python - 连接2个Modbus从站pymodbus时出错

我正在研究pymodbus。
尝试从多个单元（多个从机）读取数据时，它会提供数据，但当其中一个从机没有响应或关闭时，其他从机在一段时间后也会显示错误。
请帮忙。
谢谢你

from pymodbus.client.sync import ModbusSerialClient as ModbusClient
from pymodbus.constants import Endian
from pymodbus.payload import BinaryPayloadDecoder
from pymodbus.exceptions import ModbusIOException
from pymodbus.exceptions import ConnectionException

def length(x):
    client = ModbusClient(method='rtu', port='/dev/ttyUSB0', timeout=2, stopbits = 1, bytesize = 8,  parity='N', baudrate = 9600)
    client.connect()
    rr = client.read_holding_registers(address=1, count=4, unit=x);
    decoder = BinaryPayloadDecoder.fromRegisters(rr.registers, Endian.Big, wordorder=Endian.Big);
    a=str(decoder.decode_32bit_float());
    c = int (float(a))
    client.close()
    print("length",c)
    client = ModbusClient(method='rtu', port='/dev/ttyUSB0', timeout=2, stopbits = 1, bytesize = 8,  parity='N', baudrate = 9600)
    client.connect()
    rr = client.read_holding_registers(address=7, count=4, unit=x);
    decoder = BinaryPayloadDecoder.fromRegisters(rr.registers, Endian.Big, wordorder=Endian.Big);
    b=str(decoder.decode_32bit_float());
    d = int (float(b))
    client.close()
    print("speed",d)
    print(x)
    return c,d

最佳答案

我用pymodbus中的.isError()方法改进了您的代码，如下所示：

from pymodbus.client.sync import ModbusSerialClient as ModbusClient
from pymodbus.constants import Endian
from pymodbus.payload import BinaryPayloadDecoder

def error_checker(instance):
    if not instance.isError():
        '''.isError() implemented in pymodbus 1.4.0 and above.'''
        decoder = BinaryPayloadDecoder.fromRegisters(
            instance.registers, byteorder=Endian.Big, wordorder=Endian.Big
        )
        return decoder.decode_32bit_float()
    else:
        # Error handling.
        return None

def length(x):
    client = ModbusClient(
        method='rtu',
        port='/dev/ttyUSB0',
        timeout=2, stopbits=1, bytesize=8, parity='N', baudrate=9600
    )
    try:
        client.connect()
        rr = client.read_holding_registers(address=1, count=4, unit=x)
        c = error_checker(rr)
        print("length: ", c)
        rr = client.read_holding_registers(address=7, count=4, unit=x)
        d = error_checker(rr)
        print("speed: ", d)
        return c, d
    except Exception as exc:
        print(exc)
    finally:
        client.close()