我有读取并通过USB连接的装置发送数据的应用程序。 我使用pySerial实现这种通信。 直到USB电缆从电脑拔下，并抛出一个异常，一切工作正常。 一旦电缆被后面插上，我似乎无法恢复和重新连接到我的设备。 对我来说，恢复的唯一方法是关闭该应用程序并拔出并重新插入电缆。 在了解任何帮助是怎么回事，将不胜感激。
这是我对期运用帮助我理解这个过程基本的测试代码。
# 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：以下是在周围的serialwin32.py creatfile（），它返回下列消息中的代码：serial.serialutil.SerialException：无法打开端口COM5：[错误2]系统无法找到指定的文件。
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()))
