pymodbus:从 Modbus 设备读取字符串和多种类型的数据

pymodbus: Issue reading String & multiple type of data from Modbus device

我正在尝试从 Modbus TCP 设备读取 String (Usecase-1) & multiple type of data in one request (Usecase-2) 数据,但是失败了正确解码。

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:

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 客户端应将字符串解码为 abcdefghij,但它却将其解码为 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 byteorderwordorder 的所有组合,但是,它对任何情况都不起作用。

请帮助我理解为什么数据会这样解码?我在编码或解码此数据时是否错过了要添加的内容?

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,但未能按预期工作。

如有任何帮助,我们将不胜感激。

Tl;博士。在 ModbusSlaveContext.

中使用 zero_mode=True

如果您想将客户端中的寄存器 [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。引用自 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,您可以将 ModbusSequentialDataBlock 的起始地址设置为 1 或使用 zero_mode=True.

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