Member Since: November 2, 2009

Country: United States

  • I just got this keypad and wired it up to an Arduino Duemilanove. I followed the instructable linked above ( and am having some weird problems.
    I’m using the sample code provided in the instructable that outputs the characters of any button pressed to serial. It often prints two characters for a button that I only press once. For example, if I press each button once it should print out 1234567890# but it might print 1234456778990#. It doesn’t seem to be a specific button, as I can sometimes push each button and get the correct output, but usually there are some errors. I can get duplicate characters with any button, too. The duplicate character, when it shows up, seems to come from releasing the button.
    I’ve tried wiring it up using 1k resistors between pins 4, 6, 7, and 8 on the keypad as directed in the instructable and without and resistors, and I get the same behavior. Do I need resistors? I’m not exactly an electronics expert, but I’m slowly learning.
    Does anyone have any ideas what might be wrong?