I've tried searching in the forum for this, but couldn't quite find an answer for my issue.
I'm using the 12 Button keypad from sparkfun (http://www.sparkfun.com/products/8653) and have no problem wiring it up or reading the key presses from it using the example at http://www.instructables.com/id/Using-the-sparkfun-12-Button-keypad-with-the-ardu/, I've soldered pins into the through-hole mountings and connected it up using a breadboard for testing.
I am monitoring the keypresses using the serial monitor in the Arduino IDE.
When pressing buttons on the keypad, 1,2,4,5,7,8 and 0 all operate perfectly and give consistent readings.
- for some reason gives a #? When I press 3,6,9 or #, I get readings for multiple button presses, e.g. pressing 3 will give a reading for 1 and 3 in quick succession, or sometimes 2,1,3 or any other mix. Similarly when I press 6, I get readings for 4 and 5 also.
I thought I may have crossed two pins with solder, but I reflowed the solder joints and everything looks fine. I also double-checked which pins I put resistors on (I'm using 5.6k resistors) in accordance with the pins in the instructable, I also tried no resistors and with resistors on every pin, the behaviour was still the same.
Does anyone have any suggestions as to what might be the issue here? Am I doing something incorrectly or is there a fault with my keypad?
Any help appreciated. Thanks