Python(基于Pyusb)与C#(基于LibUsbDotNet)USB通信速度对比

电玩女神 2023-10-13 21:11 15阅读 0赞

# 1、实验背景 #

项目需求：下位机ZYNQ，需设计上位机与其通信，通信协议USB2.0。ZYNQ端固定Buffer长度为16k，即上位机向ZYNQ发送任意数据，ZYNQ每次反馈16k长度buffer。现对Python(基于Pyusb)与C\#(基于LibUsbDotNet)的USB通信速度进行实验，实验结果见文章末尾

# 2、Bus Hound #

Bus Hound超级软件总线协议分析器，在本实验中用于捕捉USB输入输出的协议包，以确保上位机与下位机通信正常

![在这里插入图片描述][94e714819e954c9383049b8428212c38.png_pic_center]

# 3、C\# USB读写 #

C\#使用LibUsbDotNet(LibUsbDotNet是一个.NET C\#的USB库，适用于WinUsb,libusb-win32,Linux libusb v1.x)实现USB读写，如图所示：

![在这里插入图片描述][ffefd2f155404f729ceed4876c8ee7ca.png_pic_center]  
具体代码如下：

using System;
    using System.Text;
    using System.Text.RegularExpressions;
    using LibUsbDotNet;
    using LibUsbDotNet.Main;
    
    namespace Examples
    {
        
        internal class ReadWrite
        {
        
            public static UsbDevice MyUsbDevice;
    
            #region SET YOUR USB Vendor and Product ID!
    
            public static UsbDeviceFinder MyUsbFinder = new UsbDeviceFinder(0x04b4, 0x00f0);
    
            #endregion
    
            public static void Main(string[] args)
            {
        
                ErrorCode ec = ErrorCode.None;
    
                try
                {
        
                    // Find and open the usb device.
                    MyUsbDevice = UsbDevice.OpenUsbDevice(MyUsbFinder);
    
                    // If the device is open and ready
                    if (MyUsbDevice == null) throw new Exception("Device Not Found.");
    
                    // If this is a "whole" usb device (libusb-win32, linux libusb)
                    // it will have an IUsbDevice interface. If not (WinUSB) the 
                    // variable will be null indicating this is an interface of a 
                    // device.
                    IUsbDevice wholeUsbDevice = MyUsbDevice as IUsbDevice;
                    if (!ReferenceEquals(wholeUsbDevice, null))
                    {
        
                        // This is a "whole" USB device. Before it can be used, 
                        // the desired configuration and interface must be selected.
    
                        // Select config #1
                        wholeUsbDevice.SetConfiguration(1);
    
                        // Claim interface #0.
                        wholeUsbDevice.ClaimInterface(0);
                    }
    
                    // open read endpoint 1.
                    UsbEndpointReader reader = MyUsbDevice.OpenEndpointReader(ReadEndpointID.Ep01);
    
                    // open write endpoint 1.
                    UsbEndpointWriter writer = MyUsbDevice.OpenEndpointWriter(WriteEndpointID.Ep01);
    
                    // Remove the exepath/startup filename text from the begining of the CommandLine.
                    string cmdLine = Regex.Replace(
                        Environment.CommandLine, "^\".+?\"^.*? |^.*? ", "", RegexOptions.Singleline);
    
                    if (!String.IsNullOrEmpty(cmdLine))
                    {
        
                        int bytesWritten;
                        ec = writer.Write(Encoding.Default.GetBytes(cmdLine), 2000, out bytesWritten);
                        if (ec != ErrorCode.None) throw new Exception(UsbDevice.LastErrorString);
    
                        byte[] readBuffer = new byte[16384];
                        while (ec == ErrorCode.None)
                        {
        
                            int bytesRead=4096;
    
                            // If the device hasn't sent data in the last 100 milliseconds,
                            // a timeout error (ec = IoTimedOut) will occur. 
                            for(int i=0; i<2500;i++)
                            {
        
                                ec = reader.Read(readBuffer, 100, out bytesRead);
                            }
    
    
                            if (bytesRead == 0) throw new Exception("No more bytes!");
    
                            // Write that output to the console.
                            Console.Write(Encoding.Default.GetString(readBuffer, 0, bytesRead));
                        }
    
                        Console.WriteLine("\r\nDone!\r\n");
                    }
                    else
                        throw new Exception("Nothing to do.");
                }
                catch (Exception ex)
                {
        
                    Console.WriteLine();
                    Console.WriteLine((ec != ErrorCode.None ? ec + ":" : String.Empty) + ex.Message);
                }
                finally
                {
        
                    if (MyUsbDevice != null)
                    {
        
                        if (MyUsbDevice.IsOpen)
                        {
        
                            // If this is a "whole" usb device (libusb-win32, linux libusb-1.0)
                            // it exposes an IUsbDevice interface. If not (WinUSB) the 
                            // 'wholeUsbDevice' variable will be null indicating this is 
                            // an interface of a device; it does not require or support 
                            // configuration and interface selection.
                            IUsbDevice wholeUsbDevice = MyUsbDevice as IUsbDevice;
                            if (!ReferenceEquals(wholeUsbDevice, null))
                            {
        
                                // Release interface #0.
                                wholeUsbDevice.ReleaseInterface(0);
                            }
    
                            MyUsbDevice.Close();
                        }
                        MyUsbDevice = null;
    
                        // Free usb resources
                        UsbDevice.Exit();
    
                    }
    
                    // Wait for user input..
                    Console.ReadKey();
                }
            }
        }
    }

注意此代码 byte\[\] readBuffer = new byte\[16384\]，readBuffer的大小决定reader.Read(readBuffer, 100, out bytesRead)中bytesRead大小，故此大小要根据实验进行调整。 int bytesRead=4096，该值不为0即可，如果至小于byte\[\] readBuffer = new byte\[16384\]中readBuffer的大小，其不直接影响reader.Read(readBuffer, 100, out bytesRead)中bytesRead大小

# 4、Python USB读写 #

Python使用Pyusb实现USB读写，如图所示：

![在这里插入图片描述][89f3ac2e4db44fd7b7e322e28d577918.png_pic_center]  
详细代码如下：

import usb.core
    import time
    
    def find_usb_dev():
        all_devs = usb.core.find(find_all = True)
        for dev in all_devs:
             print(dev)
    
    def usb_dev_enabled(dev):
        while(True):
            try:
                dev.set_configuration()
                break
            except Exception as e:
                print(e)
    
    def usb_dev_write_bulk_out_ep(dev, endpoint, data, timeout):
        while(True):  
            try:
                data = dev.write(endpoint, data, timeout)
                break
            except Exception as e:
                print(e)
        return data
    	
    def usb_dev_read_bulk_in_ep(dev, endpoint, buffer_len, timeout):
        while(True):  
            try:
                data = dev.read(endpoint, buffer_len, timeout)
                break
            except Exception as e:
                print(e)
        return data
    
    
    def read_dev():
        dev =  usb.core.find(idVendor= 0x04b4, idProduct= 0x00f0)
        # print(dev)
        data1 = bytes.fromhex('7e 7e')
        send1 = usb_dev_write_bulk_out_ep(dev, 0x1, data1, 2000)
        time_start = time.time()
        for i in range(10000):
            rev1 = usb_dev_read_bulk_in_ep(dev, 0x81,4096, 100)
        time_end = time.time()
        print(time_end - time_start)
    
    if __name__ == "__main__":
    
        #### 普通
        read_dev()

# 5、USB通信速度 #

最终实验结果如下表，综合来看Python(基于Pyusb)与C\#(基于LibUsbDotNet)的USB通信速度大体相同，但是Python的循环效率远低于C\#，导致read次数多时，read时间大

<table> 
 <thead> 
  <tr> 
   <th>上位机read次数</th> 
   <th>read buffer长度</th> 
   <th>C#所需时间(s)</th> 
   <th>Python所需时间(s)</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>80000</td> 
   <td>512</td> 
   <td>2.587</td> 
   <td>5.047</td> 
  </tr> 
  <tr> 
   <td>40000</td> 
   <td>1024</td> 
   <td>2.692</td> 
   <td>3.038</td> 
  </tr> 
  <tr> 
   <td>10000</td> 
   <td>4096</td> 
   <td>2.504</td> 
   <td>2.506</td> 
  </tr> 
  <tr> 
   <td>20000</td> 
   <td>4096</td> 
   <td>5.004</td> 
   <td>5.001</td> 
  </tr> 
  <tr> 
   <td>10000</td> 
   <td>8192</td> 
   <td>5.102</td> 
   <td>5.001</td> 
  </tr> 
  <tr> 
   <td>2500</td> 
   <td>16384</td> 
   <td>2.615</td> 
   <td>2.569</td> 
  </tr> 
  <tr> 
   <td>10000</td> 
   <td>16384</td> 
   <td>10.837</td> 
   <td>10.295</td> 
  </tr> 
 </tbody> 
</table>

**希望本文对大家有帮助，上文若有不妥之处，欢迎指正**

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[94e714819e954c9383049b8428212c38.png_pic_center]: https://img-blog.csdnimg.cn/94e714819e954c9383049b8428212c38.png#pic_center
[ffefd2f155404f729ceed4876c8ee7ca.png_pic_center]: https://img-blog.csdnimg.cn/ffefd2f155404f729ceed4876c8ee7ca.png#pic_center
[89f3ac2e4db44fd7b7e322e28d577918.png_pic_center]: https://img-blog.csdnimg.cn/89f3ac2e4db44fd7b7e322e28d577918.png#pic_center