I am hacking an old TI-30 calculator. It wired up the positive voltage of the keypad and the LED matrix together. How can I read the voltage with a MAX7219 LED Driver and a 74HC595 shift register?
I know that the key presses on a calculator will be relatively long so I think that I could shut off the MAX7219(through arduino pin or transistor?) and pulse the matrix for keys, then repower the MAX7219 and resend it data.
Driving a led segment and keypad?
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
Please be positive and constructive with your questions and comments.