Hacking a citizen's calculator..???

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".

Clem

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.

Hi Clem,

              I was indeed curious to know the internals of calculators' from citizen or any other company and might land up finding a new protocol for keyboard or display which can be helpful for small embedded systems. I want keypad's and display's protocol/connections/datasheet and will be happy to write the drivers from scratch even for the simple 8 bit controllers. This ready made package might be helpful in implementing the interface devices with controllers.... Out of curiosity in past I started digging up with the calculators.. not much successful in today's date.....

In case you find other good resource do share it...

bye...

Thanks once again for your wonderful replies...

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

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.

Most calculator keypads are just multiplexed matrices, wired directly to the ic.

Hi Samuel,

                Is there any way out which is feasible for digging up into the IC for details... It can be helpful for embedded systems and I can write device drivers from scratch acting as an peripheral for the other microcontroller.

Thanks,

Akshay

Not without a powerful microscope, some nasty chemicals and an excessive knoladge of silicone design. If you can send me few photos of the top and bottom of the board, making sure the vias and traces are visible, then I can try and help explain the design and how to interface it.

I will try to send the good quality pics and try to get IC/part numbers inside,then you may proceed further