Delan Azabani

Hacking the Casio fx-82MS

The fx-82MS is a cheap two-line scientific calculator that I fondly remember using for countless hours since the beginning of high school. It's so reliable that after using the same one for over six years, the worst that's happened is a bit of corrosion on the rear screws. Here are a couple of useful tricks I've found after digging through forums and videos.

Upgrade your calculator to an fx-570MS

Casio's two-line scientific calculators all appear to use the same circuit board and firmware. A combination of several soldered contacts determine which features of the firmware to enable by default. A pencil can be used to permanently change the effective model on older hardware revisions, but this has since been prevented with a hard black obstacle injected onto that area of the board.

You can also 'upgrade' your calculator to an fx-570MS, which is one of the most feature-complete and expensive Casio scientific calculators by exploiting an overflow bug, which lasts until the next reboot.

  1. Enter standard deviation mode, by pressing [MODE] [2].
  2. Press [0], then press [M+] until the words "Data full" appear on the screen.
  3. Press [M+] [2] [UP].
  4. Press [1] [3] repeatedly until no more can be entered.
  5. Press [=]. You will see the words "Data full".
  6. Press [=] [0] [1] [AC].

With a few caveats, the available modes should be expanded to:

Of particular note is an an image of the fx-570MS, which will become very useful for you when you need to find a key, because although the key layout will be the same as on your calculator, the labels will not be.

Diagnostic routine

This is a capability built into the firmware, presumably to allow easy, initial in-factory testing of the screen and keypad. At any time during the routine, pressing [ON] will reboot the calculator, ending the test.

  1. While holding [SHIFT] and [7] down, press [ON]. The display will turn on all of its elements.
  2. Press [SHIFT]. The display will clear completely.
  3. Press [SHIFT]. The display will turn on half of its elements in a pattern.
  4. Press [SHIFT]. The display will turn on the other half of its elements.
  5. Press [SHIFT]. On the first line of the display, you will see "25" on the left, and "4" on the right. On the second line of the display, you will see all zeroes, including in the exponent.
  6. Press [SHIFT] nine times. The display will cycle its second line through all ones, then all twos, and so on, until the second line consists of all nines.
  7. Press [SHIFT]. The display will clear and the second line will be set to "0". This commences the keypad testing routine.
  8. Press the keys of the keypad in the order,
    [SHIFT] [ALPHA] [MODE] [LEFT] [UP] [RIGHT] [x-1] [nCr] [Pol(] [x3] [DOWN]
    then the rest of the keys, as you would read them left to right, until [=]. On the first line of the display, you will see 25 on the left, and OK on the right. On the second line of the display, you will see 4.
  9. Press [ON] to reboot the calculator and exit the test.