Raspberry Pi - Read all USB input devices with keyboard capabilities

ui.py

import sys
import termios
import tty
from evdev import InputDevice, list_devices, categorize, ecodes
from select import select

# Key constants
KEY_UP = "UP"
KEY_DOWN = "DOWN"
KEY_LEFT = "LEFT"
KEY_RIGHT = "RIGHT"
KEY_ENTER = "ENTER"
KEY_QUIT = "QUIT"
KEY_BACK = "BACK"
KEY_BACKSPACE = "BACKSPACE"


class InputReader:
	def __init__(self):
		# Get all USB input devices with keyboard capabilities
		self.devices = {}
		for path in list_devices():
			device = InputDevice(path)
			capabilities = device.capabilities()
			# Only monitor devices with keyboard keys
			if ecodes.EV_KEY in capabilities:
				self.devices[device.fd] = device

		self.stdin_fd = sys.stdin.fileno()
		self.old_settings = termios.tcgetattr(self.stdin_fd)

		tty.setraw(self.stdin_fd)

		if self.devices:
			print("Monitoring USB input devices:\r")
			for device in self.devices.values():
				print(f"  - {device.name}\r")
		print("Also monitoring SSH keyboard input\r")

	def __del__(self):
		try:
			termios.tcsetattr(self.stdin_fd, termios.TCSADRAIN, self.old_settings)
		except:
			pass

	def read_stdin_key(self):
		ch = sys.stdin.read(1)

		if ch == "\x1b":  # ESC
			ch2 = sys.stdin.read(1)
			if ch2 == "[":
				ch3 = sys.stdin.read(1)
				key_map = {
					"A": KEY_UP,
					"B": KEY_DOWN,
					"C": KEY_RIGHT,
					"D": KEY_LEFT,
				}
				return key_map.get(ch3)
			return KEY_QUIT

		if ch in ("\r", "\n"):
			return KEY_ENTER

		if ch == "\x7f":
			return KEY_BACKSPACE

		if ch.lower() == "q":
			return KEY_QUIT

		# Return any printable character as-is for text input
		if ch.isprintable():
			return ch

		return None

	def read_usb_key(self, fd):
		device = self.devices[fd]

		for event in device.read():
			if event.type == ecodes.EV_KEY and event.value == 1:  # Key down only
				key_event = categorize(event)
				keycode = key_event.keycode

				# Handle key codes (can be string or list)
				if isinstance(keycode, list) or isinstance(keycode, tuple):
					keycode = keycode[0]

				key_map = {
					'KEY_UP': KEY_UP,
					'KEY_DOWN': KEY_DOWN,
					'KEY_LEFT': KEY_LEFT,
					'KEY_RIGHT': KEY_RIGHT,
					'KEY_ENTER': KEY_ENTER,
					'KEY_KPENTER': KEY_ENTER,
					'KEY_Q': KEY_QUIT,
					'KEY_ESC': KEY_QUIT,
					'BTN_RIGHT': KEY_ENTER,
					'KEY_BACKSPACE': KEY_BACKSPACE,
					'KEY_DELETE': KEY_BACKSPACE,
				}

				result = key_map.get(keycode)
				if result:
					return result

				if isinstance(keycode, str) and keycode.startswith('KEY_'):
					key_char = keycode.replace('KEY_', '')

					# Single letter keys (A-Z)
					if len(key_char) == 1 and key_char.isalpha():
						return key_char.lower()

					# Number keys on main keyboard
					if len(key_char) == 1 and key_char.isdigit():
						return key_char

					# Number pad keys
					if key_char.startswith('KP') and len(key_char) == 3:
						return key_char[2]  # KP0 -> 0, KP1 -> 1, etc.

					# Handle special characters
					char_map = {
						'SPACE': ' ',
						'MINUS': '-',
						'EQUAL': '=',
						'LEFTBRACE': '[',
						'RIGHTBRACE': ']',
						'SEMICOLON': ';',
						'APOSTROPHE': "'",
						'GRAVE': '`',
						'BACKSLASH': '\\',
						'COMMA': ',',
						'DOT': '.',
						'SLASH': '/',
						'KPASTERISK': '*',
						'KPMINUS': '-',
						'KPPLUS': '+',
						'KPDOT': '.',
						'KPSLASH': '/',
					}

					if key_char in char_map:
						return char_map[key_char]

		return None

	def read_key(self):
		while True:
			read_fds = list(self.devices.keys()) + [self.stdin_fd]

			r, w, x = select(read_fds, [], [])

			for fd in r:
				if fd == self.stdin_fd:
					# SSH keyboard input
					result = self.read_stdin_key()
					if result:
						return result
				else:
					# USB keyboard input
					result = self.read_usb_key(fd)
					if result:
						return result


_input_reader = None


def read_key():
	global _input_reader
	if _input_reader is None:
		_input_reader = InputReader()
	return _input_reader.read_key()


# Set of command strings that are not printable characters
_COMMANDS = {KEY_UP, KEY_DOWN, KEY_RIGHT, KEY_LEFT, KEY_ENTER, KEY_QUIT, KEY_BACKSPACE}


def read_text(lcd, prompt):
	text = ""

	while True:
		if len(text) <= 15:
			display_text = (text + "_")[:16]
		else:
			display_text = text[-16:]

		lcd.write(prompt[:16], display_text)
		key = read_key()

		if key == KEY_QUIT:
			return KEY_QUIT

		if key == KEY_LEFT:
			return KEY_BACK

		if key == KEY_ENTER:
			if text.strip():
				return text.strip()
			continue

		if key == KEY_BACKSPACE:
			text = text[:-1]
			continue

		if key and key not in _COMMANDS and len(key) == 1:
			text += key


def format_name(name: str) -> str:
	name = name.replace("_", " ").replace("-", " ").strip()
	if len(name) == 2 and name != "on":
		return name.upper()
	return name.title()