PyModbus服务器返回错误寄存器值问题排查求助

问题现象 #

• 服务器在保持寄存器中存储值[16689, 39322]
• 客户端读取到的却是[39322, 0]
• 转换后的浮点数为无效值：-1.5923226791645783e-23

环境 #

• Python 3.12.12
• PyModbus 3.11.3

代码实现 #

import asyncio 
import json 
from pymodbus.server import StartAsyncTcpServer
from pymodbus.datastore import ModbusDeviceContext, ModbusServerContext, ModbusSequentialDataBlock
from pymodbus import ModbusDeviceIdentification, FramerType
from pymodbus.client.mixin import ModbusClientMixin
from pymodbus.client import ModbusTcpClient

with open('teplomonitor_data.json', 'r') as file:
    data = json.load(file)

temperature = float(data['parameters']['outdoor_temperature'])

registers = ModbusClientMixin.convert_to_registers(
    value=temperature,
    data_type=ModbusClientMixin.DATATYPE.FLOAT32, 
    word_order='big'
)

holding_registers = ModbusSequentialDataBlock(0, [0] * 100)

holding_registers.setValues(address=0, values=registers)
print(holding_registers.getValues(address=0, count=2))

device_context = ModbusDeviceContext(
    di=holding_registers, 
    co=holding_registers, 
    hr=holding_registers, 
    ir=holding_registers 
)

server_context = ModbusServerContext(
    devices=device_context, 
    single=True
    )

identity = ModbusDeviceIdentification()
identity.VendorName = 'PyModbus Server'
identity.ProductCode = 'PM'
identity.VendorUrl = 'http://github.com/pymodbus-dev/pymodbus/'
identity.ProductName = 'PyModbus TCP Server'
identity.ModelName = 'PyModbus'
identity.MajorMinorRevision = '2.0'

host = '127.0.0.1'
port = 5020

async def run_server():
    print(f"Start Modbus TCP server on {host}:{port}")
    print("Press Ctrl+C to stop")

    try:
        await StartAsyncTcpServer(
        context=server_context,  
        identity=identity,  
        address=(host, port),  
        framer=FramerType.SOCKET,  
    )

    except asyncio.CancelledError:
        print('Server is stopped')
    except Exception as e:
        print(f"Server error: {e}")

def test_client():
    print("Client testing")
    try:
        client = ModbusTcpClient(host='127.0.0.1', port=5020)
        client.connect()
        response = client.read_holding_registers(address=0, count=2)
        
        if not response.isError():
            print("Registers values:", response.registers)
            value = ModbusClientMixin.convert_from_registers(
                response.registers,
                data_type=ModbusClientMixin.DATATYPE.FLOAT32,
                word_order='big'
            )
            print(f"Temperature processed value: {value}")
        else:
            print("Registers reading error:", response)
            
        client.close()
    except Exception as e:
        print(f"Client error: {e}")

async def main():
    server_task = asyncio.create_task(run_server())

    await asyncio.sleep(2)

    test_client()
    try:
        await server_task
    except KeyboardInterrupt:
        print("\nServer stopped by user")

if __name__ == '__main__':
    asyncio.run(main())

输出结果 #

[16689, 39322]
Start Modbus TCP server on 127.0.0.1:5020
Press Ctrl+C to stop
Client testing
Registers values: [39322, 0]
Temperature processed value: -1.5923226791645783e-23

期望结果 #

客户端执行response = client.read_holding_registers(address=0, count=2)时，期望得到[16689, 39322]。

内容的提问来源于stack exchange，提问作者Inal Kochesokov