stm32_crc_tool

Calculate a CRC checksum as implemented in the STM32Fx Controllers without Crypto-Hash module (e.g.: F405, F407, F427, F469, etc.). On these controllers the CRC-Module cannot be configured.

Pass the data as command line argument to this program to calculate the CRC checksum with 32 bits with the same algorithm as on the STM32Fx modules.

Outline:

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Usage

usage: stm32_crc_tool [-h] [-v] [--verbose] [-d] [-b BITS] [-p POLY] [-i VAL]
                      [-f PATH]
                      [data [data ...]]

Positional arguments:

data                  list of characters that will be treated as numbers

Optional arguments:

-h, --help            show this help message and exit
-v, --version         show program's version number and exit
--verbose             enables additional debug output
-d, --demo            display a demonstration of the stm32f4 crc algorithm
-b BITS, --bits BITS  bit length of the checksum (default is 32 bits)
-p POLY, --poly POLY  crc polynomial (default is 0x04C11DB7)
-i VAL, --init VAL    initial crc value (default is 0xFFFFFFFF)
-f PATH, --file PATH  use a file as input. The file will be parsed in 4 byte
                      chunks.

The default values equal the ones embedded in the STM hardware modules.

Example

Linux:

user@machine: $ python3 stm32_crc_tool.py -f stm32_crc_tool.py -b 8 -p 171 -i 00
0xb6

Library usage

The stm32_crc_tool can also be used as a library for other python programs. Therefore the stm32_crc_tool python file needs to be included. Then these functions are available:

embedded_crc

embedded_crc(input_data:int, poly:int=79764919, initial_crc:int=4294967295, sizeof_input:int=32) -> int

Calculates the crc for one given integer. This function represents one iteration on the embedded crc peripheral in the STM controller family. (The parameter default values equal the ones embedded in the STM hardware modules.)

rtype int

param input_data: one integer value with the specified bit length

param poly: crc polynomial to use in the algorithm

param initial_crc: crc value to start with (e.g. value from the previous iteration)

param sizeof_input: bit length of the desired crc value

return crc value of the given integer

msb

msb(val:int, bits:int=8) -> bool

returns whether the Most Significant Bit (msb) of the provided value is 1

rtype bool

param val: numeric value to check the most msb

param bits: bit length of the value

return true if the msb is a 1, false otherwise

prepare_data

prepare_data(data:str) -> [<class 'int'>]

Convert a string into a list of integers. (Uses utf-8 encoding on most machines.)

rtype [int]

param data: string to convert

return list of the int representations of the chars from the string

process_file

process_file(filename:str, poly:int=79764919, initial_crc:int=4294967295, sizeof_input:int=32) -> int

Calculates the crc for a file, interpreted as binary data. (The parameter default values equal the ones embedded in the STM hardware modules.)

rtype int

param filename: path to the file

param poly: crc polynomial to use in the algorithm

param initial_crc: crc value to start with

param sizeof_input: bit length of the desired crc value

return crc value of the provided file

process_queue

process_queue(data:str, poly:int=79764919, initial_crc:int=4294967295, sizeof_input:int=32) -> int

Calculates the crc for a string. (The parameter default values equal the ones embedded in the STM hardware modules.)

rtype int

param data: the crc value is calculated for this string

param poly: crc polynomial to use in the algorithm

param initial_crc: crc value to start with

param sizeof_input: bit length of the desired crc value

return crc value of the provided string

Licence

This software is provided under the MIT licence.

Future work

My personal plans for this repository:

• Improve the performance of the file crc calculation
• Add CI