如何检查设备是否已连接 [英] How to check if device is connected Pyserial

问题描述

我正在通过USB端口与Arduino连接，并使用PySerial模块向其发送数据.首先，我可以使用以下代码检查设备是否已连接:

I am connecting with my Arduino through a USB port and sending data to it by using PySerial module. At first I can check if the device is connected by using this code:

try:
    ser = serial.Serial("COM3", 9600)
except serial.serialutil.SerialException:
    print "Arduino not connected"

现在我要做的是定期检查Arduino是否仍连接到计算机.我尝试了ser.isOpen()，但这即使Arduino断开连接也返回true.我也想知道如何重新连接设备.我的意思是，一旦断开设备的连接，程序将无法再向Arduino发送任何数据.

Now what I want to do is to check periodically if the Arduino is still connected to the computer. I tried ser.isOpen() but this returns true even if the Arduino is disconnected. I would also like to know how to reconnect the device. I mean once you disconnect the device the program can no longer send any data to Arduino.

推荐答案

大多数答案提出2种方法:

Most of the answers propose 2 approaches:

1. 在代码的某些地方，通过串行发送某种消息，以检查您的设备是否仍然有效
2. 启动一个单独的线程，并通过打开通信来连续检查设备是否处于活动状态

第一个解决方案的问题是不是总是检查连接，而是仅检查某些特定点:此解决方案不是很好，如果写得不好甚至可能无法正常工作

The problem with the first solution is that you are not always checking the connection, but only checking in some specific points: this solution isn't very elegant and if badly written could even be not working.

第二种解决方案解决了第一种解决方案的问题，但引入了一个新问题:在线程循环中检查连接或最差的发送消息会导致问题，甚至可能中断其他功能与设备的连接.

The second solution solves the problem of the first solution, but introduces a new problem: checking the connection, or worst sending a message, in a threaded loop will cause problem or may even interrupt the connection to the device from other functions.

一种解决方案，允许您不断检查连接而不会独占通信，这涉及读取现有的COM:

A solution that allows you to constantly check the connection without monopolizing the communication involves the reading of the existing COM:

import serial.tools.list_ports
myports = [tuple(p) for p in list(serial.tools.list_ports.comports())]
print myports

输出:

[(u'COM3', u'Arduino Due Programming Port (COM3)', u'some more data...'),
(u'COM6', u'USB Serial Port (COM6)', u'some more data...'),
(u'COM100', u'com0com - serial port emulator (COM100)', u'some more data...')]

然后我们保存包含端口的元组:

then we save the tuple that contains our port:

arduino_port = [port for port in myports if 'COM3' in port ][0]

然后我们创建一个函数来检查该端口是否仍然存在:

then we create a function that checks if this port is still present:

import time

def check_presence(correct_port, interval=0.1):
    while True:
    myports = [tuple(p) for p in list(serial.tools.list_ports.comports())]
    if arduino_port not in myports:
        print "Arduino has been disconnected!"
        break
    time.sleep(interval)

最后，我们将此功能作为守护线程运行:

At last, we run this function as a daemon thread:

import threading
port_controller = threading.Thread(target=check_presence, args=(arduino_port, 0.1,))
port_controller.setDaemon(True)
port_controller.start()

通过这种方式，您将每隔0.1秒检查arduino是否仍处于连接状态，并且当arduino断开连接或所有其他活动均已结束时，线程将结束

in this way, you'll check each 0.1 secs if the arduino is still connected, and the thread will end when arduino is disconnected or all other activities have ended

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