Pico W WiFi weather and time on an I2C LCD

# Real-time weather: join WiFi, fetch the weather and the time, and show
# them on the LCD1602 (I2C1, GP6 and GP7). In Mokxi the weather comes from
# http://weather.mokxi/ and the time from http://time.mokxi/, both on the
# simulated network; the lesson's own program asks OpenWeatherMap and an
# NTP server on the real internet.
from machine import I2C, Pin
from lcd1602 import LCD1602
import network
import time
import urequests

SSID = "Mokxi-Lab"
PASSWORD = "breadboard"
lcd = LCD1602(I2C(1, sda=Pin(6), scl=Pin(7), freq=400000))

def connect(ssid, password):
    wlan = network.WLAN(network.STA_IF)
    wlan.active(True)
    wlan.connect(ssid, password)
    for _ in range(20):                    # give it ten seconds
        if wlan.isconnected():
            return wlan.ifconfig()[0]
        time.sleep_ms(500)
    raise RuntimeError("could not join " + ssid)

lcd.show("Connecting...")
connect(SSID, PASSWORD)

while True:
    r = urequests.get("http://weather.mokxi/")
    w = r.json()
    r.close()
    r = urequests.get("http://time.mokxi/")
    clock = r.text.strip()
    r.close()
    hhmm = clock[11:16] if len(clock) >= 16 else clock[:16]
    lcd.show("%s %.0fC" % (hhmm, w["temperatureC"]), "Humidity %d%%" % w["humidity"])
    print(hhmm, w["location"], "%.1f C, %d %%" % (w["temperatureC"], w["humidity"]))
    time.sleep(10)

# 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])