ESP8266 Community Forum

Environment: FreeRTOS SDK
In Memory Map, I saw a 32k user-defined storage at 0x40002000 mapped to flash, but when I use memcpy((char*)(0x40002000), something) esp8266 threw an Exception 29.
I looked up xtensa document, it means StoreProhibitedCause. And I tried spi_flash_write(0x3C000, buffer, size), the same exception was threw.
The problem is how can i store my data into flash, and what is its size?

Sorry for my poor English, hope you can understand the text.

You may look at example code in at_baseCmd.c from at_v0.20_on_SDKv0.9.3

code for load some parameters:


code for save parameters:


some definitions:


From here: https://github.com/esp8266/esp8266-wiki/wiki/Memory-Map
we may see the following about SPI Flash memory:

This area is readable as data with aligned 4-byte reads.

As you may see, esp_platform_sec_flag_param structure is 4-byte aligned.
Is the buffer in your code spi_flash_write(0x3C000, buffer, size) 4-byte aligned?

rekod wrote:You may look at example code in at_baseCmd.c from at_v0.20_on_SDKv0.9.3

code for load some parameters:

Code: Select all/******************************************************************************
 * FunctionName : user_esp_platform_load_param
 * Description  : load parameter from flash, toggle use two sector by flag value.
 * Parameters   : param--the parame point which write the flash
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_esp_platform_load_param(void *param, uint16 len)
{
    struct esp_platform_sec_flag_param flag;

    spi_flash_read((ESP_PARAM_START_SEC + ESP_PARAM_FLAG) * SPI_FLASH_SEC_SIZE,
                   (uint32 *)&flag, sizeof(struct esp_platform_sec_flag_param));

    if (flag.flag == 0) {
        spi_flash_read((ESP_PARAM_START_SEC + ESP_PARAM_SAVE_0) * SPI_FLASH_SEC_SIZE,
                       (uint32 *)param, len);
    } else {
        spi_flash_read((ESP_PARAM_START_SEC + ESP_PARAM_SAVE_1) * SPI_FLASH_SEC_SIZE,
                       (uint32 *)param, len);
    }
}

code for save parameters:

Code: Select all/******************************************************************************
 * FunctionName : user_esp_platform_save_param
 * Description  : toggle save param to two sector by flag value,
 *              : protect write and erase data while power off.
 * Parameters   : param -- the parame point which write the flash
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_esp_platform_save_param(void *param, uint16 len)
{
    struct esp_platform_sec_flag_param flag;

    spi_flash_read((ESP_PARAM_START_SEC + ESP_PARAM_FLAG) * SPI_FLASH_SEC_SIZE,
                       (uint32 *)&flag, sizeof(struct esp_platform_sec_flag_param));

    if (flag.flag == 0) {
        spi_flash_erase_sector(ESP_PARAM_START_SEC + ESP_PARAM_SAVE_1);
        spi_flash_write((ESP_PARAM_START_SEC + ESP_PARAM_SAVE_1) * SPI_FLASH_SEC_SIZE,
                        (uint32 *)param, len);
        flag.flag = 1;
        spi_flash_erase_sector(ESP_PARAM_START_SEC + ESP_PARAM_FLAG);
        spi_flash_write((ESP_PARAM_START_SEC + ESP_PARAM_FLAG) * SPI_FLASH_SEC_SIZE,
                        (uint32 *)&flag, sizeof(struct esp_platform_sec_flag_param));
    } else {
        spi_flash_erase_sector(ESP_PARAM_START_SEC + ESP_PARAM_SAVE_0);
        spi_flash_write((ESP_PARAM_START_SEC + ESP_PARAM_SAVE_0) * SPI_FLASH_SEC_SIZE,
                        (uint32 *)param, len);
        flag.flag = 0;
        spi_flash_erase_sector(ESP_PARAM_START_SEC + ESP_PARAM_FLAG);
        spi_flash_write((ESP_PARAM_START_SEC + ESP_PARAM_FLAG) * SPI_FLASH_SEC_SIZE,
                        (uint32 *)&flag, sizeof(struct esp_platform_sec_flag_param));
    }
}

some definitions:

Code: Select all#define ESP_PARAM_START_SEC   0x3C

#define ESP_PARAM_SAVE_0    1
#define ESP_PARAM_SAVE_1    2
#define ESP_PARAM_FLAG      3
struct esp_platform_sec_flag_param {
    uint8 flag;
    uint8 pad[3];
};


From here: https://github.com/esp8266/esp8266-wiki/wiki/Memory-Map
we may see the following about SPI Flash memory:

This area is readable as data with aligned 4-byte reads.

As you may see, esp_platform_sec_flag_param structure is 4-byte aligned.
Is the buffer in your code spi_flash_write(0x3C000, buffer, size) 4-byte aligned?

yes, its size is 64 bytes.
spi_flash_write worked in 0.9.3 SDK but does not work in RTOS SDK, I tried erase , it works fine, but write function always threw a Exception 29
Fatal exception (29):
epc1=0x4000bf1b
epc2=0x00000000
epc3=0x40243069
epcvaddr=0x00000000
depc=0x00000000

I tried and tried all day, but nothing useful got.