Raspberry Pi - Wireless network selection with LCD and keyboard

lcd_wifi_connect.py

#!/usr/bin/env python3
import subprocess, time, fcntl, sys
from RPLCD.i2c import CharLCD
from ir.ui import read_key, KEY_UP, KEY_DOWN, KEY_LEFT, KEY_ENTER, KEY_BACKSPACE, KEY_QUIT

LCD_I2C_ADDR = 0x27
LOCK_FILE = "/tmp/lcd.lock"
lcd = CharLCD(i2c_expander="PCF8574", address=LCD_I2C_ADDR, cols=16, rows=2, charmap="A00", auto_linebreaks=False)


def safe_lcd_write(lines):
	try:
		with open(LOCK_FILE, "a+") as lock:
			fcntl.flock(lock, fcntl.LOCK_EX)
			lcd.clear()
			for i, line in enumerate(lines[:2]):
				lcd.cursor_pos = (i, 0)
				lcd.write_string(line[:16])
			fcntl.flock(lock, fcntl.LOCK_UN)
	except:
		pass


def scan_wifi():
	result = subprocess.run(["nmcli", "-t", "-f", "SSID,SIGNAL,SECURITY", "device", "wifi", "list"], capture_output=True, text=True)
	networks = []

	for line in result.stdout.splitlines():
		parts = line.split(":")
		if len(parts) < 2:
			continue

		ssid = parts[0]
		if not ssid:
			continue

		try:
			signal = int(parts[1])
		except:
			signal = 0

		if signal > 0:
			networks.append(ssid)

	return list(dict.fromkeys(networks))


def network_has_config(ssid):
	result = subprocess.run(["nmcli", "-t", "-f", "NAME", "connection", "show"], capture_output=True, text=True)
	return ssid in result.stdout.splitlines()


def connect_existing(ssid):
	subprocess.run(["nmcli", "connection", "up", ssid], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)


def connect_new(ssid, password):
	subprocess.run(["nmcli", "dev", "wifi", "connect", ssid, "password", password], stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)


def is_connected(ssid):
	result = subprocess.run(["nmcli", "-t", "-f", "ACTIVE,SSID", "device", "wifi"], capture_output=True, text=True)
	for line in result.stdout.splitlines():
		parts = line.split(":")
		if parts[0] == "yes" and parts[1] == ssid:
			return True
	return False


def select_network(networks):
	index = 0
	while True:
		ssid = networks[index]
		safe_lcd_write([ssid[:16], "<UP/DOWN ENTER>"])
		key = read_key()
		if key == KEY_UP:
			index = (index - 1) % len(networks)
		elif key == KEY_DOWN:
			index = (index + 1) % len(networks)
		elif key == KEY_ENTER:
			return ssid
		elif key == KEY_QUIT:
			raise KeyboardInterrupt


def enter_password(ssid):
	password = ""
	while True:
		safe_lcd_write([ssid[:16], password[-16:]])
		key = read_key()
		if key == KEY_LEFT: return None
		if key == KEY_ENTER: return password
		if key == KEY_BACKSPACE:
			password = password[:-1]
		elif key and len(key) == 1:
			password += key
		elif key == KEY_QUIT:
			raise KeyboardInterrupt


def connect_flow(ssid):
	while True:
		if network_has_config(ssid):
			safe_lcd_write(["Connecting...", ssid[:16]])
			connect_existing(ssid)
			if is_connected(ssid):
				safe_lcd_write(["Connected", ssid[:16]])
				time.sleep(2)
				return
		password = enter_password(ssid)
		if password is None: return
		safe_lcd_write(["Connecting...", ssid[:16]])
		connect_new(ssid, password)
		time.sleep(2)
		if is_connected(ssid):
			safe_lcd_write(["Connected", ssid[:16]])
			time.sleep(2)
			return
		safe_lcd_write(["Wrong Password", "<- Back"])
		key = read_key()
		if key == KEY_LEFT:
			return
		elif key == KEY_QUIT:
			raise KeyboardInterrupt


def main():
	try:
		while True:
			networks = scan_wifi()
			if not networks:
				safe_lcd_write(["No WiFi found", ""])
				time.sleep(3)
				continue
			ssid = select_network(networks)
			connect_flow(ssid)
	except KeyboardInterrupt:
		lcd.clear()
		sys.exit(0)


if __name__ == "__main__":
	main()