presses, I'm not sure it will be useful. The LCD has AC drive (with multiple voltage levels) so you'll need multiple ADCs (one per pin) or clever circuitry to scan the contents of the display to see what got pressed.

    This does not address why you might want to do it, but as you can see, technically it would be hard.

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  • 0 in reply to dr.akshay_1980@yahoo.com

    Wrist-watches, and typical pocket calculators (not talking about the high end programmable calculators which I don't think Citizen make anyway) have custom chips (since these products are sold in the millions) -  it won't contain a SPI or I2C interface.

    Even if you 'fake' button-presses, I'm not sure it will be useful. The LCD has AC drive (with multiple voltage levels) so you'll need multiple ADCs (one per pin) or clever circuitry to scan the contents of the display to see what got pressed.

    This does not address why you might want to do it, but as you can see, technically it would be hard.

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