C# Arduino serial control

Projects General Guidance
1

Hi,

I have a project for which I want to implement a simple interface. I’m not very experimented when it comes to programming, so I decided on a C# WindowsFormsApp which I use to send commands to the Arduino via serial. After a bit of fumbling around, I made it work and control two LEDs.

String s_command;
String led_var;
String led_status;

int LED0 = 8;
int LED1 = 7;

void setup()
{
  Serial.begin(115200);
  pinMode(LED0, OUTPUT);
  pinMode(LED1, OUTPUT);
}

void loop()
{
  if (Serial.available())
  {
    s_command = Serial.readStringUntil('\n');

    led_var = getValue(s_command, ':', 0);
    led_status = getValue(s_command, ':', 1);

    Serial.print(led_var);
    Serial.print(":");
    Serial.print(led_status);
    Serial.println("");

    ledControl(led_var, led_status);
  }
}

String getValue(String data, char separator, int index)
{
  int found = 0;
  int strIndex[] = {0, -1};
  int maxIndex = data.length()-1;

  for(int i=0; i<=maxIndex && found<=index; i++){
    if(data.charAt(i)==separator || i==maxIndex){
        found++;
        strIndex[0] = strIndex[1]+1;
        strIndex[1] = (i == maxIndex) ? i+1 : i;
    }
  }

  return found>index ? data.substring(strIndex[0], strIndex[1]) : "";
}

void ledControl(String ledNumber, String status)
{
  if (ledNumber == "LED0")
  {
    if (status == "ON")
    {
      digitalWrite(LED0, HIGH);
    }
    if (status == "OFF")
    {
      digitalWrite(LED0, LOW);
    }
  }
  else if (ledNumber == "LED1")
  {
    if (status == "ON")
    {
      digitalWrite(LED1, HIGH);
    }
    if (status == "OFF")
    {
      digitalWrite(LED1, LOW);
    }
  }
  else
  {
    Serial.println("LED not recognized!");
  }
  
}

When I use the Serial Monitor, it works OK, but when I use the C# app, I get this short delay (about 1 sec). I assume the delay comes from one of the functions in the Arduino code, however I’m not sure which one (both probably?), or how to improve it.

From what I read, it’d be better to use C/C++ instead of the Arduino functions, but I really don’t know how to go about using those.

So, I’d appreciate some advice on how to go about improving what I cobbled together.

Thanks!

2

in your C# code are you remembering to append a '\n' to the transmitted text

s_command = Serial.readStringUntil('\n');

will timeout after 1 second if '\n' is not received, i.e. you will get a delay of 1 second on every string received if there is no terminating \n

in C# when prompting to find a modem I use

serialPort1.Write("AT\r\n");
3

Welcome to the forum

Does the C# app open and close the serial port when it sends data to the Arduino ? If so, then be aware that opening the Serial port causes most Arduinos to reboot which may be the cause of the delay

4

You said yourself it works with Serial Monitor fine meaning the code works fine

5

IIRC, 1 second is the default timeout for the "Serial.readString...()" functions. Perhaps your C# program is sending '\r' at end of line, rater than '\n', or something similar.
(as your OS gets more complex, the chances that outputting '\n' will result in something different than you expect increases, unless you've gone to some effort to prevent it ("raw mode" or similar.) I have no idea what the "normal" behavior for C#/Windows is.)

6

Yes, adding \n to the string being sent solved the delay. I think I just assumed that pressing Enter would somehow register as that character, which now thinking about it is of course not the case. I should’ve paid more attention. Thanks for the help!

7

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.