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How to sending data from matlab to arduino?

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Rayhan mo
Rayhan mo on 15 Feb 2015
Commented: Walter Roberson on 16 Jul 2021
I tried to learned some basic a sending data from matlab to arduino with a LED. i tried to turn on and off the LED if i changed some value in matlab. but the result that the LED is gived was always same. please help me to correct. my MATLAB code is
arduino=serial('COM3','BaudRate',9600); % create serial communication object on port COM3
fopen(arduino); % initiate arduino communication
answer = 0.2
fprintf(arduino,%f%,answer); % send answer to arduino
fclose(arduino); % end communication with arduino
and my arduino code is
int ledPin=13;
int matlabdata;
void setup()
{
pinMode(ledPin,OUTPUT);
Serial.begin(9600);
}
void loop()
{
if(Serial.available()>0) // if there is data to read
{
matlabdata=Serial.read(); // read data
if(matlabdata<0.2)
digitalWrite(ledPin,HIGH); // turn light on
else if(matlabdata>0.2)
digitalWrite(ledPin,LOW); // turn light off
}
}
  1 Comment
Yusof Zainol Abidin
Yusof Zainol Abidin on 3 Jan 2021
did you manage to get the answer?? im having the same problem.. please help me..

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Answers (1)

Thang Pham
Thang Pham on 16 Jul 2021
Edited: Thang Pham on 16 Jul 2021
I think the answer for your problem is: Serial.read() reads a 1-byte char-type data from the serial communication, while your sent data from MATLAB is a float-type data.
To solve this problem:
either change your sent data to char type (use fprintf(arduino, '%s', char(2)))
or change your sent data to string type and change your receive method in Arduino so that your program can read a string "0.2" and then convert it to respective float number. See: https://www.arduino.cc/reference/en/language/variables/data-types/string/functions/tofloat/ for converting string to float and https://www.arduino.cc/reference/en/language/functions/communication/serial/readstring/ for string reading.
Hope it could help you.
  1 Comment
Walter Roberson
Walter Roberson on 16 Jul 2021
fprintf(arduino,'%f\n',answer); % send answer to arduino
would send convert the numeric value in answer to character representation and send it, followed by newneline. Serial.ParseFloat() can then read the number; https://www.arduino.cc/reference/en/language/functions/communication/serial/parsefloat/

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