crc16 | Implements the 16-bit cyclic redundancy check or CRC-16

I have some technical documentation and try to replicate the given CRC algorithm in python. However I don't get the correct results. How do I have to tweak my algo to match the docs?

This is the documentation:

And this is my code:

I have some trouble implementing a CRC16 for can message, I followed the instructions given by this website https://barrgroup.com/embedded-systems/how-to/crc-calculation-c-code and http://www.sunshine2k.de/articles/coding/crc/understanding_crc.html#ch5, plus other implention I have seen in here ( for example Function to Calculate a CRC16 Checksum).

I don't understand how it is processed. My message here is in form of bytes, for example char message[4] = {0x12, 0x34, 0x56, 0x78}. When I go through the first loop I just take the first byte, shift it by 8 and calculate the remainder with a POLYNOME of 16 bits. That means we have 0x1200 and we go through the second loop with it, which mean I do a XOR with the POLYNOME that I store in the remainder but I don't quite understand why this works, especially when I look at this code, the 2nd, 3rd and 4th bytesof my message which should get XORed by the 8 first bits of the POLYNOME at some points aren't going through it at all. According to the wikipedia explanation https://en.wikipedia.org/wiki/Cyclic_redundancy_check the polynome goes through the whole message at once and not byte by byte. I don't know how that translates to doing the CRC of 0x12345678 byte by byte.

I am trying to calculate CRC for the first time. I have read a few pages that explain what is crc and how to calculate. Mainly this : https://www.fatalerrors.org/a/implementation-of-crc-checksum-c-crc16-as-an-example.html

I have a code that calculates CRC16

Please excuse me if the question will be simple, I'm kinda new with CRC.

I've got cpp CRC16 func with defined crc table and I want exactly the same results in python. I used some libraries, but all of them gave me different results. The reason is probably with diference in crc tables, but all the algorithms that I found don't have defined tables that I can swap with mine.

Original func:

I am in need of a highly optimized CRC8 algorithm. My goal is to develop a Slice-by-4 solution as known from CRC16 / CRC32. I want to keep the code as close to the solution which I am using for CRC16 posted below.

Functions to generate the CRC LookUp-Table:

I'm struggling with an old radiation sensor and his communication protocol.
The sensor is event driven, the master starts the communication with a data transmission or a data request.
Each data telegram uses a CRC16 to check only the variable data block and a CRC8 to check all the telegram.

My main problem is the crc16, According to the datasheet the poly used to check the data block is:
CRC16 = X^14 + X^12 + X^5 + 1 --> 0x5021 ??

I captured some data with a valid CRC16 and tried to replicate the expected value in order to send my own data transmission, but I can't get the same value.
I'm using the sunshine CRC calculator trying any possible combination with that poly. I also try CRC Reveng but no results.

Here are a few data with the correct CRC16:.

I need to calculate a CRC16 for hex codes like this one: 08010000016B40D8EA30010000000000000000000000000000000105021503010101425E0F01F10000601A014E000000000000000001

The expected result for the above hex String is 0000C7CF ( 51151 )

I have this working JavaScript implementation for that, which I am trying to translate to Java:

I have created a minimal stereo FLAC file according to the specifications here. It is a single block of 8192 samples of 0 encoded as a constant:

Below code is from crc32 function reference in PHP website for CRC16-CCITT calculation. This works for ASCII input data. How can I make it work for HEX input data? What do I need to change? Thank you for your help.