【AT-START-F425 Review】No.04 CRC

韵湖葱白

【AT-START-F425 Review】No.04 CRC [Copy link]

 

## Introduction AT32F425 supports hardware CRC (CRC32). Compared with GD32F450 and STM32F4**, it has the following features: - Supports customization of initial value. - Supports input data inversion by 8, 16, 32 bits. - Supports output data inversion. These features are equivalent to the ability to customize CRC within a limited range. The following figure shows the CRC code calculation process of 0x34 and 0x00000034 described in the previous article, for reference by students who want to learn.  I once wrote an article explaining CRC, you can take a look: [The clearest article explaining CRC in history](https://mp.weixin.qq.com/s/DbAdErPmk6dv_nS_w6-ASQ) Online CRC website: [Online CRC](http://www.ip33.com/crc.html) --- The CRC of AT32F425 is CRC32. - The corresponding standard is: CRC32/MPEG-2 - The polynomial is: x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1, that is: 0x04C11DB7 - = Initial value is: 0xFFFFFFFF - = Input data inversion: false - = Output data inversion: false - The XOR value of the result is: 0x00000000 The equal sign above is the customizable part. ## The code interface is as follows: ``` uint32_t crc_one_word_calculate(uint32_t data); uint32_t crc_block_calculate(uint32_t *pbuffer, uint32_t length); ``` Note: **After each crc calculation, you need to call `crc_data_reset` to reset the register, otherwise it will use the previous value as the initial value. ** The test process is relatively simple: ``` static void crc_test(void) { #ifdef CRC_TEST uint32_t data = 0xabcd1234; #if defined(GD32) || defined(STM32) uint32_t crc_data = crc_single_data_calculate(data); crc_data_register_reset(); #endif #if defined(GD32M0) uint3 2_t crc_data[3]; crc_data[0] = crc_single_data_calculate(data, INPUT_FORMAT_WORD); crc_data_register_reset(); crc_data[1] = crc_single_data_calculate(data, INPUT_FORMAT_HALFWORD); crc_data_register_reset(); crc_data[2] = crc_single_data_calculate(data, INPUT_FORMAT_BYTE); crc_data_register_reset(); #endif #if defined(AT32) // crc_reverse_output_data_set(CRC_REVERSE_OUTPUT_DATA); // crc_reverse_input_data_set(CRC_REVERSE_INPUT_BY_BYTE); // crc_init_data_set(0); int32_t crc_data = crc_one_word_calculate(data); crc_data_reset(); #endif #if defined(STM32) printf("STM32: crc32 of 0x%X = 0x%X\r\n", data, crc_data); #endif #if defined(GD32) printf("GD32: crc32 of 0x%X = 0x%X\r\ n", data, crc_data); #endif #if defined(GD32M0) printf("GD32: crc32 of 0x%X = [32]0x%X [16]0x%X [8]0x%X\r\n", data, crc_data[0], crc_data[1], crc_data[2]); #endif #if defined(AT32) printf("AT32: crc32 of 0x%X = 0x%X\r\n", data, crc_data); #endif #endif } ``` CRC calculation results in different cases (input value 0xABCD1234): Configuration | CRC --- | --- CRC-MPEG2 (default) | 0xF7018A40 Input data (BYTE) inverted | 0x49FC6721 Output data inverted | 0x25180EF Initial value 0x00000000 | 0x3005573B Initial value 0xF0F0F0F0 | 0x9C6F4F19 ## The test result is printed once every 1 second.  

Jacktang

This CRC (cyclic redundancy check) online calculation is quite convenient. How did you find it? Good