Getting weird data from Arduino to Android via Bluetooth

Question

I want to receive simple data from arduino with bluetooth module attached. I am recieving data, everything works fine, but i cant read it well. Here is arduino code:

char incomingByte;

void setup() {
    Serial.begin(9600);

}

void loop() {
  Serial.println(2);
  delay(1000);

}

Here is Android code for reading data from InputStream (BufferedInputStream):

mInStream = socket.getInputStream()

public void run() {
    BufferedReader r = new BufferedReader(new InputStreamReader(mmInStream));

    while (true) {
        try {
            int a = r.read();
            Log.d(TAG, Integer.toString(a));

        } catch (IOException e) {
            break;
        }
    }
}

Here is problem: When Arduino sends number 1, Android should receive it through Buffered Input Reader as decimal value for 1 and it is equal to 49. But i get 2 additional lines in Log, always same values: 10 and 13. How to avoid reading/receiving this? Here is Logcat output for number 1 sent from Arduino:

TAG: 49
TAG: 13
TAG: 10

Whats wrong? Why does Android app receive last two lines?

score 1 · Accepted Answer · answered Jan 05 '18 at 17:11

1

This is what println() does according to Arduino's Documentation :

Prints data to the serial port as human-readable ASCII text followed by a carriage return character (ASCII 13, or '\r') and a newline character (ASCII 10, or '\n').

Use Serial.print() instead.

answered Jan 05 '18 at 17:11

Omar Aflak

2,918
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Thanks, I haven't seen in before. – masan Jan 06 '18 at 11:47

score 0 · Answer 2 · edited Jan 05 '18 at 20:27

I will focus on two aspects of the above program.

In the above program, two extra tags that are been printed are ASCII Values - 10 for "line feed" and 13 for "carriage return".
The Serial.println adds a "carriage return" and "line feed character" to the end of what is being printed. Serial.print doesn't add anything.
So you can use Serial.print.

Also, for the part of reading from InputStream, you can also prefer the following code: link

BufferedReader r = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder total = new StringBuilder();
String line;
while ((line = r.readLine()) != null) {
    total.append(line).append('\n');
}

Getting weird data from Arduino to Android via Bluetooth

2 Answers2