Как восстановить из serialException с помощью pySerial

У меня есть приложение, которое считывает и передает данные на устройство, подключенное через USB. Я использую pySerial для облегчения этого сообщения. Все работает нормально до тех пор, пока USB-кабель не будет отсоединен от ПК и не будет выбрано исключение. Как только кабель снова вставлен, я не могу восстановить и снова подключиться к моему устройству. Единственный способ восстановить - закрыть приложение и отключить и снова подключить кабель. Любая помощь в понимании того, что происходит, будет очень оценена.

Это базовый тестовый код, который я использую, чтобы помочь мне понять этот процесс.

# Class used to communicate with USB Dongle

import serial
import time
import sys

class LPort:
  def __init__(self, port=0):
    "initialize the LPort class"
    self.error = ""
    self.traffic = ""
    self.dest = None
    if port == None:
        self.simulation = True
    else:
        self.simulation = False
        self.port = port # serial port we should use
    self.reset()
    self.time = time.time()

def reInit(self):
    self.close()

def reset(self):
    "flush port, reset the LPort, initialize LPort"
    if self.simulation:
        r = "LPort simulator"
    else:
        self.port.flushInput()
        self.port.flushOutput()           
        self.fail = False
        self.command("/H1")
        self.dest = None
        r = "reset"
    self.error = ""
    self.traffic = ""
    return r  

def status(self):
    "return accumulated status info, reset collection"
    s = self.error
    self.error = ""
    return s 

def data(self):
    "return accumulated traffic data, reset collection"
    s = self.traffic
    self.traffic = ""
    return s   

def set_dest(self, addr):
    "set the destination address (if necessary)"
    if addr != self.dest:
        self.dest = addr
        self.command("/O")
        r = self.command("/D%02X" % addr)
        if r != "*":
            self.dest = None
            self.error += r
        else:
            r = True
    return r 

def checksum(self, bytes):
    "calculate the CRC-8 checksum for the given packet"
    crc_table = [
            # this table is taken from the CP rectifier code
            0x00,0x07,0x0E,0x09,0x1C,0x1B,0x12,0x15,0x38,0x3F,
            0x36,0x31,0x24,0x23,0x2A,0x2D,0x70,0x77,0x7E,0x79,
            0x6C,0x6B,0x62,0x65,0x48,0x4F,0x46,0x41,0x54,0x53,
            0x5A,0x5D,0xE0,0xE7,0xEE,0xE9,0xFC,0xFB,0xF2,0xF5,
            0xD8,0xDF,0xD6,0xD1,0xC4,0xC3,0xCA,0xCD,0x90,0x97,
            0x9E,0x99,0x8C,0x8B,0x82,0x85,0xA8,0xAF,0xA6,0xA1,
            0xB4,0xB3,0xBA,0xBD,0xC7,0xC0,0xC9,0xCE,0xDB,0xDC,
            0xD5,0xD2,0xFF,0xF8,0xF1,0xF6,0xE3,0xE4,0xED,0xEA,
            0xB7,0xB0,0xB9,0xBE,0xAB,0xAC,0xA5,0xA2,0x8F,0x88,
            0x81,0x86,0x93,0x94,0x9D,0x9A,0x27,0x20,0x29,0x2E,
            0x3B,0x3C,0x35,0x32,0x1F,0x18,0x11,0x16,0x03,0x04,
            0x0D,0x0A,0x57,0x50,0x59,0x5E,0x4B,0x4C,0x45,0x42,
            0x6F,0x68,0x61,0x66,0x73,0x74,0x7D,0x7A,0x89,0x8E,
            0x87,0x80,0x95,0x92,0x9B,0x9C,0xB1,0xB6,0xBF,0xB8,
            0xAD,0xAA,0xA3,0xA4,0xF9,0xFE,0xF7,0xF0,0xE5,0xE2,
            0xEB,0xEC,0xC1,0xC6,0xCF,0xC8,0xDD,0xDA,0xD3,0xD4,
            0x69,0x6E,0x67,0x60,0x75,0x72,0x7B,0x7C,0x51,0x56,
            0x5F,0x58,0x4D,0x4A,0x43,0x44,0x19,0x1E,0x17,0x10,
            0x05,0x02,0x0B,0x0C,0x21,0x26,0x2F,0x28,0x3D,0x3A,
            0x33,0x34,0x4E,0x49,0x40,0x47,0x52,0x55,0x5C,0x5B,
            0x76,0x71,0x78,0x7F,0x6A,0x6D,0x64,0x63,0x3E,0x39,
            0x30,0x37,0x22,0x25,0x2C,0x2B,0x06,0x01,0x08,0x0F,
            0x1A,0x1D,0x14,0x13,0xAE,0xA9,0xA0,0xA7,0xB2,0xB5,
            0xBC,0xBB,0x96,0x91,0x98,0x9F,0x8A,0x8D,0x84,0x83,
            0xDE,0xD9,0xD0,0xD7,0xC2,0xC5,0xCC,0xCB,0xE6,0xE1,
            0xE8,0xEF,0xFA,0xFD,0xF4,0xF3]
    for i in range(len(bytes)):
        b = int(bytes[i])
        if i == 0: chksum = crc_table[b]
        else: chksum = crc_table[chksum ^ b]
    return chksum  

def command(self, cmd):
    "transmit distinct commands to unit, and accept response"
    if self.simulation:
        r = "*"
    else:
        try:
            self.port.write(cmd + chr(13))
        except serial.serialutil.SerialTimeoutException:
            r = "/TO"
            return r              
        except:
            print "Unexpected error:", sys.exc_info()[0]
            r = "/Unknown"
            return r
        r = ""
        eol = False
        while True:
            c = self.port.read(1)
            if not c:
                r = "/FAIL " + r + " " + cmd
                self.error = r
                break
            else:
                r += c
                ordc = ord(c)
                if ordc == 13 or ordc == 42:
                    break           
    return r

def checkRawDataForErrors(self, raw, errors = []):

    errorCodes = {'/SNA':'Slave Not Acknowledging',
                    '/I81':'Busy, Command Ignored',
                    '/I88':'Connection Not Open',
                    '/I89':'Invalid Command Argument',
                    '/I8A':'Transmit Not Active',
                    '/I8F':'Invalid Command',
                    '/I90':'Buffer Overflow',
                    '/DAT':'Data Error',
                    '/BADPEC':'Bad PEC Value',
                    '/NO_MRC':'No Master Read Complete Signal',
                    '/FAIL':'General Failure',
                    '/LEN':'Data Length Error'}

    for ekey, eval in errorCodes.items():
        if ekey in raw:
            errors.append(eval)

    return errors        
# self-testing module
if __name__ == "__main__":

  com = serial.Serial(port=4, baudrate=115200, timeout=1, xonxoff=0)

  if com:
    port = LPort(com)
    print port
    time.sleep(5)

    port = LPort(com)

    print "/V =", port.command("/V")
    print "/V", port.data(), port.status()
    print "/O =", port.command("/O")
    print "/O", port.data(), port.status()
    print "/A =", port.command("/A")
    print "/A", port.data(), port.status()
    print "/L =", port.command("/L")
    print "/L", port.data(), port.status()
    com.close()
else:
    print "cannot open com port"

UPDATE: Ниже приведен код вокруг файла creatfile() в serialwin32.py, который возвращает следующее сообщение: serial.serialutil.SerialException: не удалось открыть порт COM5: [Ошибка 2] Система не может найти указанный файл.

    self.hComPort = win32.CreateFile(port,
           win32.GENERIC_READ | win32.GENERIC_WRITE,
           0, # exclusive access
           None, # no security
           win32.OPEN_EXISTING,
           win32.FILE_ATTRIBUTE_NORMAL | win32.FILE_FLAG_OVERLAPPED,
           0)
    if self.hComPort == win32.INVALID_HANDLE_VALUE:
        self.hComPort = None    # 'cause __del__ is called anyway
        raise SerialException("could not open port %s: %s" % (self.portstr,  ctypes.WinError())) 

Ответы

def try_to_open_new_port(self):
    ret = False
    test = serial.Serial(baudrate=9600, timeout=0, writeTimeout=0)
    test.port = self.current_port_name
    try:
        test.open()
        if test.isOpen():
            test.close()
            ret = True
    except serial.serialutil.SerialException:
        pass
    return ret