Question

我已经实现了一个pymodbus TcpServer，它根据一些UART通信更新了它的上下文。我使用LoopingCall进行UART通信并更新modbus上下文。在LoopingCall期间，我发送了一些UART消息并等待适当的答案。您可以看到缩短和简化的代码（请注意，代码不会以这种方式运行，但我希望您能看到我的工作方式）。

#!/usr/bin/env python
'''
Pymodbus Server With Updating Thread
--------------------------------------------------------------------------

This is an example of having a background thread updating the
context while the server is operating. This can also be done with
a python thread::

    from threading import Thread

    thread = Thread(target=updating_writer, args=(context,))
    thread.start()
'''
#---------------------------------------------------------------------------# 
# import the modbus libraries we need
#---------------------------------------------------------------------------# 
from pymodbus.server.async import StartTcpServer
from pymodbus.device import ModbusDeviceIdentification
from pymodbus.datastore import ModbusSequentialDataBlock
from pymodbus.datastore import ModbusSlaveContext, ModbusServerContext
from pymodbus.transaction import ModbusRtuFramer, ModbusAsciiFramer

#---------------------------------------------------------------------------# 
# import the twisted libraries we need
#---------------------------------------------------------------------------# 
from twisted.internet.task import LoopingCall

#---------------------------------------------------------------------------# 
# define your callback process
#---------------------------------------------------------------------------# 
def updating_writer(a):
    context  = a[0]
    register = 3
    slave_id = 0x00
    address  = 0x10
    _ser_ = serial.Serial(
            #port = '/dev/ttyUSB0',
            port = dev,
            baudrate=115200,
            parity=serial.PARITY_NONE,
            stopbits=serial.STOPBITS_ONE,
            bytesize=serial.EIGHTBITS
        )
    _ser_.open()
    _ser_.write("Example")
    inbuff = []
    values = []
    @timeout(0.1)
    while True:
        inbuff.append(_ser_.read(1))
        # come kind of checksum calculation, to check if message is complete
        if checkmessage(inbuff):
            values = ord(inbuff[0])
            break
    context[slave_id].setValues(register, address, values)

#---------------------------------------------------------------------------# 
# initialize your data store
#---------------------------------------------------------------------------# 
store = ModbusSlaveContext(
    di = ModbusSequentialDataBlock(0, [17]*100),
    co = ModbusSequentialDataBlock(0, [17]*100),
    hr = ModbusSequentialDataBlock(0, [17]*100),
    ir = ModbusSequentialDataBlock(0, [17]*100))
context = ModbusServerContext(slaves=store, single=True)

#---------------------------------------------------------------------------# 
# initialize the server information
#---------------------------------------------------------------------------# 
identity = ModbusDeviceIdentification()
identity.VendorName  = 'pymodbus'
identity.ProductCode = 'PM'
identity.VendorUrl   = 'http://github.com/bashwork/pymodbus/'
identity.ProductName = 'pymodbus Server'
identity.ModelName   = 'pymodbus Server'
identity.MajorMinorRevision = '1.0'

#---------------------------------------------------------------------------# 
# run the server you want
#---------------------------------------------------------------------------# 
time = 5 # 5 seconds delay
loop = LoopingCall(f=updating_writer, a=(context,))
loop.start(time, now=False) # initially delay by time
StartTcpServer(context, identity=identity, address=("localhost", 5020))

只是为了完整性，这里是超时功能（我在Stackoverflow上找到了类似的例子）。

from functools import wraps
import errno
import os
import signal

class TimeoutError(Exception):
    pass

def timeout(seconds=10, error_message=os.strerror(errno.ETIME)):
    def decorator(func):
        def _handle_timeout(signum, frame):
            raise TimeoutError(error_message)

        def wrapper(*args, **kwargs):
            signal.signal(signal.SIGALRM, _handle_timeout)
            #signal.alarm(seconds)
            signal.setitimer(signal.ITIMER_REAL,seconds)
            try:
                result = func(*args, **kwargs)
            finally:
                #signal.alarm(0)
                signal.setitimer(signal.ITIMER_REAL,0)
            return result

        return wraps(func)(wrapper)

    return decorator

对我来说，似乎pymodbus TcpServer在LoopingCall操作（updating_writer()）期间冻结。

这个LoopingCall是否在自己的线程中运行，还是阻止pymodbus TcpServer操作？我怎样才能实现这一点，以便TcpServer不会冻结？

顺便说一句：这段代码在raspberry jessie和python-2.7上覆盖着树莓。

编辑：我想我需要修改我的问题，因为根据Twisted LoopingCall with blocking function LoopingCall似乎在主线程中运行并阻止其他操作。

如何修改我的代码，以便在更新任务期间不会阻止pymodbus TcpServer？

在LoopingCall期间继续pymodbus TcpServer操作

0 个答案: