usb设备批量传输如何实现流控

Question

usb设备批量传输如何实现流控？
比如按键按下不接收数据，主机等待，
按键键值反转，继续接收没接收完的数据

Answer 1

在USB设备批量传输中，流控通常是通过实现USB协议中的流控机制来实现的。

USB协议中有两个常用的流控机制：Nak（Negative Acknowledge）和Stall（拒绝）。

Nak：当USB设备不能接收主机发送的数据时，它可以发送NAK响应，表示当前不能接收数据。
Stall：当USB设备不能处理主机的请求时，它可以发送STALL响应，表示当前请求无法处理。
如果你想实现按键按下时不接收数据，可以在按键按下时发送NAK响应，等按键键值反转时再发送ACK响应。这样主机就会等待，等待按键反转后再继续接收没接收完的数据。

using System;
using System.Threading;
using Microsoft.Win32.SafeHandles;
using System.Runtime.InteropServices;

namespace UsbFlowControl
{
    class Program
    {
        static void Main(string[] args)
        {
            // Open a handle to the USB device
            SafeFileHandle deviceHandle = WinUsb_Functions.CreateFile(@"\\.\ExampleDevice",
                FileAccess.ReadWrite, FileShare.ReadWrite, IntPtr.Zero, FileMode.Open,
                WinUsb_Functions.FILE_ATTRIBUTE_NORMAL | WinUsb_Functions.FILE_FLAG_OVERLAPPED, IntPtr.Zero);

            if (deviceHandle.IsInvalid)
            {
                Console.WriteLine("Error opening handle to the USB device");
                return;
            }

            // Initialize WinUSB
            IntPtr winUsbHandle;
            bool success = WinUsb_Functions.WinUsb_Initialize(deviceHandle, out winUsbHandle);
            if (!success)
            {
                Console.WriteLine("Error initializing WinUSB");
                return;
            }

            // Get the USB device endpoint addresses
            WinUsb_Functions.WINUSB_PIPE_INFORMATION pipeIn;
            WinUsb_Functions.WINUSB_PIPE_INFORMATION pipeOut;
            success = WinUsb_Functions.WinUsb_GetPipePolicy(winUsbHandle, WinUsb_Functions.PIPE_ID.PIPE_ID_IN, out pipeIn);
            if (!success)
            {
                Console.WriteLine("Error getting input pipe policy");
                return;
            }
            success = WinUsb_Functions.WinUsb_GetPipePolicy(winUsbHandle, WinUsb_Functions.PIPE_ID.PIPE_ID_OUT, out pipeOut);
            if (!success)
            {
                Console.WriteLine("Error getting output pipe policy");
                return;
            }

            // Start the transfer loop
            byte[] buffer = new byte[64];
            Overlapped overlapped = new Overlapped();
            AutoResetEvent eventHandle = new AutoResetEvent(false);
            while (true)
            {
                // Check if the button is pressed
                if (ButtonIsPressed())
                {
                    Console.WriteLine("Button is pressed. Waiting for release...");
                    continue;
                }

                // Read data from the USB device
                overlapped.EventHandle = eventHandle.