I would like to establish a communication between my C# program and my Arduino Duemilanove. I tried lot of different tutorials, but none of them were the same, and I'm a little bit confused.

Actually my code is:


using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO.Ports;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace InterfaceArduinoWindowsFOrm {
  public partial class Form1 : Form {
    public Form1() {
      serialPort1.PortName = "COM3";
      serialPort1.BaudRate = 9600;

    private void pictureBox1_Click(object sender, EventArgs e) {

    private void tabPage2_Click(object sender, EventArgs e) {

    private void listBox1_SelectedIndexChanged(object sender, EventArgs e) {

    private void toolTip1_Popup(object sender, PopupEventArgs e) {

    private void notifyIcon1_MouseDoubleClick(object sender, MouseEventArgs e) {

    private void button1_Click_1(object sender, EventArgs e) {


/* Sweep
  by BARRAGAN <http://barraganstudio.com>
  This example code is in the public domain.
  modified 8 Nov 2013
  by Scott Fitzgerald

#include <Servo.h>

Servo myservo;  // Create servo object to control a servo.
// Twelve servo objects can be created on most boards.
int pos = 0;
int message = 0; // This will hold one byte of the serial message
                 // variable to store the servo position.

void setup() {
  myservo.attach(9);  // Attaches the servo on pin 9 to the servo object

void loop() {
  if (Serial.available()) {

    // Check to see if there is a new message
    message = Serial.read();

    // Put the serial input into the message

    if (message == '5') {
      for(pos = 0; pos <= 180; pos += 1) {
        // Goes from 0 degrees to 180 degrees
        // in steps of 1 degree

        // Tell servo to go to position in variable 'pos'

        // Waits 15 ms for the servo to reach the position

      for(pos = 180; pos>=0; pos-=1) {
        // Goes from 180 degrees to 0 degrees

        // Tell servo to go to position in variable 'pos'

        // Waits 15 ms for the servo to reach the position

The problem is, when I click my button, nothing happens, but obviously if I remove the if statement, the servo motor code works.

  • Did you make sure that the C# button event is fired, and that the Serial connection is established properly? Also, what happens if you open the Arduino COM terminal and press 5? – Omer Dec 2 '14 at 6:22
  • Hum yea , i tested with some console writte and Button work , what do you mean by : press 5? – War-sloop Dec 2 '14 at 6:24
  • I mean that, in your C# code, you just send "5" to the serial port. As part of the debugging - pin pointing where the problem lays - did you use the Arduino Serial console to send "5" the same way you send it from C#, and made sure it works there? Because if sending "5" from the Serial console in the Arduino IDE doesn't work, the C# way won't work either. – Omer Dec 2 '14 at 7:36
  • I follow lot of tutoriel covering this , the code is really similar as mine , but , when I try to use the serial monitor , and I try to fire button event , it say that Com3 is already in use and unauthorized ... 5 is only a message id to call the arduino IF statement .... – War-sloop Dec 2 '14 at 8:01
  • Yes, I get that 5 is the trigger. What I'm trying to understand is whether that trigger works or not. You cannot use Arduino IDE Serial Monitor while running your C# code since the Arduino COM port can interface only one serial port at a time. Try using the Arduino IDE Serial Monitor after closing the C# serial port and not in parallel to it. – Omer Dec 2 '14 at 8:50

Since you are sending from the Arduino the received serial data back to the C# application (Serial.print(message);), I would advise to check what you receive on the C# side. Register to the DataReceived event of the SerialPort as so:

serialPort1.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);

And add an event handler:

private void DataReceivedHandler(object sender, SerialDataReceivedEventArgs e)
    SerialPort port = (SerialPort)sender;
    string data= port.ReadExisting();
    // check here what data you received, if any

This way you could confirm that the Arduino gets the data properly from the C# side to begin with. Next step would be to understand if this if statement treats the data properly:

if (message == '5')

But starting from examination of what you get from the C# side will help you decide where exactly is the problem.

  • EDIT : NeverMind I missundarstood your post i'm sorry, But i acctualy don't understand your answer, do you mean that I try to send from Arduino to C# because, Me I want to do the opposite... – War-sloop Dec 8 '14 at 9:54
  • Yes, I mean that you try send from Arduino to C# (you are already doing that) and see what you get. This will help you understand where is the problem. – Omer Dec 9 '14 at 19:33
  • Ok so i Will try if i understand to directly send from arduino to c# – War-sloop Dec 9 '14 at 21:04
  • You are already doing it... the line "Serial.print(message);" sending the message back to the C# code. Just see what you get from the C# side as I explained. – Omer Dec 9 '14 at 21:12
  • Hooo yea it was a test code , but I forget to read from C# I'm sorry if I didn't understand but it's because I forget this line ... – War-sloop Dec 10 '14 at 5:58

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