Hey everyone,
i'v come across a challenge of reinstalling a casio calculator and got redirected to using arduinos, i dont have much knowledge about arduinos but i know the basic.
Im tring to reinstall the casio fx-82MS, i'v opened it and saw that the motherboard gets it's input via a silcon keyboard which has metal squares on each key, once u press a key the metal contacts a certain part of the mother board sending a signal to the cpu that u have pressed that specific button(kinda hard to explain).
i want to replace the current mother board with an arduino and write my own software on it, reusing the exterior of the calculator and the keyboard. but i have a problem, i can't seem to find a arduino board that can detect the metal parts from the keyboard.
I'd love for some help from the community to help me find a good board with these traits and also if someone had some tips on how to improve/change the way of reinstalling the calculator(its a unprogramable one).
PhantomRoe:
i'v opened it and saw that the motherboard gets it's input via a silcon keyboard which has metal squares on each key, once u press a key the metal contacts a certain part of the mother board sending a signal to the cpu that u have pressed that specific button (kinda hard to explain).
Not to us, though.
PhantomRoe:
i want to replace the current mother board with an arduino and write my own software on it, reusing the exterior of the calculator and the keyboard. but i have a problem, i can't seem to find a arduino board that can detect the metal parts from the keyboard.
If the button contacts are on the "motherboard" as you term it, then "replacing" it will be a very big challenge.
The metal parts, when pressed, make contact between two wires. Look up "keyboard matrix" and "multiplexing" for understanding how such keyboards (and displays) are handled in code. Find out and write down which key shortens which wires, and sort that into a grid with row and column wires. Typically the row or column wires in pocket calculators also connect to the display, but it should be possible to separate the display from the keyboard. If you want to reuse the motherboard for the display and keyboard, you have to cut all traces to the black lump on it, that covers the original controller. Due to the (relatively) high current required for the display you'll need drivers for both the display rows and columns (digits and segments).
After all that research you know how many I/O pins are required for the keyboard and display. Using dedicated display driver chips and port expanders can reduce the number of pins and other parts considerably. That's one figure for a suitable controller. Next comes the power supply, eventually the battery voltage has to be elevated by an additional step-up converter. Finally the controller should have floating point arithmetic in hardware, else a certain delay between key presses and display update may occur.
The keyboard contacts form a matrix. You will need to trace all the connections back to the calculator microprocessor chip before connecting to the Arduino (google "arduino keypad" to learn how). Remove the calculator chip first, of course.
Why do you want to do something like that? I think this is VERY difficult project. There is many interesting parts and you will probably learn a lot (low power, button matrix, LCD driving) but it is much cheaper to buy a new calculator. I think it is cheaper even when do not include your time in the cost.
OK, so your suggestion of "replacing the motherboard" is nonsense insofar as you are referring to the keyboard. If you were to proceed with this, you would be using that same keyboard. I cannot see any other "motherboard" in those pictures.
That is the absolute least of your concerns. it would be incredibly difficult to use the same LCD display, so you must presume you would be wanting to use a new display and I cannot see that fitting in the same case. I think you are stymied at that point for a start.
In fact, you could not fit any sort of "Arduino" device inside that case either.
Smajdalf:
Why do you want to do something like that? I think this is VERY difficult project. There is many interesting parts and you will probably learn a lot (low power, button matrix, LCD driving) but it is much cheaper to buy a new calculator. I think it is cheaper even when do not include your time in the cost.
I'd like to do it for learning purposes mostly, in addition im a student in school so having a calculator with some extra functions is always nice
Paul__B:
OK, so your suggestion of "replacing the motherboard" is nonsense insofar as you are referring to the keyboard. If you were to proceed with this, you would be using that same keyboard. I cannot see any other "motherboard" in those pictures.
That is the absolute least of your concerns. it would be incredibly difficult to use the same LCD display, so you must presume you would be wanting to use a new display and I cannot see that fitting in the same case. I think you are stymied at that point for a start.
In fact, you could not fit any sort of "Arduino" device inside that case either.
I'v understood that the motherboard and keyboard are one peice when i opened the calculator all the way and took the images(after posting the original thread).
I'd be open for anyone's idea on how i could insert or reinstall the calculator(with out buying another one, already have other ones, this is for learning purposes and experience). Money and time aren't and issue for me so im open for a wide range of options
