从C＃中的串行端口接收时处理大字节

Question

I am new in the serial port. Currently, my project is to extract data from the machine. I'm getting data via an event onDataReceive and the machine is sending bytes.

My problem is that the first wave of bytes seemed to be converted correctly to string but in the second batch of bytes, I got garbage data.

Screen Shot of the output(this is the output given by the multi-currency reader machine:

The garbage data is I think the Serial Nos.

Here is my code in onDataReceive method:

private void _serialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {
        while (serialPort.BytesToRead > 0)
        {
            // Initialize a buffer to hold the received data
            byte[] buffer = new byte[serialPort.ReadBufferSize];
            //// There is no accurate method for checking how many bytes are read
            //// unless you check the return from the Read method
            int bytesRead = serialPort.Read(buffer, 0, buffer.Length);
            String asd = System.Text.ASCIIEncoding.ASCII.GetString(buffer, 0, bytesRead);

            //// For the example assume the data we are received is ASCII data.
            tString += Encoding.ASCII.GetString(buffer, 0, bytesRead);
            temp += System.Text.Encoding.Unicode.GetString(buffer, 0, bytesRead);
            temp2 += System.Text.Encoding.UTF32.GetString(buffer, 0, bytesRead);
            System.IO.File.WriteAllText(@"C:\OutputTextFiles\WriteLines.txt", tString);
            System.IO.File.WriteAllText(@"C:\OutputTextFiles\WriteLines2.txt", temp);
            System.IO.File.WriteAllText(@"C:\OutputTextFiles\WriteLines3.txt", temp2);
        }
    }

I'm trying to put the output with a txt file.

I hope someone could help me in my problem. Any tips and suggestions in data handling especially bytes?

Answer 1

Without knowing the size of serialPort.ReadBufferSize I can only suspect that your buffer is breaking the encoding bytes of your string. A character can be made of one or more bytes.

The trick is to read all of the bytes before decoding the string.

Try this example program:

var encoding = System.Text.Encoding.Unicode;
var message = "I am new in serial port. Currently my project is to extract data from machine.";
using (var ms = new MemoryStream(encoding.GetBytes(message)))
{
    var bytes = new List<byte>();
    var buffer = new byte[23];
    var bytesRead = ms.Read(buffer, 0, buffer.Length);
    while (bytesRead > 0)
    {
        Console.WriteLine(encoding.GetString(buffer, 0, bytesRead));
        bytes.AddRange(buffer.Take(bytesRead));
        bytesRead = ms.Read(buffer, 0, buffer.Length);
    }
    Console.WriteLine(encoding.GetString(bytes.ToArray(), 0, bytes.Count));
}

It will output the following:

I am new in�
猀攀爀椀愀氀 瀀漀爀琀�
. Currently�
洀礀 瀀爀漀樀攀挀琀 �
is to extra�
琀 搀愀琀愀 昀爀漀洀�
 machine.
I am new in serial port. Currently my project is to extract data from machine.

The final line is correct because it uses all of the bytes to decode. The previous lines have errors because I've used a buffer size of 23 which breaks the string encoding.