Question

我有一个网站和一个USB RFID阅读器。 python脚本监视与rfid阅读器的USB连接。如果在脚本的开头未连接阅读器，则网站内容向右滑动，并显示说明连接rfid阅读器的usb电缆的说明。如果已连接，它将向左滑动，并向用户显示使用rfid卡进行身份识别。当视口中有某些内容时，阅读器应仅开始读取rfid数据。但是我无法执行此步骤，因为串行通信似乎被阻止。

import serial 
import mysql.connector
import time
import datetime
from serial.tools import list_ports
from selenium import webdriver
from selenium.webdriver.firefox.firefox_binary import FirefoxBinary
from selenium.webdriver.firefox.options import Options
from selenium.webdriver.common.keys import Keys
capabilities = webdriver.DesiredCapabilities().FIREFOX
capabilities["marionette"] = True
binary = FirefoxBinary('C:/Program Files/Mozilla Firefox/firefox.exe')
driver = webdriver.Firefox(firefox_binary=binary, capabilities=capabilities, executable_path="C:/Python37x64/geckodriver.exe")

# ------------------ USB monitorloop -------------------------------------

stop = 0
swipe = 0
driver.get('https://website.php')
while True:
    try:
        myports = [tuple(p) for p in list(serial.tools.list_ports.comports())]
        arduino_port = [port for port in myports if 'COM3' in port ][0]
        def check_presence(correct_port, interval=0.1):
        global swipe
        global stop
            while True:
                myports = [tuple(p) for p in list(serial.tools.list_ports.comports())]
                if arduino_port not in myports:
                    stop = 1
                    swipe = swipe + 1
                    if swipe == 1:
                        print ("Arduino has been disconnected!")
                        driver.execute_script("$('.in_viewport,#usb_connect, #header_usb_connect').animate({ left: '+='+'100vw'});");
                        time.sleep(1.0)
                    else:
                        continue
                else:
                    if swipe >= 1 and stop == 1:
                        swipe = 0
                        print ("Arduino connected!")
                        driver.execute_script("$('.in_viewport,#usb_connect, #header_usb_connect').animate({ left: '-='+'100vw'});");
                        time.sleep(1.0)
                    else:
                        continue
        import threading
        port_controller = threading.Thread(target=check_presence, args=(arduino_port, 0.5,))
        port_controller.setDaemon(True)
        port_controller.start()
        break
    except:
        stop = 1
        if swipe == 0:
            print("Connect USB cable")
            driver.execute_script("$('.in_viewport,#usb_connect, #header_usb_connect').animate({ left: '+='+'100vw'});");
            time.sleep(1.0)
            swipe = 1
            continue
        else:
            time.sleep(1.0)


# --------- connecting to COM 3 and database -----------------------
device_port = 'COM3'
baud = 9600
while True:
    try:
        print ("Trying...",device_port)
        connect_arduino = serial.Serial(device_port, baud)
        print ("Successfully connected to",device_port)
        print ("Try to connect to database")
        db = mysql.connector.connect(host="",port="",user="",passwd="",db="") 
        print ("Successfully connected to database")
        break
    except mysql.connector.Error as err:
        print("Something went wrong: {}".format(err))
        print ("failed to connect to database")
        time.sleep(1)
        continue
# ------- reading the card identification number and current time -------------        
while True:
    try:
        print ("Reading USB device")
        rfid_data = connect_arduino.readline()
        now = datetime.datetime.now()
        print (rfid_data.decode('utf-8'),"read on", now.strftime("%d-%m-%Y"), "at", now.strftime("%H:%M:%S"))
        time.sleep(2)
        break
    except:
        time.sleep(2)
        continue

我希望能够serial.readline() rfid_data，但我认为监视器循环正在阻止串行端口以及与端口的通信。

Answer 1

我认为您最大的问题是阅读循环中的break语句。它正在按预期方式工作并破坏了正常的循环流程，因此您只需调用一次串行端口读取功能。

改善循环的一种方法是检查RX缓冲区是否为空：

while True:
    if connect_arduino.inWaiting() != 0:
        print ("Reading USB device")
        rfid_data = connect_arduino.readline()
        now = datetime.datetime.now()
        print (rfid_data.decode('utf-8'),"read on", now.strftime("%d-%m-%Y"), "at", now.strftime("%H:%M:%S"))

如果仅在确定缓冲区中将有数据并且您知道RFID读取器将readline()作为终止字符发送时才调用\r\n，请确保您将始终读取标签。

编辑：看来您要嗅探的是端口。您不能直接从两个不同的应用程序中打开同一端口。如果您使用的是Windows，则可以尝试this solution。

Answer 2

很抱歉在这里介绍了基础知识，但是您是否检查过可以使用终端仿真器读取其他端口的串行端口？

我在串行端口（尤其是USB版本）上遇到了无尽的问题。当我不想要它时，可能是其他原因抢占了该端口，或者是由于将USB映射到COM号而出现了某些行为。有时您需要其他一些条件来仔细检查它们。

Windows上的Python串行：读取串行信息时，USB监视器循环不起作用

2 个答案: