C#讀取USB RFID資料問題使用LibUsbDotNet

Question

ErrorCode ec = ErrorCode.None; 
UsbEndpointReader reader = MyUsbDevice.OpenEndpointReader(ReadEndpointID.Ep01);
byte[] readBuffer = new byte[128];
while (ec == ErrorCode.None)
    {
         int bytesRead;
         ec = reader.Read(readBuffer,1000, out bytesRead);

         if (bytesRead == 0) throw new Exception(string.Format("{0}:No more bytes!", ec));
         Console.WriteLine("{0} bytes read", bytesRead);
         Console.Write(Encoding.Default.GetString(readBuffer));         
}
                    

當我的RFID讀取器讀取時，讀取數據確實有可讀取到，但若讀取數據無法填充滿byte[128]時，讀取將回報超時，將數據量需求成byte[64]又會讀不到全部的資料，byte[X]的X資料輸入非2的次數進行讀取時回報超時 ， 查看 bytesRead 輸出都是 0， LibUsbDotNet 的 UsbEndpointReader.Read 寫得相當的簡化，我搞不清楚他是怎麼運作的，還請大家解惑。

Answer 1

參考既有討論修改你的迴圈

https://social.msdn.microsoft.com/Forums/zh-TW/home?sort=relevancedesc&brandIgnore=True&searchTerm=MemoryStream%2BBuffer

---

不精確的問法，就會得到隨便猜的答案；自己都不肯花時間好好描述問題，又何必期望網友會認真回答？

Answer 2

                    byte[] readBuffer = new byte[160];
                    while (true)//ec == ErrorCode.None)
                    {
                        int bytesRead;

                        ec = reader.Read(readBuffer,5000, out bytesRead);

                        byte[] readBuffer2 = new byte[10];
                        int count = 0;
                        for (int i = 0; i < readBuffer.Length; i++)
                        {
                            if (readBuffer[i] != 0)
                            {
                                readBuffer2[count] = (byte)(readBuffer[i]+19);
                                if (readBuffer2[count] == 58) readBuffer2[count] = 48;
                                count++;

                            }
                        }
                        Console.Write(Encoding.Default.GetString(readBuffer2) + "\r\n");
                    }

                }

當我把byte[]中的數字更改成160後，ec的回覆就恢復正常了。

Answer 3

看了裡面的一些文章的理解是，我其實只要把讀取長度改短並讓程式多迴圈幾次就可以解決了像是

byte[] readBuffer = new byte[256];
                    while (true)
                    {
                        int bytesRead,x=0;
                        ec = reader.Read(readBuffer, 0, 16, 100, out bytesRead);
                        if (bytesRead == 0) Console.Write(("{0}:No more bytes!", ec,"\r\n"));
                        else for (int i = 16; x < 9; x++,i+=16) ec = reader.Read(readBuffer, i, 16, 100, out bytesRead);

                        if (x >= 9)
                        {
                            byte[] readBuffer2 = new byte[10];
                            int count = 0;
                            for (int i = 0; i < readBuffer.Length; i++)
                            {
                                if (readBuffer[i] != 0)
                                {
                                    readBuffer2[count] = (byte)(readBuffer[i] + 19);
                                    if (readBuffer2[count] == 58) readBuffer2[count] = 48;
                                    count++;

                                }
                            }
                            Console.Write(Encoding.Default.GetString(readBuffer2) + "\r\n");
                            Thread.Sleep(100);
                        }
                    }

測試過也沒什麼問題，感謝指點。