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()))
