Atmel – Seeking 4×3 Keypad for Atmel UC3 Microprocessor

atmelkeypaduc3

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 4×3 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.

Best Answer

The circuit I use has the MM74C922 4x4 matrix encoder at its heart. The advantages of using it are that it provides an interrupt for keypress notification plus it handles debouncing the keys.

MM74C922 schematic

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).

Note however that the MM74C92x is obsolete, and supplies will dry up over time. You should look for a more recent part such as the TCA8418 or MAX7360 which, although not drop-in replacements, do offer additional capabilities which may remove some of the burden from the MCU.

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