import serial
porta_seriale = str(input('A quale porta seriale devo connettermi? '))
try:
    ser = serial.Serial(porta_seriale, 9600)
except:
    print('non riesco a connettermi')
    exit()

print('OK, sono connesso')
while True:
    if ser.readline() == b'C\r\n':
        print('=>')

    elif ser.readline() == b'D\r\n':
        print('<=')

    elif ser.readline() == b'A\r\n':
        print('↑')

    elif ser.readline() == b'B\r\n':
        print('↓')

    elif ser.readline() == b'OK\r\n':
        print('OK')