from machine import Pin
import utime

keyMatrix = [
  [ "1", "2", "3", "A" ],
  [ "4", "5", "6", "B" ],
  [ "7", "8", "9", "C" ],
  [ "*", "0", "#", "D" ]
]

rowPins = [7,6,5,4]
colPins = [3,2,1,0]

row = []
column = []

for item in rowPins:
  row.append(machine.Pin(item,machine.Pin.OUT))

for item in colPins:
  column.append(machine.Pin(item,machine.Pin.IN,machine.Pin.PULL_DOWN))

key = '0'

def scanKeypad():
  global key
  for rowKey in range(4):
      row[rowKey].value(1)
      for colKey in range(4):
          if column[colKey].value() == 1:
              key = keyMatrix[rowKey][colKey]
              row[rowKey].value(0)
              return key
      row[rowKey].value(0)
  return None


def printKey():
  key=scanKeypad()
  if key is not None:
      print("Key pressed is:{}".format(key))
  utime.sleep(0.2)

while True:
  printKey()