crc32

[gingerologist]

根据官方资料，esp32和stm32h7的硬件crc32使用了同一个多项式。但是我实际测试发现，比如一个uint32_t类型的数组，需要把每个uint32_t数据先byteswap，然后再使用crc32_be api，两者才能算得一致的结果，而且esp32的初始值和结果还需要位反转（～），具体的，比如stm32上

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	static uint32_t chunk[5] =
	{ 0x12345678, 0x9ABCDEF0, 0x12345678, 0x00000000, 0xffffffff };

	printf("[0x00000000]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[3], 1));
	printf("[0xffffffff]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[4], 1));
	printf("[0x12345678]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[0], 1));
	printf("[0x9ABCDEF0]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[1], 1));
	printf("[0x12345678,0x9ABCDEF0]: 0x%08lx\r\n",
			HAL_CRC_Calculate(&hcrc, &chunk[0], 2));
	printf("[0x9ABCDEF0,0x12345678]: 0x%08lx\r\n",
			HAL_CRC_Calculate(&hcrc, &chunk[1], 2));

到了esp32-c3上代码要改成这样：

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    /* USER CODE BEGIN StartTestTask */
    uint32_t crc = 0xffffffff;

    // static uint32_t chunk[5] = {0x12345678, 0x9ABCDEF0, 0x12345678, 0x00000000, 0xffffffff};
    static uint32_t chunk[5] = {0x78563412, 0xF0DEBC9A, 0x78563412, 0x00000000, 0xffffffff};

    printf("=== crc test ===\r\n");

    // printf("[0x00000000]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[3], 1));
    ESP_LOGI("crc_test", "[0x00000000]: 0x%08lx\r\n", ~esp_rom_crc32_be(~crc, (const uint8_t *)&chunk[3], 4));
    ESP_LOGI("crc_test", "[0x00000000]: 0x%08lx\r\n", ~esp_rom_crc32_le(~crc, (const uint8_t *)&chunk[3], 4));

    // printf("[0xffffffff]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[4], 1));
    ESP_LOGI("crc_test", "[0xffffffff]: 0x%08lx\r\n", ~esp_rom_crc32_be(~crc, (const uint8_t *)&chunk[4], 4));
    ESP_LOGI("crc_test", "[0xffffffff]: 0x%08lx\r\n", ~esp_rom_crc32_le(~crc, (const uint8_t *)&chunk[4], 4));

    // printf("[0x12345678]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[0], 1));
    ESP_LOGI("crc_test", "[0x12345678]: 0x%08lx\r\n", ~esp_rom_crc32_be(~crc, (const uint8_t *)&chunk[0], 4));
    ESP_LOGI("crc_test", "[0x12345678]: 0x%08lx\r\n", ~esp_rom_crc32_le(~crc, (const uint8_t *)&chunk[0], 4));

    // printf("[0x9ABCDEF0]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[1], 1));
    ESP_LOGI("crc_test", "[0x9ABCDEF0]: 0x%08lx\r\n", ~esp_rom_crc32_be(~crc, (const uint8_t *)&chunk[1], 4));
    ESP_LOGI("crc_test", "[0x9ABCDEF0]: 0x%08lx\r\n", ~esp_rom_crc32_le(~crc, (const uint8_t *)&chunk[1], 4));

    // printf("[0x12345678,0x9ABCDEF0]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[0], 2));
    ESP_LOGI("crc_test", "[0x12345678,0x9ABCDEF0]: 0x%08lx\r\n", ~esp_rom_crc32_be(~crc, (const uint8_t *)&chunk[0], 8));
    ESP_LOGI("crc_test", "[0x12345678,0x9ABCDEF0]: 0x%08lx\r\n", ~esp_rom_crc32_le(~crc, (const uint8_t *)&chunk[0], 8));

    // printf("[0x9ABCDEF0,0x12345678]: 0x%08lx\r\n", HAL_CRC_Calculate(&hcrc, &chunk[1], 2));
    ESP_LOGI("crc_test", "[0x9ABCDEF0,0x12345678]: 0x%08lx\r\n", ~esp_rom_crc32_be(~crc, (const uint8_t *)&chunk[1], 8));
    ESP_LOGI("crc_test", "[0x9ABCDEF0,0x12345678]: 0x%08lx\r\n", ~esp_rom_crc32_le(~crc, (const uint8_t *)&chunk[1], 8));

其中BE版本的输出结果才和stm32一致。而如下这个软实现版本，则无论在stm32还是esp32上，结果都和stm32的crc api结果一致。

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static uint32_t SW_CRC_Calculate(uint32_t init, const uint32_t pBuffer[], uint32_t wordLength)
{
    uint32_t crc32 = init;
    for (int k = 0; k < wordLength; k++)
    {
        crc32 = crc32 ^ pBuffer[k];

        for (int i = 0; i < 32; i++)
        {
            if (crc32 & 0x80000000)
                crc32 = (crc32 << 1) ^ 0x04C11DB7;
            else
                crc32 = (crc32 << 1);
        }
    }

    return crc32;
}

请问stm32和esp32的硬件crc能不通过byteswap每个32bit word得到同样的结果吗？我需要在通讯中使用这个crc32校验数据包，不大可能考虑全部copy再byteswap的方式来实现这个校验。