I would like to exchange data via a wireless communication using Xbee modules. I've set up a communication based on strings between the Arduino and a Matlab software. Unfortunately this kind of communication isn't enough robust and sometimes messages aren't delivered correctly. So I decided to move to the binary communication.

The Matlab software sends data correctly. I used the fwrite function as follows fwrite(xbee,hex2dec('10'));.

The problem:

I'm not able to send binary data from the Arduino to the computer.

Let's say we want to send the decimal value 17 which is 0x11 in hex if we receive 16 from Matlab.

[...]
SoftwareSerial xbee(pinRx, pinTx); 
void setup()
{
  Serial.begin(BaudRateSerial);
  xbee.begin( BaudRateXbee );
}
[...]
void loop()
{
 while(xbee.available())
  {
    getData = xbee.read();  
    if(getData == 16)
    {    
      uint8_t s = 17; 
      // First attempt
      //xbee.write(s); // doesn't work, Matlab receives number like: 32 or 117,112,116
      xbee.write(0x11);
    } 
  }
}

Then I tried to send an array of bytes and noticed that the received values were different.

byte message[] = {0x11, 0x11};

xbee.write(message, sizeof(message));

I am using in Matlab the fread function which:

reads binary data from the device connected to the serial port object, obj, and returns the data

I've also tried using XC-TU to monitor traffic on Serial port (blu values are sent from the PC, red ones are received from the Arduino) and as you can see red values are different and none of them is equivalent to 17! What am I missing?