title: Logic for 9 key keyboard to print qwerty keys
body: <p>I have a device which has got 9 keys just like an ordinary mobile phone.
  I want to print normal alphabets like ABCD using these 9 keys exactly the way mobile phones let you do it. </p>
  
  <p>This is an embedded system programming project. I am unable to figure out the logic to implement this functionality. </p>
  
  <p>I am detecting keys by polling and not by interrupt.</p>
  
  <p>Can someone help? I will appreciate if you can point out  related resources as well. </p>