how to send serial data using loop to arduino.

i have tried the following code in matlab, there are no errors, the command window is showing correct answers but the leds at pin 11,12 which I put on the arduino are not glowing.

one more thing is---->the RX led in glowing contineously.

what would might be the problem, why my leds at pins 11,12 are not glowing contineously.

somebody please help

///////////////////////////////////////////////////

clear all

clc

delete(instrfindall)

arduino=serial('COM5','BaudRate',9600); % create serial communication object on port COM5

fopen(arduino); % initiate arduino communication

while 1

      for r=1:10

          d=rem(r,2)

                   if d==1
                   fprintf(arduino,'1');
                   else
                   fprintf(arduino,'2'); 
                   end       
      end

end

fclose(arduino); % end communication with arduino

delete(arduino);

clear('arduino');

///////// * arduino code*///////////////////////////////////////////////////////////////////

int incomingByte = 0;   // for incoming serial data

int led1 = 11;

int led2 = 12;

void setup() 

{

    Serial.begin(9600);     // opens serial port, sets data rate to 9600 bps

   pinMode(led1, OUTPUT); 

   pinMode(led2, OUTPUT); 
  }

void loop() 
{
 if (Serial.available() > 0) 

      {
                incomingByte = Serial.read();

               if(incomingByte=='1')
               {
               digitalWrite(led1, HIGH);   // turn the LED on (HIGH is the voltage level)
               delay(1000);                // wait for a second
              }  
               else if(incomingByte=='2')
               {
               digitalWrite(led2, HIGH);   // turn the LED on (HIGH is the voltage level)
               delay(1000);               // wait for a second

              }
              else
              {
                digitalWrite(led1, LOW);
                 digitalWrite(led2, LOW);    // turn the LED off by making the voltage LOW
               delay(1000);
              }
          }
  }

[Venkat damodaran Sudireddy]

the leds are not glowing even if i removed the while loop

Answer 1

[Walter Roberson]

Your code on the arduino side is counting on the fact that for serial ports, fprintf(fid, '1') means the same as fprintf(fid, '%s\n', '1') and so a newline is being queued along with the '1'. That newline is needed for the code to get to the "else" that turns off of the LEDs, since you do not turn either one off until you get a character that is not '1' or '2'

Your loop() code does not wait for serial input: it checks if there is some and does nothing if there is none. I do not know if your loop() routine will be called repeatedly by some code not shown ?