Pico W guess the number: keypad and LCD

# Guess number: press A to start. A secret number from 0 to 99 is picked;
# type a guess and press D. The LCD narrows the range until somebody
# hits the number. Keypad rows on GP21 to GP18, columns on GP13 to GP10.
from machine import I2C, Pin
from lcd1602 import LCD1602
import random
import time

KEYS = ["123A", "456B", "789C", "*0#D"]
rows = [Pin(n, Pin.OUT, value=0) for n in (21, 20, 19, 18)]
cols = [Pin(n, Pin.IN, Pin.PULL_DOWN) for n in (13, 12, 11, 10)]   # pull-downs inside the chip
lcd = LCD1602(I2C(1, sda=Pin(6), scl=Pin(7), freq=400000))

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

secret, low, high, typed = None, 0, 99, ""
lcd.show("Guess number", "Press A to play")
last = None
while True:
    k = key()
    if k and k != last:
        if k == "A":
            secret, low, high, typed = random.randint(0, 99), 0, 99, ""
            lcd.show("Guess %d to %d" % (low, high), "")
            print("new game")
        elif secret is not None and k.isdigit() and len(typed) < 2:
            typed += k
            lcd.show("Guess %d to %d" % (low, high), typed)
        elif secret is not None and k == "D" and typed:
            guess = int(typed)
            typed = ""
            if guess == secret:
                lcd.show("GAME OVER", "It was %d" % secret)
                print("got it:", secret)
                secret = None
            else:
                if guess < secret:
                    low = max(low, guess + 1)
                else:
                    high = min(high, guess - 1)
                lcd.show("Guess %d to %d" % (low, high), "")
                print("between", low, high)
    last = k
    time.sleep_ms(30)

# lcd1602.py: a 16x2 character LCD on a PCF8574 I2C backpack.
# The backpack's P0 is RS, P2 is E, P3 is the backlight and P4 to P7 are
# the display's D4 to D7, so every byte is sent as two 4-bit halves.
import time

class LCD1602:
    def __init__(self, i2c, addr=0x27):
        self.i2c = i2c
        self.addr = addr
        self.light = 0x08
        time.sleep_ms(50)
        for half in (0x30, 0x30, 0x30, 0x20):   # wake up, then 4-bit mode
            self._half(half, 0)
            time.sleep_ms(5)
        self.command(0x28)                      # two lines, 5x8 dots
        self.command(0x0C)                      # display on, no cursor
        self.command(0x06)                      # move right after a character
        self.clear()

    def _send(self, bits):
        self.i2c.writeto(self.addr, bytes([bits | self.light]))

    def _half(self, bits, rs):
        self._send(bits | rs | 0x04)            # E high...
        self._send(bits | rs)                   # ...and low: the LCD reads it

    def _byte(self, value, rs):
        self._half(value & 0xF0, rs)
        self._half((value << 4) & 0xF0, rs)

    def command(self, value):
        self._byte(value, 0)
        if value < 4:
            time.sleep_ms(2)                    # clear and home are slow

    def clear(self):
        self.command(0x01)

    def move_to(self, col, row):
        self.command(0x80 | (col + 0x40 * row))

    def write(self, text):
        for ch in text:
            self._byte(ord(ch), 1)

    def show(self, line1, line2=""):
        self.move_to(0, 0)
        self.write("%-16s" % line1[:16])
        self.move_to(0, 1)
        self.write("%-16s" % line2[:16])