how to properly use fprintf(obj,value) with serial ports

I use fprinf in my code to send string to the arduino UNO that i am using, problem is i have to add a while loop for it to work for example:

Required = 'Hey' arduino = (.....) %set

while( Required)
fprintf(arduino,Required)
end
fclose(arduino)
this gives an infinite loop to the COM port of the receiving arduino
so basically i removed the while loop
and the code became

Required = 'Hey'
arduino = (.....) %set
fprintf(arduino,Required)
fclose(arduino)

however it doesnt send anything at all if anyone can help in solving this, please give it all your best i searched all the mathworks forum and nothing worked Thanks in advance

Answer 1

[William Gaillard]

Arduino will reset when you open the COM port. You probably send the 'Hey' while Arduino is resetting. Give Arduino time to reset. You can add a pause to Matlab or do the following:

Try adding the following in Arduino:

above void setup()

char a = 'b';

in void setup()

Serial.println('a');          // send the char 'a' to the serial port followed by carriage return character (ASCII 13 or \r) and newline character (ASCII 10 or \n)
  while (a != 'a')              // while a does not equal 'a'
  {
    a = Serial.read();          // read the first available byte from the serial port and store as a
  }

And in Matlab after you open the COM port add the following:

a='b';
while (a ~='a') % wait until you receive an 'a' from Arduino
    a=fread(s,1,'uchar');
end
fprintf(s,'%c','a'); % send an 'a' back to Arduino