Espressif ESP32-S2 User Manual

Chapter 2. API Reference
Overriding Default Chip Drivers During the SPI Flash driver’s initialization (i.e., esp_flash_init()),
there is a chip detection step during which the driver will iterate through a Default Chip Driver List and determine
which chip driver can properly support the currently connected flash chip. The Default Chip Drivers are provided by
the IDF, thus are updated in together with each IDF version. However IDF also allows users to customize their own
chip drivers.
Users should note the following when customizing chip drivers:
1. You may need to rely on some non-public IDF functions, which have slight possibility to change between IDF
versions. On the one hand, these changes may be useful bug fixes for your driver, on the other hand, they may
also be breaking changes (i.e., breaks your code).
2. Some IDF bug fixes to other chip drivers will not be automatically applied to your own custom chip drivers.
3. If the protection of flash is not handled properly, there may be some random reliability issues.
4. If you update to a newer IDF version that has support for more chips, you will have to manually add those new
chip drivers into your custom chip driver list. Otherwise the driver will only search for the drivers in custom
list you provided.
Steps For Creating Custom Chip Drivers and Overriding the IDF Default Driver List
1. Enable the CONFIG_SPI_FLASH_OVERRIDE_CHIP_DRIVER_LIST config option. This will prevent compila-
tion and linking of the Default Chip Driver List (default_registered_chips) provided by IDF. Instead, the linker
will search for the structure of the same name (default_registered_chips) that must be provided by the user.
2. Add a new component in your project, e.g. custom_chip_driver.
3. Copy the necessary chip driver files from the spi_flash component in IDF. This may include:
• spi_flash_chip_drivers.c (to provide the default_registered_chips structure)
• Any of the spi_flash_chip_*.c files that matches your own flash model best
• CMakeLists.txt and linker.lf files
Modify the files above properly.
Note:
• When writing your own flash chip driver, you can set your flash chip capabilities through
spi_flash_chip_***(vendor)_get_caps and points the function pointer get_chip_caps for protection to
the spi_flash_chip_***_get_caps function. The steps are as follows.
1. Please check whether your flash chip have the capabilities listed in spi_flash_caps_t by check-
ing the flash datasheet.
2. Write a function named spi_flash_chip_***(vendor)_get_caps. Take the example below as a
reference. (if the flash support suspend and read unique id).
3. Points the the pointer get_chip_caps (in spi_flash_chip_t) to the function mentioned above.
spi_flash_caps_t spi_flash_chip_***(vendor)_get_caps(esp_flash_t *chip)
{
spi_flash_caps_t caps_flags = 0;
// 32-bit-address flash is not supported
flash-suspend is supported
caps_flags |= SPI_FLAHS_CHIP_CAP_SUSPEND;
// flash read unique id.
caps_flags |= SPI_FLASH_CHIP_CAP_UNIQUE_ID;
return caps_flags;
}
const spi_flash_chip_t esp_flash_chip_eon = {
// Other function pointers
.get_chip_caps = spi_flash_chip_eon_get_caps,
};
• You also can see how to implement this in the example storage/custom_flash_driver.
4. Add linking dependency from spi_flash component to the new custom_chip_driver component, by adding the
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Espressif ESP32-S2 Specifications

General

Brand	Espressif
Model	ESP32-S2
Category	Single board computers
Language	English