How to read data from arduino bluetooth?

Question

kintali narendra 2016-9-21

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/303966-how-to-read-data-from-arduino-bluetooth

评论： Walter Roberson 2016-9-23

I am successful in sending data from matlab to arduino via Bluetooth, but I am unable to read the data sent by Arduino-bluetooth(JY-MCU).

% serial communication between matlab and bluetooth     
delete(instrfind);
b = Bluetooth('BTslave',1);
fopen(b); %write and read function
fwrite(b,'K');
A = fread(b,5)
fclose(b);
clear('b');

I am able to read 5 values but they are just random values not the right values.

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Answer 1

Walter Roberson 2016-9-21

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https://ww2.mathworks.cn/matlabcentral/answers/303966-how-to-read-data-from-arduino-bluetooth#answer_235597

Watch out for the default on fread() being 'double' . If the bluetooth device is sending data in some other datatype you need to adjust your fread() to know that.

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kintali narendra 2016-9-23

编辑：kintali narendra 2016-9-23

在 MATLAB Online 中打开

Hi Walter, I tried all clues which u have given, but still there is no success. here is my Arduino code.

 char val; // variable to receive data from the serial port
int ledpin = 8; // LED pin1
int ledpin2 = 9; // LED pin2
void setup() {
  pinMode(ledpin, OUTPUT);  // Onboard LED as OUTPUT
  pinMode(ledpin2, OUTPUT);
  Serial.begin(9600);       // start serial communication at 9600bps
}
{
void loop() {
  if( Serial.available() )       // if data is available to read
  { val = Serial.read();  }       // read it and store it in 'val'
  if( val == 'K' )               // if 'K' was received
  {
    digitalWrite(ledpin, HIGH);  // turn ON the LED
    digitalWrite(ledpin2, LOW);
    int potvalue = analogRead(A5);
    Serial.print(potvalue);
  } else { 
    digitalWrite(ledpin, LOW);   // otherwise turn it OFF
    digitalWrite(ledpin2, HIGH);
    int potvalue = analogRead(A5);
    Serial.println(potvalue);
  }
 delay(1000);                    // wait 100ms for next reading
}

I even tried reading values of the sensor from Com15 where I can see sensor values in Arduino-IDE but it didn't work. It gives an error "com port is unable to open".

kintali narendra 2016-9-23

编辑：kintali narendra 2016-9-23

Hi Walter, sorry, I didnt see the mistake in the comment section. It worked perfectly with fscanf() thanku. Can u say why it didn't work for fread() and how to make matlab to read the value continuously.

Walter Roberson 2016-9-23

Earlier I indicated that the default for fread was double. That was incorrect: the default is uint8=>double . Each character of the printable values was being interpreted as a separate value, but you needed a group of printable values to be read together as a single value.

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