keypad.py

import RPi.GPIO as GPIO
import time

class keypad():

    # CONSTANTS
    KEYPAD = [
    [1,2,3],
    [4,5,6],
    [7,8,9],
    ["*",0,"#"]
    ]

#    ROW         = [26,19,13,6]
#    COLUMN      = [5,21,20]

    ROW         = [37,35,33,31]
    COLUMN      = [29,40,38]

    def __init__(self):
        #GPIO.setmode(GPIO.BCM)
        GPIO.setmode(GPIO.BOARD)

    def getKey(self):

        # Set all columns as output low
        for j in range(len(self.COLUMN)):
            GPIO.setup(self.COLUMN[j], GPIO.OUT)
            GPIO.output(self.COLUMN[j], GPIO.LOW)

        # Set all rows as input
        for i in range(len(self.ROW)):
            GPIO.setup(self.ROW[i], GPIO.IN, pull_up_down=GPIO.PUD_UP)

        # Scan rows for pushed key/button
        # A valid key press should set "rowVal"  between 0 and 3.
        rowVal = -1
        for i in range(len(self.ROW)):
            tmpRead = GPIO.input(self.ROW[i])
            if tmpRead == 0:
                rowVal = i

        # if rowVal is not 0 thru 3 then no button was pressed and we can exit
        if rowVal <0 or rowVal >3:
            self.exit()
            return

        # Convert columns to input
        for j in range(len(self.COLUMN)):
                GPIO.setup(self.COLUMN[j], GPIO.IN, pull_up_down=GPIO.PUD_DOWN)

        # Switch the i-th row found from scan to output
        GPIO.setup(self.ROW[rowVal], GPIO.OUT)
        GPIO.output(self.ROW[rowVal], GPIO.HIGH)

        # Scan columns for still-pushed key/button
        # A valid key press should set "colVal"  between 0 and 2.
        colVal = -1
        for j in range(len(self.COLUMN)):
            tmpRead = GPIO.input(self.COLUMN[j])
            if tmpRead == 1:
                colVal=j

        # if colVal is not 0 thru 2 then no button was pressed and we can exit
        if colVal <0 or colVal >2:
            self.exit()
            return

        # Return the value of the key pressed
        self.exit()
        return self.KEYPAD[rowVal][colVal]

    def exit(self):
        # Reinitialize all rows and columns as input at exit
        for i in range(len(self.ROW)):
                GPIO.setup(self.ROW[i], GPIO.IN, pull_up_down=GPIO.PUD_UP)
        for j in range(len(self.COLUMN)):
                GPIO.setup(self.COLUMN[j], GPIO.IN, pull_up_down=GPIO.PUD_UP)