Interfacing keypad

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Interfacing keypad

  1. 1. Interfacing keypad
  2. 2. What is keypad? <ul><li>In microcontroller keypad interfacing, push buttons are the major part </li></ul><ul><li>Working of a push button is very simple </li></ul><ul><li>Whenever a push button is pressed it conducts and act as a single line, otherwise it act as a open line and conducts nothing. </li></ul>
  3. 3. Scanning of a keypad <ul><li>There are lot of ways in scanning the key pad </li></ul><ul><li>But in all ways the keypad will be consider as a matrix only. </li></ul><ul><li>Rows and columns will be separated and accessed individually. </li></ul>
  4. 4. How a 4x4 keypad looks like??
  5. 5. Scanning concept 1 <ul><li>Ground all column pins by microcontroller programming </li></ul><ul><li>Check the row pins for which row the button is pressed </li></ul><ul><li>Now invert the above operation </li></ul><ul><li>Ground all row pins and check the columns for which column the button is pressed </li></ul><ul><li>Since we have both row and column location it is easy to pin point the location of the key pressed. </li></ul>
  6. 6. 0 0 0 0 Check in microcontroller ??? ??? ??? ??? 1 1 1 0
  7. 7. 1 1 1 0 Given by microcontroller 0 0 0 0
  8. 8. Interfacing with microcontroller
  9. 9. Scanning concept 2 <ul><li>Consider a port and connect all the pins to keypad </li></ul><ul><li>Similar to the concept 1 in this concept also the keypad is going to be in rows and columns </li></ul><ul><li>But unlike grounding all pins in rows and columns, here we are going to ground single pin in row and check every column pin to zero </li></ul><ul><li>It is a lengthy concept but simple one compare to the previous concept.. </li></ul>
  10. 10. Assignments <ul><li>Display the key pressed in LCD </li></ul><ul><li>Define a calculator which can do addition and subtraction operation </li></ul>

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