I'm trying to hack a CASIO fx-85ES calculator:
I want to use the calculator as a keypad (arduino knows what button you pressed) and display (arduino "presses" a button), using an Arduino Pro Mini (5v).
buttons are pressed by connecting two contact points on the board:
for example: K07 + KI5 = "1" or K01 + KI2 = "4"
I only want to use the following keys: 0-9, +, -, x, :, =, and ")". total of 16 buttons
I plan to:
Connect points using transistors "press buttons". (is there a way the arduino can do this without transistors)
Use pins as input to read buttons pressed. (or more transistors?)
Note: I will only use calculator as INPUT OR OUTPUT never both at once.
Anything I forgot or suggestions? what do you think, could this work?