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我正在尝试从Modbus TCPString设备读取(Usecase-1) & multiple type of data in one request(Usecase-2) 数据，但它未能正确解码。

系统配置：

Python 3.6.5
Pymodbus：2.1.0
平台：Windows 10 64 位

Modbus TCP 服务器：

import logging

from pymodbus.constants import Endian
from pymodbus.datastore import ModbusSequentialDataBlock
from pymodbus.datastore import ModbusSlaveContext, ModbusServerContext
from pymodbus.device import ModbusDeviceIdentification
from pymodbus.payload import BinaryPayloadBuilder
from pymodbus.server.sync import StartTcpServer

class ModbusTCPServer(object):
    # initialize your data store:
    hrBuilder = BinaryPayloadBuilder(byteorder=Endian.Big, wordorder=Endian.Big)
    # Usecase-1
    hrBuilder.add_string("abcdefghij")

    #Uncomment below three lines for usecase-2
    # hrBuilder.add_32bit_float(20.5) 
    # hrBuilder.add_32bit_int(45) 
    # hrBuilder.add_bits([1, 0, 0, 0, 0, 0, 0, 0])

    hrBlock = ModbusSequentialDataBlock(0, hrBuilder.to_registers() * 100)
    store = ModbusSlaveContext(hr=hrBlock, ir=hrBlock, di=hrBlock, co=hrBlock)
    slaves = {
        1: store,
    }
    context = ModbusServerContext(slaves=slaves, single=False)

    # initialize the server information    
    identity = ModbusDeviceIdentification()

    modbusDeviceAddress = "127.0.0.1"
    modbusDevicePort = 501
    # run the TCP server

    # TCP:
    print("Modbus TCP Server started.")
    StartTcpServer(context, identity=identity, address=(modbusDeviceAddress, modbusDevicePort))


if __name__ == "__main__":
    print("Reading application configurations...")
    ModbusTCPServer();

Modbus TCP 客户端：

from pymodbus.client.sync import ModbusTcpClient as ModbusClient
from pymodbus.payload import BinaryPayloadDecoder
from pymodbus.constants import Endian
from pymodbus.compat import iteritems

if __name__ == '__main__':
    client = ModbusClient('127.0.0.1', port=501)
    client.connect()
    result  = client.read_holding_registers(0, 5,  unit=1)
    print("Result : ",result)
    decoder = BinaryPayloadDecoder.fromRegisters(result.registers, byteorder=Endian.Big, wordorder=Endian.Big)
    # Usecase-1
    decoded = {
        'name': decoder.decode_string(10).decode(),
    }

    # Usecase-2
    # decoded = {
    #    'temp': decoder.decode_32bit_float(),
    #    'rpm': decoder.decode_32bit_int(),
    #    'status': decoder.decode_bits()
    #}

    for name, value in iteritems(decoded):
        print ("%s\t" % name, value)
    client.close()

输出用例 1：

Result :  ReadRegisterResponse (5)
name     cdefghijab

Modbus 客户端应该将字符串解码为abcdefghij但是，它正在将其解码为cdefghijab.

输出用例 2：

Result :  ReadRegisterResponse (5)
temp     0.0
rpm  2949376
status   [True, False, False, False, False, False, True, False]

查看上面读取多个寄存器的输出，输出值与输入给定的值不匹配BinaryPayloadBuilder。

我已经尝试了byteorder&wordorder的所有组合，但是它不适用于任何情况。

请帮助我理解为什么数据会这样解码？在对这些数据进行编码或解码时，我是否遗漏了一些要添加的内容？

仅供参考：此解决方案适用于Pymodbus 1.5.1版本。最近我升级了版本，但它未能按预期工作。

任何帮助，将不胜感激。

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1 回答 1

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Tl;博士。zero_mode=True中使用ModbusSlaveContext。

如果您想将[0..n]客户端中[0..n]的寄存器映射到服务器中。默认情况下，pymodbus 服务器将寄存器读取地址映射到其内部存储中的[0..n]寄存器。[1..n]这是为了遵守 modbus 规范。引用 pymodbus 源代码。

#The slave context can also be initialized in zero_mode which means that a
# request to address(0-7) will map to the address (0-7). The default is
# False which is based on section 4.4 of the specification, so address(0-7)
# will map to (1-8)::

因此，在您的情况下，您可以设置ModbusSequentialDataBlockto的起始地址1或ModbusSlaveContext使用zero_mode=True.

    hrBlock = ModbusSequentialDataBlock(1, hrBuilder.to_registers() * 100)
    # Or
    store = ModbusSlaveContext(hr=hrBlock, ir=hrBlock, di=hrBlock, co=hrBlock, zero_mode=True)
于 2019-02-16T06:57:37.660 回答