How to parse bluetooth raw data

Question

I am getting a Bluetooth device raw data from my gateway and want to parse it to extract some information but it is not showing properly. Actually, the device manufacturer shared a document where it mentioned that battery level info can be found at offset 13 with a length of 1 but understand how to decode this byte to get battery level. Here is my code with the parse method which hardcoded raw data as a string(0201060303AAFE0C16AAFE10E8016D696E657700):

   public static byte[] hexStringToByteArray(String s) {
        int len = s.length();
        byte[] b = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            b[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character
                    .digit(s.charAt(i + 1), 16));
        }
        return b;
    }
    
    
   private void parse() {
        String s = "0201060303AAFE0C16AAFE10E8016D696E657700";
        byte[] adv = hexStringToByteArray(s);

        if ((0x03 & adv[4]) == 0x03) {
            System.out.println("info frame");
           System.out.println("battery:" + new String(new byte[] {advData[13]}));

        }
    }

Here is the device manufacturer document:

Answer 1

Most likely, you are trying to decode the wrong BLE advertisement. Decoding your example creates the following data.

The raw data: 02 01 06 03 03 AA FE 0C 16 AA FE 10 E8 01 6D 69 6E 65 77 00

leads to the following BLE Advertising Data Types:

Raw data	Bluetooth LE Advertising Data Type
02 01 06	Flags
03 03 AA FE	Complete List of 16bit Service Class UUIDs 0xFEAA (Google LLC, Eddystone Protocol)
0C 16 AA FE 10 E8 01 6D 69 6E 65 77 00	Service Data 16bit UUID 0xFEAA, Eddystone Protocol

Decoding the Eddystone data, see [1]:

Raw data	Eddystone frame encoding
10	URL
E8	TX Power: -24 dBm
01	URL Scheme Prefix: https://www.
6D 69 6E 65 77 00	Eddystone-URL HTTP URL encoding: minew.com/

resulting URL: https://www.minew.com/

[1] https://github.com/google/eddystone/blob/master/protocol-specification.md