# Seeking 4x3 keypad for Atmel UC3 microprocessor

I was doing a combined project with a friend, with me on s/w and him on h/w. After a year of coding on my part & not much activity on his, he announced that he is "too busy" to continue.

That leaves me, a pure s/w guy with little or no h/w knowledge to continue. I need a 4x3 keypad which will work with an Atmel UC3 series 32-bit microprocessor - can you advise?

Preferably something with sample code.

As I have no o/s, should I go interrupt driven or polled? (told you I am not a h/w guy ;-)

Thanks in advance for any help.

• I have an awesome circuit for this... which unfortunately uses an obsolete component (MM74C922). If you can find/pick a decent replacement, I don't mind helping with the rest. – Ignacio Vazquez-Abrams Jan 2 '14 at 3:36
• @IgnacioVazquez-Abrams (+1) That seems to be an interface chip (ebay.com/itm/1pcs-MM74C922N-MM74C922-16-Key-Encoder-FAIRCHILD-/…) I don't mind to buy, but what about the keypad? Long term, of course, I would prefer something that is not obsolete, but I can live with it n a prototype. Thanks for your quick reply. – Mawg Jan 2 '14 at 3:43
• Any 4x4 matrix keypad should do, even those cheap blue and red membrane keypads. Or 4x3, since that's what you're looking for (now that I read it). – Ignacio Vazquez-Abrams Jan 2 '14 at 3:45
• Oopos, yes, I just realize, I only need 10 digits, plus maybe cancel. \$x3 or 4x4, not really important. Do you think that I could just use this device & code? extremeelectronics.co.in/avr-tutorials/… – Mawg Jan 2 '14 at 5:12
• That code/technique will work fine, but require constant polling. The advantages of something like the '922 are 1) interrupt-driven design, and 2) fewer pins (1 interrupt and 4 data [with OE optional, if you want to share the data pins] instead of 4 row and 3 column). – Ignacio Vazquez-Abrams Jan 2 '14 at 5:43

DA connects to an interrupt pin so that the MCU can be notified when a key has been pressed. For 4x3 operation, leave Y4 disconnected (since the Yx pins are sensing).