MicroPython keypad door lock with a servo on an ESP32-DevKitC V4

# Keypad door: type the four-digit code. Each key beeps; the right code
# (1234) turns the servo on GPIO 19 to open the door for a second, and a
# wrong one gives a long beep. The buzzer is behind an S8050 on GPIO 18.
from machine import Pin, PWM
from keypad import Keypad
import time

pad = Keypad([14, 27, 26, 25], [13, 21, 22, 23])
buzzer = Pin(18, Pin.OUT, value=0)
servo = PWM(Pin(19), freq=50)
CODE = "1234"

def angle(deg):
    # 50 Hz is 20 ms a period: 0.5 ms (duty 26) is 0 degrees and
    # 2.5 ms (duty 128) is 180 degrees
    servo.duty(26 + deg * 102 // 180)

def beep(ms):
    buzzer.value(1)
    time.sleep_ms(ms)
    buzzer.value(0)

angle(0)
typed = ""
print("Enter the code")
while True:
    key = pad.key()
    if key:
        beep(50)
        typed += key
        print("typed", typed)
        if len(typed) == 4:
            if typed == CODE:
                print("open")
                angle(90)
                time.sleep(1)
                angle(0)
            else:
                print("wrong code")
                beep(1000)
            typed = ""
    time.sleep_ms(10)

# keypad.py: a 4x4 matrix keypad. Each row is pulled low in turn and the
# columns, held high by pull-ups, show which key joins them to that row.
from machine import Pin
import time

KEYS = ["123A", "456B", "789C", "*0#D"]

class Keypad:
    def __init__(self, rows, cols):
        self.rows = [Pin(n, Pin.OUT, value=1) for n in rows]
        self.cols = [Pin(n, Pin.IN, Pin.PULL_UP) for n in cols]
        self.down = None

    def _held(self):
        for r, row in enumerate(self.rows):
            row.value(0)
            for c, col in enumerate(self.cols):
                if col.value() == 0:
                    row.value(1)
                    return KEYS[r][c]
            row.value(1)
        return None

    def key(self):
        """The key just pressed, once per press, or None."""
        held = self._held()
        if held == self.down:
            return None
        self.down = held
        if held is not None:
            time.sleep_ms(10)           # let the contact settle
        return held