1

我在使用 pymodbus 的树莓派 3B 上出现连接错误。使用 MAX14854G 作为 RS-485 收发器设计了一块电路板，连接到 RPI3 的 UART 引脚（8 和 10）。它通过 T1、T2 和 T4 (GND) 引脚连接到 m-system 电能表 (53U-1211-AD4/H)。

附加信息：我通过使用此过程使用 UART 的全部功能：链接

这是我的代码：

In [3]: import pymodbus

In [4]: import serial.rs485

In [5]: from pymodbus.client.sync import ModbusSerialClient as ModbusClient

In [6]: from pymodbus.register_read_message import ReadInputRegistersResponse

In [7]: msys = ModbusClient(method='rtu',port='/dev/ttyAMA0',stopbits=1,bytesize=8,parity='N',baudrate=9600,timeout=5)

In [8]: msys.connect()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-8-31c23cb3ed21> in <module>()
----> 1 msys.connect()

/usr/local/lib/python3.5/dist-packages/pymodbus/client/sync.py in connect(self)
474             self.close()
475         if self.method == "rtu":
--> 476             self.socket.interCharTimeout = self.inter_char_timeout
477             self.last_frame_end = None
478         return self.socket is not None

更新：

遵循@BenyaminJafari 的建议并更改了 root 权限：

sudo chmod 777 /dev/ttyAMA0

我终于可以按照以下代码进行连接，但导致了不同的错误：

In [39]: msys.connect()
Out[39]: True

In [40]: valueHoldingRegisters = msys.read_holding_registers(1,1,unit=1)

In [41]: valueHoldingRegisters = msys.read_holding_registers(1,1,unit=1)

In [42]: valueHoldingRegisters.isError()
Out[42]: True

In [43]: print(valueHoldingRegisters)
Modbus Error: [Input/Output] Modbus Error: [Invalid Message] Incomplete message received, expected at least 2 bytes (0 received)

错误日志：

DEBUG:pymodbus.transaction:Current transaction state - IDLE
DEBUG:pymodbus.transaction:Running transaction 1
DEBUG:pymodbus.transaction:SEND: 0x1 0x3 0x0 0x1 0x0 0x1 0xd5 0xca
DEBUG:pymodbus.client.sync:New Transaction state 'SENDING'
DEBUG:pymodbus.transaction:Changing transaction state from 'SENDING' to 'WAITING FOR REPLY'
DEBUG:pymodbus.transaction:Transaction failed. (Modbus Error: [Invalid Message] Incomplete message received, expected at least 2 bytes (0 received)) 
DEBUG:pymodbus.framer.rtu_framer:Frame - [b''] not ready
DEBUG:pymodbus.transaction:Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'
Unhandled error

更新（添加了一些新行）：

In [1]: import pymodbus

In [2]: import serial

In [3]: from pymodbus.pdu import ModbusRequest

In [4]: from pymodbus.client.sync import ModbusSerialClient as ModbusClient

In [5]: from pymodbus.transaction import ModbusRtuFramer

In [6]: from pymodbus.register_read_message import ReadInputRegistersResponse

In [7]: import logging

In [8]: logging.basicConfig()

In [9]: log = logging.getLogger()

In [10]: log.setLevel(logging.DEBUG)

In [11]: msys = ModbusClient(method='rtu',port='/dev/ttyAMA0',stopbits=1,bytesize=8,parity='N',baudrate=9600,timeout=2)

In [12]: connection = msys.connect()

In [13]: print(connection)
True

In [14]: HR1 = msys.read_holding_registers(0,1,unit=1)
DEBUG:pymodbus.transaction:Current transaction state - IDLE
DEBUG:pymodbus.transaction:Running transaction 1
DEBUG:pymodbus.transaction:SEND: 0x1 0x3 0x0 0x0 0x0 0x1 0x84 0xa
DEBUG:pymodbus.client.sync:New Transaction state 'SENDING'
DEBUG:pymodbus.transaction:Changing transaction state from 'SENDING' to 'WAITING FOR REPLY'
DEBUG:pymodbus.transaction:Transaction failed. (Modbus Error: [Invalid Message] Incomplete message received, expected at least 2 bytes (0 received)) 
DEBUG:pymodbus.framer.rtu_framer:Frame - [b''] not ready
DEBUG:pymodbus.transaction:Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'

In [15]: print(HR1)
Modbus Error: [Input/Output] Modbus Error: [Invalid Message] Incomplete message received, expected at least 2 bytes (0 received)

In [25]: HR2= msys.read_holding_registers(1,1,unit=1)
DEBUG:pymodbus.transaction:Current transaction state - TRANSACTION_COMPLETE
DEBUG:pymodbus.transaction:Running transaction 2
DEBUG:pymodbus.transaction:SEND: 0x1 0x3 0x0 0x1 0x0 0x1 0xd5 0xca
DEBUG:pymodbus.framer.rtu_framer:Changing state to IDLE - Last Frame End - None, Current Time stamp - 1478195437.918486
DEBUG:pymodbus.client.sync:New Transaction state 'SENDING'
DEBUG:pymodbus.transaction:Changing transaction state from 'SENDING' to 'WAITING FOR REPLY'
DEBUG:pymodbus.transaction:Incomplete message received, Expected 7 bytes Recieved 0 bytes !!!!
DEBUG:pymodbus.transaction:Changing transaction state from 'WAITING FOR REPLY' to 'PROCESSING REPLY'
DEBUG:pymodbus.transaction:RECV: 
DEBUG:pymodbus.framer.rtu_framer:Frame - [b''] not ready
DEBUG:pymodbus.transaction:Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'

In [26]: print(HR2)
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response

In [27]: HR3 = msys.read_holding_registers(2,1,unit=1)
DEBUG:pymodbus.transaction:Current transaction state - TRANSACTION_COMPLETE
DEBUG:pymodbus.transaction:Running transaction 3
DEBUG:pymodbus.transaction:SEND: 0x1 0x3 0x0 0x2 0x0 0x1 0x25 0xca
DEBUG:pymodbus.framer.rtu_framer:Changing state to IDLE - Last Frame End - 1478195439.927521, Current Time stamp - 1478195492.844382
DEBUG:pymodbus.client.sync:New Transaction state 'SENDING'
DEBUG:pymodbus.transaction:Changing transaction state from 'SENDING' to 'WAITING FOR REPLY'
DEBUG:pymodbus.transaction:Incomplete message received, Expected 7 bytes Recieved 0 bytes !!!!
DEBUG:pymodbus.transaction:Changing transaction state from 'WAITING FOR REPLY' to 'PROCESSING REPLY'
DEBUG:pymodbus.transaction:RECV: 
DEBUG:pymodbus.framer.rtu_framer:Frame - [b''] not ready
DEBUG:pymodbus.transaction:Changing transaction state from 'PROCESSING REPLY' to 'TRANSACTION_COMPLETE'

In [28]: print(HR3)
Modbus Error: [Input/Output] No Response received from the remote unit/Unable to decode response

有人可以帮忙并建议我哪里出错了吗？

4

1 回答 1

0

我设置了 Modbus 从日志以获取更多信息：

import logging
from pymodbus.client.sync import ModbusSerialClient as ModbusClient

logging.basicConfig()
log = logging.getLogger()
log.setLevel(logging.DEBUG)

msys = ModbusClient(
    method='rtu', port='/dev/ttyAMA0',
    stopbits=1, bytesize=8, parity='N',
    baudrate=9600, timeout=5
)

if msys.connect():
    try:
        valueHoldingRegisters = msys.read_holding_registers(1, 1, unit=1)

        if not valueHoldingRegisters.isError():
            print(valueHoldingRegisters.registers)

        else:
            raise ValueError(valueHoldingRegisters)

    except Exception as exc:
        print(exc)

else:
    print('Connection error')

msys.close()

[注意]：

确保您的端口应具有 root 权限，使用：

sudo chmod 777 /dev/ttyAMA0
于 2018-12-06T09:44:13.480 回答