Java code for CRC 16 calculation

Question

Below is my hex string

String str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

and this is my CRC : A228 which is appended to the above string. I want output as A228

Polynomial used is 0xA001

Can someone provide me the code to calculate the CRC16

Below is my java code

String str="01312D0102D6010162000600000918000000000000000000000000007FFF00150010004B0100003A200207000004040055516200050E9E000200000000005852324531533156304330000001614B00541E0C07110507320000000000000000000000000500000000000000000406000030313030313033300000000000000000000046300A1D1655000186A0FFFF9EAA00000043000000000200000C000C000C000C000D000C000D000C000D000C000D000D000C000C000C000C000D000C000D000D000C000D000D000C000D000D000C000D000D000D000C000D000D000D000E000D000C000D000D000D000D000C000D000D000D000E000D000D000D000C000D000D029E029F02F102EA05300544085A07C1060F040A036404E0072F064804AA040404070510066B067205C304B302C6000D000D000D000E000D000D000E000D000E000D000D000E000D000D000E000D000E000D000E000D000E000D000D0065006300810081025102E001990082001F000E000D000E000D000E000E000D000E000D000E000E001500560062003300480068009000AF00AE00AE0214048404670560007E000E000E000E000E000E000F000E000E000E000E000E005501290168000E000E000D000E000E000E000D000E000E000E000D000E000E000D000E000E000D000E000E000D000E000E000D000E000D000E000E000E000D000E000E000D000E000E000D000E000E000D000E000E000E000D000E000E000D000E000E000D000E000E000E000D000E000E000E000D000E000E000E000D000E000E000D000E000E000E000D000E000E000E000D000E000E000E000D000E000E000E000D000E000E000E000D000E000E000D000E000E000D000E000E000E000D000E000D000E000D000E000D000E000D000E000E000D000E000D000D000D000D000D000C000D000D000E000D000D000D000D000D000D000D000E000D000D000E000D000D000E000D000D000D000D000D00E200DF00DF000F000E000D007300DF";//A228";

    byte arr[] = toByteArray(str);


        long polynomial = 0xA001;
        long CRC = 0xFFFF;

        for (byte b : arr)
        {
            CRC ^= b;
            for (int i = 8; i != 0; i--)
            {
                if ((CRC & 0x0001) != 0)
                {
                    CRC = (CRC >> 1) ^ polynomial;
                }
                else
                {
                    CRC >>= 1;
                }
            }
        }



        System.out.println(CRC);

}

I am getting output as -56289

This is not how StackOverflow works. What have you tried? Have you tried to google `crc16 java`? — OptimusCrime, Sep 12 '17 at 13:59
What about this example: https://stackoverflow.com/a/13209435/921563 — OptimusCrime, Sep 12 '17 at 14:05
First of all your `toByteArray` implementation seems to be wrong, as your code outputs -56855 when using a correct Hex decoded `str`. — Robert, Sep 12 '17 at 14:14
You certainly won’t see `A228` by just printing a long, since a long is only going to contain digits. Perhaps you meant to print it in hex using `System.out.printf("%x%n", CRC);`? — VGR, Sep 12 '17 at 14:50

Mark Adler · Accepted Answer · 2017-09-13T20:37:11.687

3

Your code is mostly fine and will produce 0xa228 for that message (with the modification below), except you have to feed it the right data and then display the resulting CRC correctly.

To feed it the right data, you first need to convert that string of hexadecimal characters into half that many binary bytes. Give that to your CRC routine.

Second, display the result in hexadecimal, not decimal.

Third, byte is signed, so do CRC ^= b & 0xff; to avoid the sign extension.

edited Sep 13 '17 at 20:37

answered Sep 12 '17 at 20:18

Mark Adler

101,978
13
118
158

I am converting the string into byte array. Also I am printing it into hex and still I am getting output as : ffffffffffff3637 – Faiz Sep 13 '17 at 05:27
Read my answer more carefully. You need to convert the _hexadecimal_ into bytes. Your 1460 characters would become 730 bytes, not 1460 bytes. – Mark Adler Sep 13 '17 at 16:24
Also I noticed that you need to fix the signed byte problem in Java. – Mark Adler Sep 13 '17 at 16:43
1

You need to provide your `toByteArray` routine to know what's really going on here. – Mark Adler Sep 13 '17 at 16:49

Java code for CRC 16 calculation

1 Answers1