Relay control

main.py

import curses
from curses import wrapper
import serial
import sys

channels = ['1', '2', '3', '4', '5', '6', '7', '8']

def calc_crc(data):
	return sum(data)

def enable_relay(id, state):
	state = state | (1 << (id - 1))
	return state
	
def disable_relay(id, state):
	state = state & (~(1 << (id - 1)))
	return state

def init_protocol():
	# 1 (0x55) - head
	# 2 (0x01) - target address
	# 3 (0x13) - function code (data type)
	# 4 (0x00) - data 1
	# 5 (0x00) - data 2
	# 6 (0x00) - data 3
	# 7 (0x??) - data 4
	# 8 (0x00) - checksum (sum 1-7)
	data_frame = [0x55, 0x01, 0x13, 0x00, 0x00, 0x00]
	global command_base = bytearray(data_frame)
	global command_base_crc = calc_crc(command_base)
	global answer_length = 8
	global answer_head = 0x22
	global answer_address = 0x01
	global answer_data_type = 0x00

def init():
	port = len(sys.argv) > 1 and sys.argv[1] or "/dev/ttyUSB0"
	global ser = serial.Serial(port, timeout = 2)
	init_protocol()
	global state = 0x00
	global stdscr = curses.initscr()
	curses.noecho()
	curses.cbreak()
	stdscr.keypad(True)
	# clear screen
	stdscr.clear()

def gen_command(state):
	command = bytearray(command_base)
	command.append(state)
	# checksum
	command.append(calc_crc(command))
	return command

def parse_answer(bytes):
	if (bytes[0] == answer_head and bytes[1] == answer_address and
			bytes[2] == answer_data_type):
		if state != bytes[6]:
			state = bytes[6]
			print("Update state", state)
		else:
			print("Check state [OK]")
	else:
		print("check state [FAIL]", bytes)
	
def change_state(relay_state):
	ser.write(gen_command(relay_state))
	answer = ser.read(answer_length)
	parse_answer(answer)

def loop():
	number = 1
	while True:
		c = stdscr.getkey()
		if c in channels:
			number = int(c)
		elif c == curses.KEY_DOWN:
			change_state(enable_relay(number, state))
		elif c == curses.KEY_UP:
			change_state(disable_relay(number, state))
		elif c == 'q':
			break

def finish():
	curses.nocbreak()
	stdscr.keypad(False)
	curses.echo()
	curses.endwin()
	ser.close()

init()
wrapper(loop())
finish()