C#中最快的串口通信？

Question

I am new at this forum and I do not have many experiences with programming in C#. I have build simple Windows application in C# to communicate with some electronic board that my friend gave it to me. He has defined serial port baud rate in microcontroller at 38400. I want to send and receive bytes via serial port as fast as possible. With existing serialport tool in C# I was able only to read bytes but still not fast enough even with eventhandler in its own thread. My buffer[4096] was full in few seconds.

My question is if there exist some other functions or tools for serial port communication that does not use so much processor time. I need to read one byte in less than 200 us. I have more experiences with embedded systems where this was not a problem.

Thanks everyone for some advice or idea.

Tomaž

Answer 1

thanks for all replies. I can read all bytes coming from board, but I can not reply fast enough. Here is my code. I have used an event for reading buffer. If I try to reply in event the next bytes contains wrong values.

#region namespace usings
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

using System.IO;
using System.IO.Ports;
using System.Threading;
using System.Runtime.InteropServices;
using System.Diagnostics;

using Microsoft.Win32;
using Zaber.Serial.Core;
using Diagnostics = System.Diagnostics;
#endregion

namespace Lucifire_aplication {

public partial class Form1 : Form
{


    int k = 1;
    string number_of_bytes;
    byte checksum;
    byte[] buffer = new byte[11];
    byte[] buffer_old = new byte[11];


    public Form1()
    {
        InitializeComponent();
        configure_button.Enabled = false;
        start_button.Enabled = false;
        foreach (string s in SerialPort.GetPortNames())
        {
            serial_port_name.Items.Add(s);
        }
        serial_port_name.Text = "Select port";
        for (int i = 4800; i <= 38400; i = i * 2)
        {
            baud_rate.Items.Add(i);
        }
        for (int i = 57600; i <= 921600; i = i * 2)
        {
            baud_rate.Items.Add(i);
        }

        serial_port_name.DropDownStyle = ComboBoxStyle.DropDownList;
        baud_rate.SelectedIndex = 3;
        baud_rate.DropDownStyle = ComboBoxStyle.DropDownList;


    }

    private void serial_port_name_SelectedIndexChanged(object sender, EventArgs e)
    {
        if (serial_port_name.Text != "Select port")
        {
            configure_button.Enabled = true;
        }
    }

    private void configure_button_Click(object sender, EventArgs e)
    {
        serialPort1.PortName = serial_port_name.Text;
        serialPort1.BaudRate = Int32.Parse(baud_rate.Text);
        serialPort1.DataBits = 8;
        serialPort1.StopBits = StopBits.One;
        //serialPort1.Handshake = Handshake.None;
        serialPort1.ReceivedBytesThreshold = 44;
        serialPort1.ReadBufferSize = 8192;
        MessageBox.Show("Communication is set on " + serialPort1.PortName + " with baud rate: " + serialPort1.BaudRate);
        start_button.Enabled = true;
    }

    private void start_button_Click(object sender, EventArgs e)
    {
        if (serialPort1.IsOpen)
        {

            serialPort1.Close();
            start_button.Text = "START";
            read_button.Enabled = false;
            //read_write.Enabled = false;
            comport_status.Text = "DISCONNECTED";
        }
        else
        {
            serialPort1.Open();
            start_button.Text = "STOP";
            read_button.Enabled = true;
            //read_write.Enabled = true;
            comport_status.Text = "CONNECTED";
        }
    }

    private void quitToolStripMenuItem_Click(object sender, EventArgs e)
    {
        System.Windows.Forms.Application.Exit();
    }

    private void read_button_Click(object sender, EventArgs e)
    {
        bytes_to_read.Text = serialPort1.BytesToRead.ToString();
        read_data.Text = serialPort1.ReadExisting().ToString();
        read_data.Text += k.ToString() + "   ";
        if (buffer_old[0] == 4)
        {
            serialPort1.ReadByte();
        }
        serialPort1.Read(buffer, 0, 11);
        for (int j = 0; j < 11; j++)
        {
            read_data.Text += buffer[j].ToString() + "  ";
        }
        read_data.Text += "\n";
        k++;
        buffer_old = buffer;
    }

    private void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
    {

        serialPort1 = (SerialPort)sender;
        number_of_bytes = serialPort1.BytesToRead.ToString();
        if (buffer_old[0] == 4)
        {
            serialPort1.ReadByte();
        }
        serialPort1.Read(buffer, 0, 11);
        buffer_old = buffer;
        this.Invoke(new EventHandler(displaytext));
        Thread.Sleep(20);
    }

    private void displaytext(object sender, EventArgs e)
    {
        checksum = 0;
        bytes_to_read.Text = number_of_bytes;
        read_data.Text += k.ToString() + "\t";
        for (int j = 0; j < 11; j++)
        {
            read_data.Text += buffer[j].ToString() + "  ";
            checksum += buffer[j]; 
        }
        checksum -= buffer[10];
        read_data.Text += "  \t" + checksum.ToString();
        read_data.Text += "\n";
        k++;
    }

}

}

Answer 2

Please take a look at : If you must use .NET System.IO.Ports.SerialPort

Ben Voigt (the author) gives an excellent example on how to use the inherent BaseStream member of SerialPort which is more efficient for using the underlying Win32 API.

Port = new SerialPort("COM" + PORT_NUMBER.ToString()); 
...
private void ReadEvent()  
{      
    byte[] buffer = new byte[2000];  
    Action kickoffRead = null;  
    kickoffRead = (Action)(() => Port.BaseStream.BeginRead(buffer, 0, buffer.Length, delegate(IAsyncResult ar)  
    {  
        try  
        {  
            int count = Port.BaseStream.EndRead(ar);  
            byte[] dst = new byte[count];  
            Buffer.BlockCopy(buffer, 0, dst, 0, count);  
            RaiseAppSerialDataEvent(dst);  
        }  
        catch (Exception exception)  
        {  
            MessageBox.Show(ERROR == > " + exception.ToString());    
        }  
        kickoffRead();  
    }, null)); kickoffRead();  
}

Regards.