Send multiple character string to arduino

Hi all,

I want to establish a communication between Matlab and my Arduino. Therefore, I want to send one string that contains ~500 characters. To verify my code, I want to send a string that contains 5 characters. If the transmitting was succesful, a LED attached to my arduino will turn on. I use this arduino code.

if true
int LEDPin = 2;
int msg_length = 0;
char userInput[500];
int data = 0;
char tmp;
void setup()
{
Serial.begin(9600);
pinMode(LEDPin, OUTPUT);
}
void loop()
{
delay(500);  
if ( data == 0 ) {
  Serial.println('a'); 
if (Serial.available()) {
  msg_length = Serial.available();
  if ( msg_length == 5  ) {
    tmp = Serial.read();
    if ( tmp == 'S' ) {
      userInput[0] = tmp;
      for (int i = 1; i <= msg_length; i++) {
        tmp = Serial.read();
        userInput[i] = char(tmp);
      }
      data = 1;
      digitalWrite(LEDPin, HIGH);
      userInput[499] = {'\r'};
    }
  }
}
}}
end

And this code in Matlab.

if true
  function arduinoCom
instrreset;
clear all;
arduino=serial('COM5','BaudRate',9600); % create serial communication object on port COM4
fopen(arduino); % initiate arduino communication 
  fprintf(arduino, '%c', 'S1234'); % 'S1234' is what i want to transmit
fclose(arduino); % end communication with arduino
end

end

If I use the serial monitor from Arduino IDE and I type in my string 'S1234', it works and the LED turns on. However, when I use the matlab method, it doesn't.

I am not familiar with the communication via serial ports, so pls feel free to critisize me.

Thanks a lot!

Answer 1

[Tristan Yang]

Hi Dennis,

In order to write to a string to serial port in MATLAB, please use the '%s' as the format instead of '%c': >> fprintf(arduino, '%s', 'S1234');

Please refer to the documentation below for more information on 'fprintf' function for serial communication: https://www.mathworks.com/help/matlab/ref/serial.fprintf.html