pymodbus：从Modbus设备发出读取字符串和多种类型的数据

Question

我试图从Modbus TCP设备读取String（Usecase-1）&；multiple type of data in one request（Usecase-2）数据，但未能正确解码。在

系统配置：

Python 3.6.5
Pymodbus: 2.1.0
Platform: Windows 10 64-bit

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：

^{pr2}$

输出用例1:

Result :  ReadRegisterResponse (5)
name     cdefghijab

Modbus客户端应该将字符串解码为abcdefghij，但它将其解码为cdefghijab。在

输出用例2:

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

看看上面读取多个寄存器的输出，输出值与BinaryPayloadBuilder的输入值不匹配。在

我已经尝试过byteorder&；wordorder的所有组合，但它对任何情况都不起作用。在

请帮助我理解为什么数据会这样解码？在编码或解码这些数据时，我是否遗漏了一些要添加的内容？在

仅供参考：此解决方案与Pymodbus 1.5.1版本配合良好。最近我升级了版本，但未能如期工作。在

任何帮助都将不胜感激。在

Answer 1

dr.在ModbusSlaveContext中使用zero_mode=True。在

如果要将客户机中的寄存器[0..n]映射到服务器中的[0..n]。默认情况下，pymodbus服务器将地址[0..n]的寄存器读取映射到其内部存储中的寄存器[1..n]。这是为了遵守modbus规范。引用pymodbus源代码。在

#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)::

所以在您的例子中，您可以将ModbusSequentialDataBlock的起始地址设置为1，或者使用zero_mode=True初始化{}。在

    hrBlock = ModbusSequentialDataBlock(1, hrBuilder.to_registers() * 100)
    # Or
    store = ModbusSlaveContext(hr=hrBlock, ir=hrBlock, di=hrBlock, co=hrBlock, zero_mode=True)