# Over The Air Updates (OTA)

[中文]

## OTA Process Overview

The OTA update mechanism allows a device to update itself based on data received while the normal firmware is running (for example, over Wi-Fi, Bluetooth or Ethernet).

The following modes support OTA updates for certain partitions:

- Safe update mode. The update process for certain partitions is designed to be resilient, ensuring that even if the power is cut off during the update, the chip will remain operational and capable of booting the current application. The following partitions support this mode:

  - Application. OTA requires configuring the Partition Tables of the device with at least two OTA app slot partitions (i.e., `ota_0` and `ota_1`) and an OTA Data Partition. The OTA operation functions write a new app firmware image to whichever OTA app slot that is currently not selected for booting. Once the image is verified, the OTA Data partition is updated to specify that this image should be used for the next boot.

- Unsafe update mode. The update process is vulnerable, meaning that a power interruption during the update can cause issues that prevent the current application from loading, potentially leading to an unrecoverable state. The temporary partition receives the new image, and once it is fully downloaded, the image is copied to the final destination partition. If an interruption occurs during this final copying process, it can lead to issues. The following partitions support this mode:

  - Bootloader.

  - Partition table.

  - Other data partitions like NVS, FAT, etc.

## OTA Data Partition

An OTA data partition (type `data`, subtype `ota`) must be included in the Partition Tables of any project which uses the OTA functions.

For factory boot settings, the OTA data partition should contain no data (all bytes erased to 0xFF). In this case, the ESP-IDF second stage bootloader boots the factory app if it is present in the partition table. If no factory app is included in the partition table, the first available OTA slot (usually `ota_0`) is booted.

After the first OTA update, the OTA data partition is updated to specify which OTA app slot partition should be booted next.

The OTA data partition is two flash sectors (0x2000 bytes) in size, to prevent problems if there is a power failure while it is being written. Sectors are independently erased and written with matching data, and if they disagree a counter field is used to determine which sector was written more recently.

## App Rollback

The main purpose of the application rollback is to keep the device working after the update. This feature allows you to roll back to the previous working application in case a new application has critical errors. When the rollback process is enabled and an OTA update provides a new version of the app, one of three things can happen:

- The application works fine, `esp_ota_mark_app_valid_cancel_rollback()` marks the running application with the state `ESP_OTA_IMG_VALID`. There are no restrictions on booting this application.

- The application has critical errors and further work is not possible, a rollback to the previous application is required, `esp_ota_mark_app_invalid_rollback_and_reboot()` marks the running application with the state `ESP_OTA_IMG_INVALID` and reset. This application will not be selected by the bootloader for boot and will boot the previously working application.

- If the CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is set, and a reset occurs without calling either function then the application is rolled back.

The following code serves detect the initial boot for an application after the OTA update. Upon the first boot, the application checks its state and performs diagnostics. If the diagnostics are successful, the application should call `esp_ota_mark_app_valid_cancel_rollback()` to confirm the operability of the application. If the diagnostics fail, the application should call `esp_ota_mark_app_invalid_rollback_and_reboot()` to roll back to the previous working application.

If the application is not able to boot or execute this code due to an abort/reboot/power loss error, the bootloader marks this application as `ESP_OTA_IMG_INVALID` in the next booting attempt and rolls back to the previous working application.

    const esp_partition_t *running = esp_ota_get_running_partition();
    esp_ota_img_states_t ota_state;
    if (esp_ota_get_state_partition(running, &ota_state) == ESP_OK) {
        if (ota_state == ESP_OTA_IMG_PENDING_VERIFY) {
            // run diagnostic function ...
            bool diagnostic_is_ok = diagnostic();
            if (diagnostic_is_ok) {
                ESP_LOGI(TAG, "Diagnostics completed successfully! Continuing execution ...");
                esp_ota_mark_app_valid_cancel_rollback();
            } else {
                ESP_LOGE(TAG, "Diagnostics failed! Start rollback to the previous version ...");
                esp_ota_mark_app_invalid_rollback_and_reboot();
            }
        }
    }

For the example incorporating the above code snippet, see the system/ota/native_ota_example example.

Note

The state is not written to the binary image of the application but rather to the `otadata` partition. The partition contains a `ota_seq` counter, which is a pointer to the slot (`ota_0`, `ota_1`, ...) from which the application will be selected for boot.

### App OTA State

States control the process of selecting a boot app:

States | Restriction of selecting a boot app in bootloader
--- | ---
ESP_OTA_IMG_VALID | None restriction. Will be selected.
ESP_OTA_IMG_UNDEFINED | None restriction. Will be selected.
ESP_OTA_IMG_INVALID | Will not be selected.
ESP_OTA_IMG_ABORTED | Will not be selected.
ESP_OTA_IMG_NEW | If CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is set it will be selected only once. In bootloader the state immediately changes to `ESP_OTA_IMG_PENDING_VERIFY`.
ESP_OTA_IMG_PENDING_VERIFY | If CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is set it will not be selected, and the state will change to `ESP_OTA_IMG_ABORTED`.

If CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is not enabled (by default), then the use of the following functions `esp_ota_mark_app_valid_cancel_rollback()` and `esp_ota_mark_app_invalid_rollback_and_reboot()` are optional, and `ESP_OTA_IMG_NEW` and `ESP_OTA_IMG_PENDING_VERIFY` states are not used.

An option in Kconfig CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE allows you to track the first boot of a new application. In this case, the application must confirm its operability by calling `esp_ota_mark_app_valid_cancel_rollback()` function, otherwise the application will be rolled back upon reboot. It allows you to control the operability of the application during the boot phase. Thus, a new application has only one attempt to boot successfully.

### Rollback Process

The description of the rollback process when CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is enabled:

- The new application is successfully downloaded and `esp_ota_set_boot_partition()` function makes this partition bootable and sets the state `ESP_OTA_IMG_NEW`. This state means that the application is new and should be monitored for its first boot.

- Reboot `esp_restart()`.

- The bootloader checks for the `ESP_OTA_IMG_PENDING_VERIFY` state if it is set, then it will be written to `ESP_OTA_IMG_ABORTED`.

- The bootloader selects a new application to boot so that the state is not set as `ESP_OTA_IMG_INVALID` or `ESP_OTA_IMG_ABORTED`.

- The bootloader checks the selected application for `ESP_OTA_IMG_NEW` state if it is set, then it will be written to `ESP_OTA_IMG_PENDING_VERIFY`. This state means that the application requires confirmation of its operability, if this does not happen and a reboot occurs, this state will be overwritten to `ESP_OTA_IMG_ABORTED` (see above) and this application will no longer be able to start, i.e., there will be a rollback to the previous working application.

- A new application has started and should make a self-test.

- If the self-test has completed successfully, then you must call the function `esp_ota_mark_app_valid_cancel_rollback()` because the application is awaiting confirmation of operability (`ESP_OTA_IMG_PENDING_VERIFY` state).

- If the self-test fails, then call `esp_ota_mark_app_invalid_rollback_and_reboot()` function to roll back to the previous working application, while the invalid application is set `ESP_OTA_IMG_INVALID` state.

- If the application has not been confirmed, the state remains `ESP_OTA_IMG_PENDING_VERIFY`, and the next boot it will be changed to `ESP_OTA_IMG_ABORTED`, which prevents re-boot of this application. There will be a rollback to the previous working application.

### Unexpected Reset

If a power loss or an unexpected crash occurs at the time of the first boot of a new application, it will roll back the application.

Recommendation: Perform the self-test procedure as quickly as possible, to prevent rollback due to power loss.

Only `OTA` partitions can be rolled back. Factory partition is not rolled back.

### Booting Invalid/aborted Apps

Booting an application which was previously set to `ESP_OTA_IMG_INVALID` or `ESP_OTA_IMG_ABORTED` is possible:

- Get the last invalid application partition `esp_ota_get_last_invalid_partition()`.

- Pass the received partition to `esp_ota_set_boot_partition()`, this will update the `otadata`.

- Restart `esp_restart()`. The bootloader will boot the specified application.

To determine if self-tests should be run during startup of an application, call the `esp_ota_get_state_partition()` function. If result is `ESP_OTA_IMG_PENDING_VERIFY` then self-testing and subsequent confirmation of operability is required.

### Where the States Are Set

A brief description of where the states are set:

- `ESP_OTA_IMG_VALID` state is set by `esp_ota_mark_app_valid_cancel_rollback()` function.

- `ESP_OTA_IMG_UNDEFINED` state is set by `esp_ota_set_boot_partition()` function if CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is not enabled.

- `ESP_OTA_IMG_NEW` state is set by `esp_ota_set_boot_partition()` function if CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is enabled.

- `ESP_OTA_IMG_INVALID` state is set by function `esp_ota_mark_app_invalid_rollback()` or `esp_ota_mark_app_invalid_rollback_and_reboot()`.

- `ESP_OTA_IMG_ABORTED` state is set if there was no confirmation of the application operability and occurs reboots (if CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is enabled).

- `ESP_OTA_IMG_PENDING_VERIFY` state is set in a bootloader if CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE option is enabled and selected app has `ESP_OTA_IMG_NEW` state.

## Anti-rollback

Anti-rollback prevents rollback to application with security version lower than one programmed in eFuse of chip.

This function works if set CONFIG_BOOTLOADER_APP_ANTI_ROLLBACK option. In the bootloader, when selecting a bootable application, an additional security version check is added which is on the chip and in the application image. The version in the bootable firmware must be greater than or equal to the version in the chip.

CONFIG_BOOTLOADER_APP_ANTI_ROLLBACK and CONFIG_BOOTLOADER_APP_ROLLBACK_ENABLE options are used together. In this case, rollback is possible only on the security version which is equal or higher than the version in the chip.

### A Typical Anti-rollback Scheme Is

- New firmware released with the elimination of vulnerabilities with the previous version of security.

- After the developer makes sure that this firmware is working. He can increase the security version and release a new firmware.

- Download new application.

- To make it bootable, run the function `esp_ota_set_boot_partition()`. If the security version of the new application is smaller than the version in the chip, the new application will be erased. Update to new firmware is not possible.

- Reboot.

- In the bootloader, an application with a security version greater than or equal to the version in the chip will be selected. If otadata is in the initial state, and one firmware was loaded via a serial channel, whose secure version is higher than the chip, then the secure version of efuse will be immediately updated in the bootloader.

- New application booted. Then the application should perform diagnostics of the operation and if it is completed successfully, you should call `esp_ota_mark_app_valid_cancel_rollback()` function to mark the running application with the `ESP_OTA_IMG_VALID` state and update the secure version on chip. Note that if the `esp_ota_mark_app_invalid_rollback()` or `esp_ota_mark_app_invalid_rollback_with_reboot()` function is called a rollback may not happen as the device may not have any bootable apps. It will then return `ESP_ERR_OTA_ROLLBACK_FAILED` error and stay in the `ESP_OTA_IMG_PENDING_VERIFY` state.

- The next update of app is possible if a running app is in the `ESP_OTA_IMG_VALID` state.

Recommendation:

If you want to avoid the download/erase overhead in case of the app from the server has security version lower than the running app, you have to get `new_app_info.secure_version` from the first package of an image and compare it with the secure version of efuse. Use `esp_efuse_check_secure_version(new_app_info.secure_version)` function if it is true then continue downloading otherwise abort.

    ....
    bool image_header_was_checked = false;
    while (1) {
        int data_read = esp_http_client_read(client, ota_write_data, BUFFSIZE);
        ...
        if (data_read > 0) {
            if (image_header_was_checked == false) {
                esp_app_desc_t new_app_info;
                if (data_read > sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t) + sizeof(esp_app_desc_t)) {
                    // check current version with downloading
                    if (esp_efuse_check_secure_version(new_app_info.secure_version) == false) {
                      ESP_LOGE(TAG, "This a new app can not be downloaded due to a secure version is lower than stored in efuse.");
                      http_cleanup(client);
                      task_fatal_error();
                    }

                    image_header_was_checked = true;

                    esp_ota_begin(update_partition, OTA_SIZE_UNKNOWN, &update_handle);
                }
            }
            esp_ota_write( update_handle, (const void *)ota_write_data, data_read);
        }
    }
    ...

Restrictions:

- The number of bits in the `secure_version` field is limited to 16 bits. This means that only 16 times you can do an anti-rollback. You can reduce the length of this efuse field using CONFIG_BOOTLOADER_APP_SEC_VER_SIZE_EFUSE_FIELD option.

- Factory and Test partitions are not supported in anti rollback scheme and hence partition table should not have partition with SubType set to `factory` or `test`.

`security_version`:

- In application image it is stored in `esp_app_desc` structure. The number is set CONFIG_BOOTLOADER_APP_SECURE_VERSION.

## Secure OTA Updates Without Secure Boot

The verification of signed OTA updates can be performed even without enabling hardware secure boot. This can be achieved by setting CONFIG_SECURE_SIGNED_APPS_NO_SECURE_BOOT and CONFIG_SECURE_SIGNED_ON_UPDATE_NO_SECURE_BOOT.

## Tuning OTA Performance

- Erasing the update partition at once instead of sequential erasing (default mechanism) while write operation might help in reducing the overall time taken for firmware upgrade. To enable this, set `esp_https_ota_config_t::bulk_flash_erase` to true in `esp_https_ota_config_t` structure. If the partition to be erased is too large, task watchdog could be triggered. It is advised to increase the watchdog timeout in such cases.

      esp_https_ota_config_t ota_config = {
          .bulk_flash_erase = true,
      }

- Tuning the `esp_https_ota_config_t::http_config::buffer_size` can also help in improving the OTA performance.

- `esp_https_ota_config_t` has a member `esp_https_ota_config_t::buffer_caps` which can be used to specify the memory type to use when allocating memory to the OTA buffer. Configuring this value to MALLOC_CAP_INTERNAL might help in improving the OTA performance when SPIRAM is enabled.

- For optimizing network performance, please refer to Improving Network Speed section in the Speed Optimization for more details.

## OTA Tool `otatool.py`

The component `app_update` provides a tool app_update/otatool.py for performing OTA partition-related operations on a target device. The following operations can be performed using the tool:

> - read contents of otadata partition (read_otadata)

> - erase otadata partition, effectively resetting device to factory app (erase_otadata)

> - switch OTA partitions (switch_ota_partition)

> - erasing OTA partition (erase_ota_partition)

> - write to OTA partition (write_ota_partition)

> - read contents of OTA partition (read_ota_partition)

The tool can either be imported and used from another Python script or invoked from shell script for users wanting to perform operation programmatically. This is facilitated by the tool's Python API and command-line interface, respectively.

### Python API

Before anything else, make sure that the `otatool` module is imported.

    import sys
    import os

    idf_path = os.environ["IDF_PATH"]  # get value of IDF_PATH from environment
    otatool_dir = os.path.join(idf_path, "components", "app_update")  # otatool.py lives in $IDF_PATH/components/app_update

    sys.path.append(otatool_dir)  # this enables Python to find otatool module
    from otatool import *  # import all names inside otatool module

The starting point for using the tool's Python API to do is create an `OtatoolTarget` object:

    # Create a parttool.py target device connected on serial port /dev/ttyUSB1
    target = OtatoolTarget("/dev/ttyUSB1")

The created object can now be used to perform operations on the target device:

    # Erase otadata, resetting the device to factory app
    target.erase_otadata()

    # Erase contents of OTA app slot 0
    target.erase_ota_partition(0)

    # Switch boot partition to that of app slot 1
    target.switch_ota_partition(1)

    # Read OTA partition 'ota_3' and save contents to a file named 'ota_3.bin'
    target.read_ota_partition("ota_3", "ota_3.bin")

The OTA partition to operate on is specified using either the app slot number or the partition name.

More information on the Python API is available in the docstrings for the tool.

### Command-line Interface

The command-line interface of `otatool.py` has the following structure:

    otatool.py [command-args] [subcommand] [subcommand-args]

    - command-args - these are arguments that are needed for executing the main command (parttool.py), mostly pertaining to the target device
    - subcommand - this is the operation to be performed
    - subcommand-args - these are arguments that are specific to the chosen operation

    # Erase otadata, resetting the device to factory app
    otatool.py --port "/dev/ttyUSB1" erase_otadata

    # Erase contents of OTA app slot 0
    otatool.py --port "/dev/ttyUSB1" erase_ota_partition --slot 0

    # Switch boot partition to that of app slot 1
    otatool.py --port "/dev/ttyUSB1" switch_ota_partition --slot 1

    # Read OTA partition 'ota_3' and save contents to a file named 'ota_3.bin'
    otatool.py --port "/dev/ttyUSB1" read_ota_partition --name=ota_3 --output=ota_3.bin

More information can be obtained by specifying `--help` as argument:

    # Display possible subcommands and show main command argument descriptions
    otatool.py --help

    # Show descriptions for specific subcommand arguments
    otatool.py [subcommand] --help

## See Also

- Partition Tables

- Partitions API

- SPI Flash API

- ESP HTTPS OTA

## Application Examples

- system/ota/native_ota_example demonstrates how to use the app_update component's APIs for native over-the-air (OTA) updates on ESP32-C3. For applicable SoCs, please refer to system/ota/native_ota_example/README.md.

- system/ota/otatool demonstrates how to use the OTA tool to perform operations such as reading, writing, and erasing OTA partitions, switching boot partitions, and switching to factory partition. For more information, please refer to system/ota/otatool/README.md.

## API Reference

### Header File

- components/app_update/include/esp_ota_ops.h

- This header file can be included with:

  >     #include "esp_ota_ops.h"

- This header file is a part of the API provided by the `app_update` component. To declare that your component depends on `app_update`, add the following to your CMakeLists.txt:

  >     REQUIRES app_update

  > or

  >     PRIV_REQUIRES app_update

### Functions

const esp_app_desc_t *esp_ota_get_app_description(void)

  Return esp_app_desc structure. This structure includes app version.

  Return description for running app.

  Note

  This API is present for backward compatibility reasons. Alternative function with the same functionality is `esp_app_get_description`

  Returns:

    Pointer to esp_app_desc structure.

int esp_ota_get_app_elf_sha256(char *dst, size_t size)

  Fill the provided buffer with SHA256 of the ELF file, formatted as hexadecimal, null-terminated. If the buffer size is not sufficient to fit the entire SHA256 in hex plus a null terminator, the largest possible number of bytes will be written followed by a null.

  Note

  This API is present for backward compatibility reasons. Alternative function with the same functionality is `esp_app_get_elf_sha256`

  Parameters:

    - dst -- Destination buffer

    - size -- Size of the buffer

  Returns:

    Number of bytes written to dst (including null terminator)

esp_err_t esp_ota_begin(const esp_partition_t *partition, size_t image_size, esp_ota_handle_t *out_handle)

  Commence an OTA update writing to the specified partition.

  The specified partition is erased to the specified image size.

  If image size is not yet known, pass OTA_SIZE_UNKNOWN which will cause the entire partition to be erased.

  On success, this function allocates memory that remains in use until esp_ota_end() is called with the returned handle.

  Note: If the rollback option is enabled and the running application has the ESP_OTA_IMG_PENDING_VERIFY state then it will lead to the ESP_ERR_OTA_ROLLBACK_INVALID_STATE error. Confirm the running app before to run download a new app, use esp_ota_mark_app_valid_cancel_rollback() function for it (this should be done as early as possible when you first download a new application).

  Note: Rollback is applicable only for app type partitions. Note: For Rollback - The OTA data slot corresponding to the last boot application partition will be invalidated.

  Parameters:

    - partition -- Pointer to info for partition which will receive the OTA update. Required. This is considered as the staging partition (where OTA is downloaded), be default this also considered as the final partition which supposed to be updated. The final partition can be overwritten using esp_ota_set_final_partition() after calling esp_ota_begin() to relocate contents to the final destination partition.

    - image_size -- Size of new OTA app image. Partition will be erased in order to receive this size of image. If 0 or OTA_SIZE_UNKNOWN, the entire partition is erased.

    - out_handle -- On success, returns a handle which should be used for subsequent esp_ota_write() and esp_ota_end() calls.

  Returns:

    - ESP_OK: OTA operation commenced successfully.

    - ESP_ERR_INVALID_ARG: partition or out_handle arguments were NULL, or partition doesn't point to an OTA app partition.

    - ESP_ERR_NO_MEM: Cannot allocate memory for OTA operation.

    - ESP_ERR_OTA_PARTITION_CONFLICT: Partition holds the currently running firmware, cannot update in place.

    - ESP_ERR_NOT_FOUND: Partition argument not found in partition table.

    - ESP_ERR_OTA_SELECT_INFO_INVALID: The OTA data partition contains invalid data.

    - ESP_ERR_INVALID_SIZE: Partition doesn't fit in configured flash size.

    - ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash write failed.

    - ESP_ERR_OTA_ROLLBACK_INVALID_STATE: If the running app has not confirmed state. Before performing an update, the application must be valid.

esp_err_t esp_ota_resume(const esp_partition_t *partition, const size_t erase_size, const size_t image_offset, esp_ota_handle_t *out_handle)

  Resume an interrupted OTA update by continuing to write to the specified partition.

  This function is used when an OTA update was previously started and needs to be resumed after an interruption. It continues the OTA process from the specified offset within the partition.

  Unlike esp_ota_begin(), this function does not erase the partition which receives the OTA update, but rather expects that part of the image has already been written correctly, and it resumes writing from the given offset.

  Parameters:

    - partition -- Pointer to info for the partition which is receiving the OTA update. Required.

    - erase_size -- Specifies how much flash memory to erase before resuming OTA, depending on whether a sequential write or a bulk erase is being used.

    - image_offset -- Offset from where to resume the OTA process. Should be set to the number of bytes already written.

    - out_handle -- On success, returns a handle that should be used for subsequent esp_ota_write() and esp_ota_end() calls.

  Returns:

    - ESP_OK: OTA operation resumed successfully.

    - ESP_ERR_INVALID_ARG: partition, out_handle were NULL or image_offset arguments is negative, or partition doesn't point to an OTA app partition.

    - ESP_ERR_NO_MEM: Cannot allocate memory for OTA operation.

    - ESP_ERR_OTA_PARTITION_CONFLICT: Partition holds the currently running firmware, cannot update in place.

    - ESP_ERR_NOT_FOUND: Partition argument not found in partition table.

    - ESP_ERR_OTA_SELECT_INFO_INVALID: The OTA data partition contains invalid data.

    - ESP_ERR_INVALID_SIZE: Partition doesn't fit in configured flash size.

    - ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash write failed.

esp_err_t esp_ota_set_final_partition(esp_ota_handle_t handle, const esp_partition_t *final, bool finalize_with_copy)

  Set the final destination partition for OTA update.

  This function configures the specified final partition as the destination for the OTA update. It also allows setting a flag to indicate if the image should be copied from the staging partition to the final partition after the OTA update completes. Otherwise, copying will need to be handled by custom code using esp_partition_copy().

  Note

  This can be called after esp_ota_begin() and before the OTA update has started (before esp_ota_write()).

  Parameters:

    - handle -- OTA update handle obtained from esp_ota_begin().

    - final -- Pointer to the final destination partition where the new image will be verified and potentially finalized. This partition must not be NULL.

    - finalize_with_copy -- Boolean flag indicating if the downloaded image should be copied from the staging partition to the final partition upon completion. Set to False if you intend to perform the final copy process manually later.

  Returns:

    - ESP_OK: final destination partition set successfully.

    - ESP_ERR_INVALID_STATE: Once the OTA update has started, changing the final destination partition is prohibited.

    - ESP_ERR_INVALID_ARG: Invalid arguments were passed (e.g., final partition is NULL).

    - ESP_ERR_NOT_FOUND: OTA handle not found or final partition verification failed.

esp_err_t esp_ota_write(esp_ota_handle_t handle, const void *data, size_t size)

  Write OTA update data to partition.

  This function can be called multiple times as data is received during the OTA operation. Data is written sequentially to the partition.

  Parameters:

    - handle -- Handle obtained from esp_ota_begin

    - data -- Data buffer to write

    - size -- Size of data buffer in bytes.

  Returns:

    - ESP_OK: Data was written to flash successfully, or size = 0

    - ESP_ERR_INVALID_ARG: handle is invalid.

    - ESP_ERR_OTA_VALIDATE_FAILED: First byte of image contains invalid image magic byte.

    - ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash write failed.

    - ESP_ERR_INVALID_SIZE: if write would go out of bounds of the partition

    - or one of error codes from lower-level flash driver.

esp_err_t esp_ota_write_with_offset(esp_ota_handle_t handle, const void *data, size_t size, uint32_t offset)

  Write OTA update data to partition at an offset.

  This function can write data in non-contiguous manner. If flash encryption is enabled, data should be 16 bytes aligned.

  Note

  While performing OTA, if the packets arrive out of order, esp_ota_write_with_offset() can be used to write data in non-contiguous manner. Use of esp_ota_write_with_offset() in combination with esp_ota_write() is not recommended.

  Parameters:

    - handle -- Handle obtained from esp_ota_begin

    - data -- Data buffer to write

    - size -- Size of data buffer in bytes

    - offset -- Offset in flash partition

  Returns:

    - ESP_OK: Data was written to flash successfully.

    - ESP_ERR_INVALID_ARG: handle is invalid.

    - ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash write failed.

esp_err_t esp_ota_end(esp_ota_handle_t handle)

  Finish OTA update and validate newly written app image.

  If the finalize_with_copy option is set, the staging partition will be copied to the final partition at the end of this function. Otherwise, copying will need to be handled by custom code using esp_partition_copy().

  Note

  After calling esp_ota_end(), the handle is no longer valid and any memory associated with it is freed (regardless of result).

  Note

  If either the final or staging partitions were for the bootloader, then at the end of this function, the bootloader is reset to its default offset: esp_image_bootloader_offset_set(ESP_PRIMARY_BOOTLOADER_OFFSET)

  Parameters:

    handle -- Handle obtained from esp_ota_begin().

  Returns:

    - ESP_OK: Newly written OTA app image is valid.

    - ESP_ERR_NOT_FOUND: OTA handle was not found.

    - ESP_ERR_INVALID_ARG: Handle was never written to.

    - ESP_ERR_OTA_VALIDATE_FAILED: OTA image is invalid (either not a valid app image, or - if secure boot is enabled - signature failed to verify.)

    - ESP_ERR_INVALID_STATE: If flash encryption is enabled, this result indicates an internal error writing the final encrypted bytes to flash.

esp_err_t esp_ota_abort(esp_ota_handle_t handle)

  Abort OTA update, free the handle and memory associated with it.

  Parameters:

    handle -- obtained from esp_ota_begin().

  Returns:

    - ESP_OK: Handle and its associated memory is freed successfully.

    - ESP_ERR_NOT_FOUND: OTA handle was not found.

esp_err_t esp_ota_set_boot_partition(const esp_partition_t *partition)

  Configure OTA data for a new boot partition.

  Note

  If this function returns ESP_OK, calling esp_restart() will boot the newly configured app partition.

  Parameters:

    partition -- Pointer to info for partition containing app image to boot.

  Returns:

    - ESP_OK: OTA data updated, next reboot will use specified partition.

    - ESP_ERR_INVALID_ARG: partition argument was NULL or didn't point to a valid OTA partition of type "app".

    - ESP_ERR_OTA_VALIDATE_FAILED: Partition contained invalid app image. Also returned if secure boot is enabled and signature validation failed.

    - ESP_ERR_NOT_FOUND: OTA data partition not found.

    - ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash erase or write failed.

const esp_partition_t *esp_ota_get_boot_partition(void)

  Get partition info of currently configured boot app.

  If esp_ota_set_boot_partition() has been called, the partition which was set by that function will be returned.

  If esp_ota_set_boot_partition() has not been called, the result is usually the same as esp_ota_get_running_partition(). The two results are not equal if the configured boot partition does not contain a valid app (meaning that the running partition will be an app that the bootloader chose via fallback).

  If the OTA data partition is not present or not valid then the result is the first app partition found in the partition table. In priority order, this means: the factory app, the first OTA app slot, or the test app partition.

  Note that there is no guarantee the returned partition is a valid app. Use esp_image_verify(ESP_IMAGE_VERIFY, ...) to verify if the returned partition contains a bootable image.

  Returns:

    Pointer to info for partition structure, or NULL if partition table is invalid or a flash read operation failed. Any returned pointer is valid for the lifetime of the application.

const esp_partition_t *esp_ota_get_running_partition(void)

  Get partition info of currently running app.

  This function is different to esp_ota_get_boot_partition() in that it ignores any change of selected boot partition caused by esp_ota_set_boot_partition(). Only the app whose code is currently running will have its partition information returned.

  The partition returned by this function may also differ from esp_ota_get_boot_partition() if the configured boot partition is somehow invalid, and the bootloader fell back to a different app partition at boot.

  Returns:

    Pointer to info for partition structure, or NULL if no partition is found or flash read operation failed. Returned pointer is valid for the lifetime of the application.

const esp_partition_t *esp_ota_get_next_update_partition(const esp_partition_t *start_from)

  Return the next OTA app partition which should be written with a new firmware.

  Call this function to find an OTA app partition which can be passed to esp_ota_begin().

  Finds next partition round-robin, starting from the current running partition.

  Parameters:

    start_from -- If set, treat this partition info as describing the current running partition. Can be NULL, in which case esp_ota_get_running_partition() is used to find the currently running partition. The result of this function is never the same as this argument.

  Returns:

    Pointer to info for partition which should be updated next. NULL result indicates invalid OTA data partition, or that no eligible OTA app slot partition was found.

esp_err_t esp_ota_get_partition_description(const esp_partition_t *partition, esp_app_desc_t *app_desc)

  Returns esp_app_desc structure for app partition. This structure includes app version.

  Returns a description for the requested app partition.

  Parameters:

    - partition -- [in] Pointer to app partition. (only app partition)

    - app_desc -- [out] Structure of info about app.

  Returns:

    - ESP_OK Successful.

    - ESP_ERR_NOT_FOUND app_desc structure is not found. Magic word is incorrect.

    - ESP_ERR_NOT_SUPPORTED Partition is not application.

    - ESP_ERR_INVALID_ARG Arguments is NULL or if partition's offset exceeds partition size.

    - ESP_ERR_INVALID_SIZE Read would go out of bounds of the partition.

    - or one of error codes from lower-level flash driver.

esp_err_t esp_ota_get_bootloader_description(const esp_partition_t *bootloader_partition, esp_bootloader_desc_t *desc)

  Returns the description structure of the bootloader.

  Parameters:

    - bootloader_partition -- [in] Pointer to bootloader partition. If NULL, then the PRIMARY bootloader is used (the default location). offset = CONFIG_BOOTLOADER_OFFSET_IN_FLASH, size = CONFIG_PARTITION_TABLE_OFFSET - CONFIG_BOOTLOADER_OFFSET_IN_FLASH,

    - desc -- [out] Structure of info about bootloader.

  Returns:

    - ESP_OK Successful.

    - ESP_ERR_NOT_FOUND Description structure is not found in the bootloader image. Magic byte is incorrect.

    - ESP_ERR_INVALID_ARG Arguments is NULL.

    - ESP_ERR_INVALID_SIZE Read would go out of bounds of the partition.

    - or one of error codes from lower-level flash driver.

esp_err_t esp_ota_invalidate_inactive_ota_data_slot(void)

  Invalidate the OTA data slot associated with the last boot application partition.

  This function erases the OTA data slot corresponding to the last boot application partition, making the partition invalid for booting in future. The application partition itself is not erased, preserving its contents.

  Returns:

    - ESP_OK: Successfully invalidated the OTA data slot.

    - ESP_FAIL: Failed to invalidate the OTA data slot (e.g., invalid parameters, no OTA data partition, or other errors).

    - Other error codes from `esp_partition_erase_range`.

uint8_t esp_ota_get_app_partition_count(void)

  Returns number of ota partitions provided in partition table.

  Returns:

    - Number of OTA partitions

esp_err_t esp_ota_mark_app_valid_cancel_rollback(void)

  This function is called to indicate that the running app is working well.

  Returns:

    - ESP_OK: if successful.

esp_err_t esp_ota_mark_app_invalid_rollback(void)

  This function is called to roll back to the previously workable app without reboot.

  Checks applications on a flash drive that can be booted in case of rollback. If the flash does not have at least one app (except the running app) then rollback is not possible.

  Returns:

    - ESP_OK: if successful.

    - ESP_FAIL: if not successful.

    - ESP_ERR_OTA_ROLLBACK_FAILED: The rollback is not possible because the available OTA partitions on the flash do not contain a valid application.

esp_err_t esp_ota_mark_app_invalid_rollback_and_reboot(void)

  This function is called to roll back to the previously workable app with reboot.

  Equivalent to calling esp_ota_mark_app_invalid_rollback(), and, if successful, followed by esp_restart().

  Returns:

    - ESP_FAIL: if not successful.

    - ESP_ERR_OTA_ROLLBACK_FAILED: The rollback is not possible due to flash does not have any apps.

const esp_partition_t *esp_ota_get_last_invalid_partition(void)

  Returns last partition with invalid state (ESP_OTA_IMG_INVALID or ESP_OTA_IMG_ABORTED).

  Returns:

    partition.

esp_err_t esp_ota_get_state_partition(const esp_partition_t *partition, esp_ota_img_states_t *ota_state)

  Returns state for given partition.

  Parameters:

    - partition -- [in] Pointer to partition.

    - ota_state -- [out] state of partition (if this partition has a record in otadata).

  Returns:

    - ESP_OK: Successful.

    - ESP_ERR_INVALID_ARG: partition or ota_state arguments were NULL.

    - ESP_ERR_NOT_SUPPORTED: partition is not ota.

    - ESP_ERR_NOT_FOUND: Partition table does not have otadata or state was not found for given partition.

esp_err_t esp_ota_erase_last_boot_app_partition(void)

  Erase previous boot app partition and corresponding otadata select for this partition.

  When current app is marked to as valid then you can erase previous app partition.

  Returns:

    - ESP_OK: Successful, otherwise ESP_ERR.

bool esp_ota_check_rollback_is_possible(void)

  Checks applications on the slots which can be booted in case of rollback.

  These applications should be valid (marked in otadata as not UNDEFINED, INVALID or ABORTED and crc is good) and be able booted, and secure_version of app >= secure_version of efuse (if anti-rollback is enabled).

  Returns:

    - True: Returns true if the slots have at least one app (except the running app).

    - False: The rollback is not possible.

esp_err_t esp_ota_revoke_secure_boot_public_key(esp_ota_secure_boot_public_key_index_t index)

  Revokes the signature digest denoted by the given index. This should be called in the application only after the rollback logic otherwise the device may end up in unrecoverable state.

  Relevant for Secure boot v2 on ESP32-S2, ESP32-S3, ESP32-C3, ESP32-C6, ESP32-H2 where up to 3 key digests can be stored (Key #N-1, Key #N, Key #N+1). When a key used to sign an app is invalidated, an OTA update is to be sent with an app signed with at least one of the other two keys which has not been revoked already. After successfully booting the OTA app should call this function to revoke Key #N-1.

  Parameters:

    index -- - The index of the signature block to be revoked

  Returns:

    - ESP_OK: If revocation is successful.

    - ESP_ERR_INVALID_ARG: If the index of the public key to be revoked is incorrect.

    - ESP_FAIL: If secure boot v2 has not been enabled.

### Macros

OTA_SIZE_UNKNOWN

  Used for esp_ota_begin() if new image size is unknown

OTA_WITH_SEQUENTIAL_WRITES

  Used for esp_ota_begin() if new image size is unknown and erase can be done in incremental manner (assuming write operation is in continuous sequence)

ESP_ERR_OTA_BASE

  Base error code for ota_ops api

ESP_ERR_OTA_PARTITION_CONFLICT

  Error if request was to write or erase the current running partition

ESP_ERR_OTA_SELECT_INFO_INVALID

  Error if OTA data partition contains invalid content

ESP_ERR_OTA_VALIDATE_FAILED

  Error if OTA app image is invalid

ESP_ERR_OTA_SMALL_SEC_VER

  Error if the firmware has a secure version less than the running firmware.

ESP_ERR_OTA_ROLLBACK_FAILED

  Error if flash does not have valid firmware in passive partition and hence rollback is not possible

ESP_ERR_OTA_ROLLBACK_INVALID_STATE

  Error if current active firmware is still marked in pending validation state (ESP_OTA_IMG_PENDING_VERIFY), essentially first boot of firmware image post upgrade and hence firmware upgrade is not possible

### Type Definitions

typedef uint32_t esp_ota_handle_t

  Opaque handle for an application OTA update.

  esp_ota_begin() returns a handle which is then used for subsequent calls to esp_ota_write() and esp_ota_end().

### Enumerations

enum esp_ota_secure_boot_public_key_index_t

  Secure Boot V2 public key indexes.

  Values:

  enumerator SECURE_BOOT_PUBLIC_KEY_INDEX_0

    Points to the 0th index of the Secure Boot v2 public key

  enumerator SECURE_BOOT_PUBLIC_KEY_INDEX_1

    Points to the 1st index of the Secure Boot v2 public key

  enumerator SECURE_BOOT_PUBLIC_KEY_INDEX_2

    Points to the 2nd index of the Secure Boot v2 public key

## Debugging OTA Failure

How to Debug When OTA Fails (click to enlarge)

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