How does a 4x4 Keypad work with PIC 16f877A?

Replies

• 

  rasu3045

  Hi
  Referred to your circuit
  if B0 is high
  When you pressed Sw1,b4 is high pic input is 0,
  When you pressed Sw2,b5 is high pic refers input is 1,sw3=2;sw4=3
  If B1 is high
  sw5=4; sw6=5; sw7=6; sw8=7.
  If B2 is high
  sw9=8; sw10=9; sw11=A; sw12=B
  If B3 is high
  sw13=c; sw14=D; sw15=E; sw16=f.
• 

  shahrul

  I suggest you to put pull-down resistor at B4-B8 to make that pin low state.
  The explanation, to make row scanning, you activate one row at one time.
  Because of B4-B8 is pull-down, you activate with high signal.
  Ex, ROW1; B0=1, B1=0, B2=0, B3=0
  Then reads B4-B8. If B4 is high, SW1 is pressed; If B5 is high, SW2 is pressed and so on.