import time
from machine import Pin

row_idx=[0,1,2,3]
col_idx=[28,27,26,22]

row_pins=[]
col_pins=[]

for i in range(4):
    row_pins.append(Pin(row_idx[i],Pin.OUT,Pin.PULL_DOWN))
for i in range(4):
    col_pins.append(Pin(col_idx[i],Pin.IN,Pin.PULL_DOWN))

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


def key_scan():
    for r in range(4):
        row_pins[r].high()
        for c in range(4):
            if col_pins[c].value()==1:
                print(symbol_table[r][c])
        row_pins[r].low()

while True:
    key_scan()
    time.sleep(0.11)