import serial
import random
from time import sleep

START_BYTE = b'\xA5'


def calculate_crc(message):
    return sum(message[0:-1]) % 256


def build_message(message):
    message_out = bytearray(message)
    message_out[-1] = calculate_crc(message_out)
    return message_out


serial_port = serial.Serial(port='/dev/ttyUSB1', baudrate=115200)

# Building response message
response_message = build_message(START_BYTE + b'\x00\x03' + b'\x01' + b'\x00' + b'\x00')

# Building Async response message
async_message = build_message(START_BYTE + b'\x00\x02' + b'\x02' + b'\x01\x02' + b'\x00')

# Building Sync response message
sync_message = build_message(START_BYTE + b'\x00\x05' + b'\x02' + b'\x05\x06' + b'\x00')

counter = 0

print("")
print("o -> response")
print(". -> Sync")
print("x -> Async")
print("")


while True:

    bytes_in_serial_port = serial_port.in_waiting;

    if bytes_in_serial_port != 0:
        # This is what we received
        serial_port.read(bytes_in_serial_port)

        # Answer immediately
        serial_port.write(response_message)

        # Show on the screen
        print("o", end='', flush=True)


    sleep(0.05)

    counter += 1

    if counter == 20:
        counter = 0

        # Send Sync Values
        serial_port.write(sync_message)

        print(".", end='', flush=True)

    if random.randint(1, 100) == 69:
        # Send Async message
        serial_port.write(async_message)

        print("x", end='', flush=True)