# Matrix Keypad
# NerdCave - https://www.youtube.com/channel/UCxxs1zIA4cDEBZAHIJ80NVg - Subscribe if you found this helpful.
# Github - https://github.com/Guitarman9119

from machine import Pin
import utime

inKey = ""

# Create a map between keypad buttons and characters
keyMatrix = [['1', '2', '3', 'A'],
               ['4', '5', '6', 'B'],
               ['7', '8', '9', 'C'],
               ['*', '0', '#', 'D']]

# PINs according to schematic - Change the pins to match with your connections
keypadRows = [9,8,7,6]
keypadCols = [5,4,3,2]

# Create two empty lists to set up pins ( Rows output and columns input )
colPins = []
rowPins = []

# Loop to assign GPIO pins and setup input and outputs
for x in range(0,4):
    rowPins.append(Pin(keypadRows[x], Pin.OUT))
    rowPins[x].value(1)
    colPins.append(Pin(keypadCols[x], Pin.IN, Pin.PULL_DOWN))
    colPins[x].value(0)

def scankeys(): 
    keyPress = ""
    for row in range(4):
        for col in range(4):
            rowPins[row].high()
            key = None

            if colPins[col].value() == 1:
               keyPress = keyMatrix[row][col]

        rowPins[row].low()
        
        if keyPress != "":
            utime.sleep(0.2)

        global inKey
        inKey = keyPress
       
while True:
    scankeys()
    
    if inKey != "":
        print(inKey)