How to read from a usb rfid reader?

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悲&欢浪女
悲&欢浪女 2021-01-03 07:42

I have bought a usb rfid reader. How can I read data when user puts an rfid tag in front of the device?

my computer identifies the device as an Human Interface Devic

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  • 2021-01-03 08:13

    If they have given you a SDK with your reader then use it. otherwise you will have to know the hex commands of your reader.Send commands to reader and get response

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  • 2021-01-03 08:16

    This is what I did when I had the same problem.

    using System;
    using System.Text;
    using LibUsbDotNet;
    using LibUsbDotNet.Main;
    
    namespace Examples
    {
    internal class ReadPolling
    {
        public static UsbDevice MyUsbDevice;
    
        #region SET YOUR USB Vendor and Product ID!
    
        public static UsbDeviceFinder MyUsbFinder = new UsbDeviceFinder(1234, 1);
    
        #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-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))
                {
                    // 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);
    
    
                byte[] readBuffer = new byte[1024];
                while (ec == ErrorCode.None)
                {
                    int bytesRead;
    
                    // If the device hasn't sent data in the last 5 seconds,
                    // a timeout error (ec = IoTimedOut) will occur. 
                    ec = reader.Read(readBuffer, 5000, out bytesRead);
    
                    if (bytesRead == 0) throw new Exception(string.Format("{0}:No more bytes!", ec));
                    Console.WriteLine("{0} bytes read", bytesRead);
    
                    // Write that output to the console.
                    Console.Write(Encoding.Default.GetString(readBuffer, 0, bytesRead));
                }
    
                Console.WriteLine("\r\nDone!\r\n");
            }
            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();
            }
        }
      }
    }
    

    Opens a USB device by vendor and product id.

    Opens a UsbEndpointReader class for reading.

    Reads and displays usb device output from Ep01 until no data is received for 5 seconds.

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  • 2021-01-03 08:21

    Please see: How do I read input from a USB HID device?

    The device might enumerate as generic HID but might behave like a keyboard. If so, it should just type out the characters it reads. If not, you'll have to poll it from the driver. That link should help.

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