MatLab interfacing issue

Using Arduino Interfacing w/ Software on the Computer
1

I want to transmit data from MatLab to the arduino. I am troubleshooting using a code for the arduino from another thread as follows:

int pLED = 7;
int val= 0;
char inData[10];
int index;
boolean started = false;
boolean ended = false;

void setup()
{
  Serial.begin(9600);
  pinMode(pLED, OUTPUT);
}
void loop()
{
}

void serialEvent()
{
  while(Serial.available())
  {
      char aChar = Serial.read();
      if(aChar == '<')
      {
          started = true;
          index = 0;
          inData[index] = '\0';
      }
      else if(aChar == '>')
      {
          ended = true;
      }
      else if(started)
      {
          inData[index] = aChar;
          index++;
          inData[index] = '\0';
      }
  }

  if(started && ended)
  {
      // Convert the string to an integer
      int inInt = atoi(inData);
      // Use the value

      // Get ready for the next time
      started = false;
      ended = false;

      index = 0;
      inData[index] = '\0';
      
      for (int i=0; i<inInt; i++)
  {
    digitalWrite(pLED, HIGH);
    delay(100);
    digitalWrite(pLED, LOW);
    delay(100);
  }
  }
  
  
}

My MatLab code is

%% ARDUINO INTERFACING

% Connect to Arduino the specified port
Port = '/dev/tty.usbmodem1421';
BaudRate = 9600;
DataBits = 8;

% Create the serial connection and open communication with the Arduino.
ser = serial(Port);
set(ser, 'BaudRate', BaudRate);
set(ser, 'DataBits', DataBits);
pause(0.02);
fopen(ser);
pause(0.5); 

pause(0.02);
value = 10;
fprintf(ser, '>');
fprintf(ser, '6');
fprintf(ser, '<');
pause(0.02);

fclose(ser);
delete(ser);
clear ser;
delete(instrfindall);

This will only work after opening the serial monitor in the arduino window. If it hasn't been opened, the RX light on the arduino will flash but my output LED doesn't flash. Once the serial monitor has been opened it will work once, but afterwards throws up an error that the serial port is being used by another application. I am assuming there is some sort of initialising issue that opening the serial monitor in the arduino fixes?

Thanks in advance

2

I don't know Matlab but your symptom suggests that Matlab is not waiting for the Arduino to reset after the seial port is opened.

Have a look at how this is handled in this Python demo. The same principles should be relevant in Matlab.

You may also be interested in the examples in serial input basics

...R

3

Thanks for your reply. I tried adding a while loop to wait for a message from the arduino, as in your example but the while loop never exits. I know you aren't familiar with MatLab but for any others who are I added:

w = '';
while strcmp('<Ready>',w) == 0
      w = fscanf(ser, '%s');
end

Where is sent at the end of the setup from the arduino and successfully displays in the serial monitor. Is this likely an issue with the MatLab code as opposed to the arduino code?

4

Is this likely an issue with the MatLab code

Yes. If you need to open the Serial Monitor application, and close it, in order to get MatLab to talk to the Arduino, then, clearly, MatLab isn't opening the serial port correctly.

Which Arduino are you using? For Leonardos, for instance, DTREnable must be set to true. For UNOs, that isn't necessary.

5

@ PaulS. Thanks for your reply, I am using the UNO. Still no luck but I will try the MatLab forums.