如何处理 while 1 循环中的值错误并使用定时器 class 进行调度

Question

我写了一个代码来读取 modbus 通信协议的寄存器。我也附上了下面的代码.. 我能够通过异常处理方法克服 i/o 错误，其中作为我得到的值错误，我无法抛出该错误并继续前进。基本上我正在做的是读取寄存器中的数据并将其发送到服务器。但我的要求是我必须每秒读取这些值，持续 24 小时。所以我需要构建一个健壮的系统来克服这些值错误并继续执行我创建的线程。读取寄存器的代码如下：

import minimalmodbus
import serial
from ctypes import *
import struct
import time

minimalmodbus.BAUDRATE = 9600
minimalmodbus.PARITY = serial.PARITY_NONE
minimalmodbus.BYTESIZE = 8
minimalmodbus.TIMEOUT=5
minimalmodbus.CLOSE_PORT_AFTER_EACH_CALL = True
energy_meter = serial.Serial("/dev/ttyUSB0", baudrate=9600,
                            parity=serial.PARITY_NONE,
                            stopbits=serial.STOPBITS_ONE, bytesize=serial.EIGHTBITS, timeout=5)
energy_meter = minimalmodbus.Instrument('/dev/ttyUSB0', 2, mode='rtu')
#energy_meter.debug = True


def convert_in_float(value1, value2):
    raw = struct.pack('>HH',value1,value2)
    ans = struct.unpack('>f', raw)[0]
    return ans

def sdm630():
    parameter_list1 = [ 0 ] * 0x12
    parameter_list2 = [ 0 ] * 3
    parameter_list3 = [ 0 ] * 6
    #print energy_meter
    error = 0
    try:
            index = 0
            read_values1  = energy_meter.read_registers( 0 , 0x24, 4)
            for i in range ( 0, 0x24, 2):
                    parameter_list1[index] = convert_in_float( read_values1[i], read_values1[i+1])
                    #print "Parameter read from register : ", hex(index), "is : ", parameter_list1[index] ,"\n"
                    index = index + 1
   #read parameter list 2 & 3 in a similar way
            error = 0
            return error, parameter_list1, parameter_list2, parameter_list3, int(time.time())
    except IOError or ValueError:
            print "got error"
            error = 1
            return error, parameter_list1, parameter_list2, parameter_list3, int(time.time())

此外，我已经编写了一个单独的代码来将所有数据转储到服务器，如下所示：

import time
from pymongo import MongoClient

client = MongoClient('mongodb://10.32.36.40:27017')
db = client.clytics
collection = db['raspberry_pi']



 def pushData(error, value1, value2, value3, value4):
    if error == 0 :
            temp_js = {
            #variable assignment
            }
            temp_js_id = collection.insert(temp_js)

使用上面的两个代码，我为每个函数创建了线程。我只执行这段代码，执行 20 分钟后，出现值错误，程序不再执行。主要程序如下：

  import time
  from threading import Thread
  from threading import Timer
  from Queue import Queue
  from modbus import sdm630
  from dumpInDB import pushData
  from processData import process_the_data

  DELAY_SEC = 1
  DELAY_MIN = 60
  LOOP_LIMIT = 60


  def getData(q):
    error, parameter_list1, parameter_list2 , parameter_list3, parameter_list4= sdm630()
    print "In getData - data:", parameter_list1, parameter_list2
    q.put([error, parameter_list1, parameter_list2, parameter_list3, parameter_list4])

  def processData(q1,q2):
    sec_data = q1.get()
    min_data =  process_the_data(sec_data)
    print "In processData - data:", sec_data, min_data
    q2.put(min_data)
    print "queue:", q2.qsize()

 def putData(q):
    #print "In putData - data:", value[0], value[1], value[2]
    for i in range(0, q.qsize()):
            value = q.get()
            print "In putData - data:", value[0], value[1], value[2], value[3]
            pushData( value[0], value[1] , value[2], value[3] , value[4])

 def thread1(threadName, q):
    i = 0
    while 1:
            t = Timer( DELAY_SEC, getData, args = (q,))
            t.start()
            time.sleep(DELAY_SEC)

 def thread2( threadName, q1,q2):
    i = 0
    print "in thread2"
    while 1:
    t = Timer( DELAY_SEC, processData,  args = (q1,q2,))
            t.start()
            time.sleep(DELAY_SEC)

 def thread3( threadName, q):
    i = 0
    print "in thread3"
    while 1:
            t = Timer( DELAY_MIN, putData, args =  (q,))
            t.start()
            print "schedule time - min"
            time.sleep(DELAY_MIN)


  queue_second = Queue()
  queue_minute = Queue()
  thread1 = Thread( target=thread1, args=("Thread-1", queue_second) )
  thread2 = Thread( target=thread2, args=("Thread-2", queue_second,      queue_minute) )
  thread3 = Thread( target=thread3, args=("Thread-3", queue_minute) )

  thread1.start()
  thread2.start()
  thread3.start()
  thread1.join()
  thread2.join()
  thread3.join()

我遇到了这个错误。如下所示：

  minimalmodbus.Instrument<id=0xb6b2d9b8, address=2, mode=rtu,          close_port_after_each_call=True, precalculate_read_size=True, debug=False, serial=Serial<id=0xb6b482f0, open=False>(port='/dev/ttyUSB0', baudrate=9600, bytesize=8, parity='N', stopbits=1, timeout=5, xonxoff=False, rtscts=False, dsrdtr=False)>
  Traceback (most recent call last):
  File "topScript.py", line 7, in <module>
  from modbus import sdm630
  File "/home/pi/scripts/modbus.py", line 60, in <module>
sdm630()
 File "/home/pi/scripts/modbus.py", line 32, in sdm630
 read_values1  = energy_meter.read_registers( 0 , 0x24, 4)
   File "/usr/local/lib/python2.7/dist-packages/minimalmodbus.py", line 498, in read_registers
   numberOfRegisters=numberOfRegisters, payloadformat='registers')
    File "/usr/local/lib/python2.7/dist-packages/minimalmodbus.py", line 697, in _genericCommand
    payloadFromSlave = self._performCommand(functioncode, payloadToSlave)
    File "/usr/local/lib/python2.7/dist-packages/minimalmodbus.py", line 798, in _performCommand
    payloadFromSlave = _extractPayload(response, self.address, self.mode, functioncode)
   File "/usr/local/lib/python2.7/dist-packages/minimalmodbus.py", line 1075, in _extractPayload
   raise ValueError(text)
   ValueError: Checksum error in rtu mode: '\xa6\xe6' instead of '\xf7[' .    The response is: '\xff\xf7HCeN\xce\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00?\x80\x00\x00?\x80\x00\x00?\x80\x00\x00\xa6\xe6' (plain response: '\xff\xf7HCeN\xce\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\

有时值错误不断弹出一段时间，最后失败并给出一条消息说不能再创建线程。（达到最大级别）

Answer 1

你处理多个异常的语法是错误的。使用类似于：

除了 (ValueError, IOError):

有关详细信息，请参阅 Python 教程 https://docs.python.org/2/tutorial/errors.html

如何处理 while 1 循环中的值错误并使用定时器 class 进行调度

how to handle value errors in while 1 loop with scheduling it with a Timer class

json

python-2.7

raspberry-pi

modbus