如何将树莓pi与PLC通信？我不断出错，任何帮助都将不胜感激

Question

我对覆盆子pi和PLC的世界还很陌生，好像我知道的很少一样。但是，我正在尝试在raspberry pi和PLC之间进行USB通信。 我使用的PLC是VersaMax（IC200NDR010-FJ），它只有一个ej45端口，所以我使用USB到ej45转换器进行通信。下面是我在网上找到的代码，看起来非常简单。但是，当我尝试运行该程序时，我得到了“ValueError:不是有效的奇偶校验：'0.”这是我的尝试#1

pi@raspberrypi:~ $ ipython
SudoPython 2.7.16 (default, Apr  6 2019, 01:42:57) 
Type "copyright", "credits" or "license" for more information.

IPython 5.9.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: from pymodbus.client.sync import ModbusSerialClient

In [2]: client = ModbusSerialClient(method='rtu' ,port=' /dev/ttyUSB0' ,baudrate
   ...: =9600, parity='0')

In [3]: client.read_coils(2048,1,unit=1).bits
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-3-ecf7c3f6dc42> in <module>()
----> 1 client.read_coils(2048,1,unit=1).bits

/home/pi/.local/lib/python2.7/site-packages/pymodbus/client/common.pyc in read_coils(self, address, count, **kwargs)
     46         '''
     47         request = ReadCoilsRequest(address, count, **kwargs)
---> 48         return self.execute(request)
     49 
     50     def read_discrete_inputs(self, address, count=1, **kwargs):

/home/pi/.local/lib/python2.7/site-packages/pymodbus/client/sync.pyc in execute(self, request)
    104         :returns: The result of the request execution
    105         """
--> 106         if not self.connect():
    107             raise ConnectionException("Failed to connect[%s]" % (self.__str__()))
    108         return self.transaction.execute(request)

/home/pi/.local/lib/python2.7/site-packages/pymodbus/client/sync.pyc in connect(self)
    595                                         stopbits=self.stopbits,
    596                                         baudrate=self.baudrate,
--> 597                                         parity=self.parity)
    598             if self.method == "rtu":
    599                 if self._strict:

/usr/lib/python2.7/dist-packages/serial/serialutil.pyc in __init__(self, port, baudrate, bytesize, parity, stopbits, timeout, xonxoff, rtscts, write_timeout, dsrdtr, inter_byte_timeout, exclusive, **kwargs)
    219         self.baudrate = baudrate
    220         self.bytesize = bytesize
--> 221         self.parity = parity
    222         self.stopbits = stopbits
    223         self.timeout = timeout

/usr/lib/python2.7/dist-packages/serial/serialutil.pyc in parity(self, parity)
    330         """Change parity setting."""
    331         if parity not in self.PARITIES:
--> 332             raise ValueError("Not a valid parity: {!r}".format(parity))
    333         self._parity = parity
    334         if self.is_open:

ValueError: Not a valid parity: '0'

In [4]: 

尝试#2 我尝试一次提交一个命令，希望能够修复无效的奇偶校验，但最终收到另一个错误：“TypeError:必须使用ModbusSerialClient实例作为第一个参数调用unbound method read_coils（）（改为使用int instance）。”

pi@raspberrypi:~ $ ipython 
Python 2.7.16 (default, Apr  6 2019, 01:42:57) 
Type "copyright", "credits" or "license" for more information.

IPython 5.9.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

In [1]: from pymodbus.client.sync import ModbusSerialClient

In [2]: client = ModbusSerialClient

In [3]: method='rtu'

In [4]: port=' /dev/ttyUSB0'

In [5]: baudrate=9600

In [6]: parity='0'

In [7]: client.read_coils(2048,1,unit=1).bits
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-ecf7c3f6dc42> in <module>()
----> 1 client.read_coils(2048,1,unit=1).bits

TypeError: unbound method read_coils() must be called with ModbusSerialClient instance as first argument (got int instance instead)

In [8]: 

对此任务的任何指导都将不胜感激！我试图在陡峭的弯道上学习这一点

谢谢大家!