Miscellaneous System APIs

Software Reset

To perform software reset of the chip, the esp_restart() function is provided. When the function is called, execution of the program stops, both CPUs are reset, and the application is loaded by the bootloader and starts execution again.

Additionally, the esp_register_shutdown_handler() function can register a routine that will be automatically called before a restart (that is triggered by esp_restart()) occurs. This is similar to the functionality of atexit POSIX function.

Reset Reason

ESP-IDF applications can be started or restarted due to a variety of reasons. To get the last reset reason, call esp_reset_reason() function. See description of esp_reset_reason_t for the list of possible reset reasons.

Heap Memory

Two heap-memory-related functions are provided:

esp_get_free_heap_size() returns the current size of free heap memory.
esp_get_minimum_free_heap_size() returns the minimum size of free heap memory that has ever been available (i.e., the smallest size of free heap memory in the applications lifetime).

Note that ESP-IDF supports multiple heaps with different capabilities. The functions mentioned in this section return the size of heap memory that can be allocated using the malloc family of functions. For further information about heap memory, see Heap Memory Allocation.

MAC Address

These APIs allow querying and customizing MAC addresses for different supported network interfaces (e.g., Wi-Fi, Bluetooth, Ethernet).

To fetch the MAC address for a specific network interface (e.g., Wi-Fi, Bluetooth, Ethernet), call the function esp_read_mac().

In ESP-IDF, the MAC addresses for the various network interfaces are calculated from a single base MAC address. By default, the Espressif base MAC address is used. This base MAC address is pre-programmed into the ESP32 eFuse in the factory during production.

Interface	MAC Address (4 universally administered, default)	MAC Address (2 universally administered)
Wi-Fi Station	base_mac	base_mac
Wi-Fi SoftAP	base_mac, +1 to the last octet	Local MAC (derived from Wi-Fi Station MAC)
Bluetooth	base_mac, +2 to the last octet	base_mac, +1 to the last octet
Ethernet	base_mac, +3 to the last octet	Local MAC (derived from Bluetooth MAC)

Note

The configuration configures the number of universally administered MAC addresses that are provided by Espressif.

Custom Base MAC

The default base MAC is pre-programmed by Espressif in eFuse BLK0. To set a custom base MAC instead, call the function esp_base_mac_addr_set() before initializing any network interfaces or calling the esp_read_mac() function. The custom MAC address can be stored in any supported storage device (e.g., flash, NVS).

The custom base MAC addresses should be allocated such that derived MAC addresses will not overlap. Based on the table above, users can configure the option CONFIG_ESP32_UNIVERSAL_MAC_ADDRESSES to set the number of valid universal MAC addresses that can be derived from the custom base MAC.

Note

It is also possible to call the function esp_netif_set_mac() to set the specific MAC used by a network interface after network initialization. But it is recommended to use the base MAC approach documented here to avoid the possibility of the original MAC address briefly appearing on the network before being changed.

Custom MAC Address in eFuse

When reading custom MAC addresses from eFuse, ESP-IDF provides a helper function esp_efuse_mac_get_custom(). This loads the MAC address from eFuse BLK3. This function assumes that the custom base MAC address is stored in the following format:

Field	# of bits	Range of bits	Notes
Version	8	191:184	0: invalid, others — valid
Reserved	128	183:56
MAC address	48	55:8
MAC address CRC	8	7:0	CRC-8-CCITT, polynomial 0x07

Note

If the 3/4 coding scheme is enabled, all eFuse fields in this block must be burnt at the same time.

Once MAC address has been obtained using esp_efuse_mac_get_custom(), call esp_base_mac_addr_set() to set this MAC address as base MAC address.

Local vs Universal MAC Addresses

ESP32 comes pre-programmed with enough valid Espressif universally administered MAC addresses for all internal interfaces. The table above shows how to calculate and derive the MAC address for a specific interface according to the base MAC address.

When using a custom MAC address scheme, it is possible that not all interfaces can be assigned with a universally administered MAC address. In these cases, a locally administered MAC address is assigned. Note that these addresses are intended for use on a single local network only.

See this article for the definition of locally and universally administered MAC addresses.

Function esp_derive_local_mac() is called internally to derive a local MAC address from a universal MAC address. The process is as follows:

The U/L bit (bit value 0x2) is set in the first octet of the universal MAC address, creating a local MAC address.
If this bit is already set in the supplied universal MAC address (i.e., the supplied “universal” MAC address was in fact already a local MAC address), then the first octet of the local MAC address is XORed with 0x4.

Chip Version

esp_chip_info() function fills esp_chip_info_t structure with information about the chip. This includes the chip revision, number of CPU cores, and a bit mask of features enabled in the chip.

SDK Version

esp_get_idf_version() returns a string describing the ESP-IDF version which is used to compile the application. This is the same value as the one available through IDF_VER variable of the build system. The version string generally has the format of git describe output.

To get the version at build time, additional version macros are provided. They can be used to enable or disable parts of the program depending on the ESP-IDF version.

ESP_IDF_VERSION_MAJOR, ESP_IDF_VERSION_MINOR, ESP_IDF_VERSION_PATCH are defined to integers representing major, minor, and patch version.

ESP_IDF_VERSION_VAL and ESP_IDF_VERSION can be used when implementing version checks:

#include "esp_idf_version.h"

#if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(4, 0, 0)
    // enable functionality present in ESP-IDF v4.0
#endif

App Version

The application version is stored in esp_app_desc_t structure. It is located in DROM sector and has a fixed offset from the beginning of the binary file. The structure is located after esp_image_header_t and esp_image_segment_header_t structures. The type of the field version is string and it has a maximum length of 32 chars.

To set the version in your project manually, you need to set the PROJECT_VER variable in the CMakeLists.txt of your project. In application CMakeLists.txt, put set(PROJECT_VER "0.1.0.1") before including project.cmake.

If the CONFIG_APP_PROJECT_VER_FROM_CONFIG option is set, the value of CONFIG_APP_PROJECT_VER will be used. Otherwise, if the PROJECT_VER variable is not set in the project, it will be retrieved either from the $(PROJECT_PATH)/version.txt file (if present) or using git command git describe. If neither is available, PROJECT_VER will be set to “1”. Application can make use of this by calling esp_ota_get_app_description() or esp_ota_get_partition_description() functions.

API Reference

Header File

components/esp_system/include/esp_system.h

Functions

esp_err_t esp_register_shutdown_handler(shutdown_handler_t handle)

Register shutdown handler.

This function allows you to register a handler that gets invoked before the application is restarted using esp_restart function.

Parameters

handle – function to execute on restart

Returns

ESP_OK on success
ESP_ERR_INVALID_STATE if the handler has already been registered
ESP_ERR_NO_MEM if no more shutdown handler slots are available

esp_err_t esp_unregister_shutdown_handler(shutdown_handler_t handle)

Unregister shutdown handler.

This function allows you to unregister a handler which was previously registered using esp_register_shutdown_handler function.

ESP_OK on success
ESP_ERR_INVALID_STATE if the given handler hasn’t been registered before

void esp_restart(void)

Restart PRO and APP CPUs.

This function can be called both from PRO and APP CPUs. After successful restart, CPU reset reason will be SW_CPU_RESET. Peripherals (except for Wi-Fi, BT, UART0, SPI1, and legacy timers) are not reset. This function does not return.

esp_reset_reason_t esp_reset_reason(void)

Get reason of last reset.

Returns: See description of esp_reset_reason_t for explanation of each value.

uint32_t esp_get_free_heap_size(void)

Get the size of available heap.

Note

Note that the returned value may be larger than the maximum contiguous block which can be allocated.

Returns: Available heap size, in bytes.

uint32_t esp_get_free_internal_heap_size(void)

Get the size of available internal heap.

Note

Note that the returned value may be larger than the maximum contiguous block which can be allocated.

Returns: Available internal heap size, in bytes.

uint32_t esp_get_minimum_free_heap_size(void)

Get the minimum heap that has ever been available.

Returns: Minimum free heap ever available

void esp_system_abort(const char *details)

Trigger a software abort.

Parameters: details – Details that will be displayed during panic handling.

Type Definitions

typedef void (*shutdown_handler_t)(void): Shutdown handler type

Enumerations

enum esp_reset_reason_t

Reset reasons.

Values:

enumerator ESP_RST_UNKNOWN: Reset reason can not be determined.

enumerator ESP_RST_POWERON: Reset due to power-on event.

enumerator ESP_RST_EXT: Reset by external pin (not applicable for ESP32)

enumerator ESP_RST_SW: Software reset via esp_restart.

enumerator ESP_RST_PANIC: Software reset due to exception/panic.

enumerator ESP_RST_INT_WDT: Reset (software or hardware) due to interrupt watchdog.

enumerator ESP_RST_TASK_WDT: Reset due to task watchdog.

enumerator ESP_RST_WDT: Reset due to other watchdogs.

enumerator ESP_RST_DEEPSLEEP: Reset after exiting deep sleep mode.

enumerator ESP_RST_BROWNOUT: Brownout reset (software or hardware)

enumerator ESP_RST_SDIO: Reset over SDIO.

Header File

components/esp_common/include/esp_idf_version.h

Functions

const char *esp_get_idf_version(void)

Return full IDF version string, same as ‘git describe’ output.

Note

If you are printing the ESP-IDF version in a log file or other information, this function provides more information than using the numerical version macros. For example, numerical version macros don’t differentiate between development, pre-release and release versions, but the output of this function does.

Returns: constant string from IDF_VER

Macros

ESP_IDF_VERSION_MAJOR: Major version number (X.x.x)

ESP_IDF_VERSION_MINOR: Minor version number (x.X.x)

ESP_IDF_VERSION_PATCH: Patch version number (x.x.X)

ESP_IDF_VERSION_VAL(major, minor, patch)

Macro to convert IDF version number into an integer

To be used in comparisons, such as ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(4, 0, 0)

ESP_IDF_VERSION

Current IDF version, as an integer

To be used in comparisons, such as ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(4, 0, 0)

Header File

components/esp_hw_support/include/esp_mac.h

Functions

esp_err_t esp_base_mac_addr_set(const uint8_t *mac)

Set base MAC address with the MAC address which is stored in BLK3 of EFUSE or external storage e.g. flash and EEPROM.

Base MAC address is used to generate the MAC addresses used by network interfaces.

If using a custom base MAC address, call this API before initializing any network interfaces. Refer to the ESP-IDF Programming Guide for details about how the Base MAC is used.

Note

Base MAC must be a unicast MAC (least significant bit of first byte must be zero).

Note

If not using a valid OUI, set the “locally administered” bit (bit value 0x02 in the first byte) to avoid collisions.

Parameters: mac – base MAC address, length: 6 bytes/8 bytes. length: 6 bytes for MAC-48 8 bytes for EUI-64(used for IEEE 802.15.4)
Returns: ESP_OK on success ESP_ERR_INVALID_ARG If mac is NULL or is not a unicast MAC

esp_err_t esp_base_mac_addr_get(uint8_t *mac)

Return base MAC address which is set using esp_base_mac_addr_set.

Note

If no custom Base MAC has been set, this returns the pre-programmed Espressif base MAC address.

Parameters: mac – base MAC address, length: 6 bytes/8 bytes. length: 6 bytes for MAC-48 8 bytes for EUI-64(used for IEEE 802.15.4)
Returns: ESP_OK on success ESP_ERR_INVALID_ARG mac is NULL ESP_ERR_INVALID_MAC base MAC address has not been set

esp_err_t esp_efuse_mac_get_custom(uint8_t *mac)

Return base MAC address which was previously written to BLK3 of EFUSE.

Base MAC address is used to generate the MAC addresses used by the networking interfaces. This API returns the custom base MAC address which was previously written to EFUSE BLK3 in a specified format.

Writing this EFUSE allows setting of a different (non-Espressif) base MAC address. It is also possible to store a custom base MAC address elsewhere, see esp_base_mac_addr_set() for details.

Note

This function is currently only supported on ESP32.

Parameters: mac – base MAC address, length: 6 bytes/8 bytes. length: 6 bytes for MAC-48 8 bytes for EUI-64(used for IEEE 802.15.4)
Returns: ESP_OK on success ESP_ERR_INVALID_ARG mac is NULL ESP_ERR_INVALID_MAC CUSTOM_MAC address has not been set, all zeros (for esp32-xx) ESP_ERR_INVALID_VERSION An invalid MAC version field was read from BLK3 of EFUSE (for esp32) ESP_ERR_INVALID_CRC An invalid MAC CRC was read from BLK3 of EFUSE (for esp32)

esp_err_t esp_efuse_mac_get_default(uint8_t *mac)

Return base MAC address which is factory-programmed by Espressif in EFUSE.

Parameters: mac – base MAC address, length: 6 bytes/8 bytes. length: 6 bytes for MAC-48 8 bytes for EUI-64(used for IEEE 802.15.4)
Returns: ESP_OK on success ESP_ERR_INVALID_ARG mac is NULL

esp_err_t esp_read_mac(uint8_t *mac, esp_mac_type_t type)

Read base MAC address and set MAC address of the interface.

This function first get base MAC address using esp_base_mac_addr_get(). Then calculates the MAC address of the specific interface requested, refer to ESP-IDF Programming Guide for the algorithm.

Parameters

mac – base MAC address, length: 6 bytes/8 bytes. length: 6 bytes for MAC-48 8 bytes for EUI-64(used for IEEE 802.15.4)
type – Type of MAC address to return

Returns

ESP_OK on success

esp_err_t esp_derive_local_mac(uint8_t *local_mac, const uint8_t *universal_mac)

Derive local MAC address from universal MAC address.

This function copies a universal MAC address and then sets the “locally

administered” bit (bit 0x2) in the first octet, creating a locally administered MAC address.

If the universal MAC address argument is already a locally administered MAC address, then the first octet is XORed with 0x4 in order to create a different locally administered MAC address.

Parameters

local_mac – base MAC address, length: 6 bytes/8 bytes. length: 6 bytes for MAC-48 8 bytes for EUI-64(used for IEEE 802.15.4)
universal_mac – Source universal MAC address, length: 6 bytes.

Returns

ESP_OK on success

Macros

MAC2STR(a)

MACSTR

Enumerations

enum esp_mac_type_t

Values:

enumerator ESP_MAC_WIFI_STA

enumerator ESP_MAC_WIFI_SOFTAP

enumerator ESP_MAC_BT

enumerator ESP_MAC_ETH

enumerator ESP_MAC_IEEE802154

Header File

components/esp_hw_support/include/esp_chip_info.h

Functions

void esp_chip_info(esp_chip_info_t *out_info)

Fill an esp_chip_info_t structure with information about the chip.

Parameters: out_info – [out] structure to be filled

Structures

struct esp_chip_info_t

The structure represents information about the chip.

Public Members

esp_chip_model_t model: chip model, one of esp_chip_model_t

uint32_t features: bit mask of CHIP_FEATURE_x feature flags

uint16_t revision: chip revision number (in format MXX; where M - wafer major version, XX - wafer minor version)

uint8_t cores: number of CPU cores

Macros

CHIP_FEATURE_EMB_FLASH: Chip has embedded flash memory.

CHIP_FEATURE_WIFI_BGN: Chip has 2.4GHz WiFi.

CHIP_FEATURE_BLE: Chip has Bluetooth LE.

CHIP_FEATURE_BT: Chip has Bluetooth Classic.

CHIP_FEATURE_IEEE802154: Chip has IEEE 802.15.4.

CHIP_FEATURE_EMB_PSRAM: Chip has embedded psram.

Enumerations

enum esp_chip_model_t

Chip models.

Values:

enumerator CHIP_ESP32: ESP32.

enumerator CHIP_ESP32S2: ESP32-S2.

enumerator CHIP_ESP32S3: ESP32-S3.

enumerator CHIP_ESP32C3: ESP32-C3.

enumerator CHIP_ESP32H2: ESP32-H2.

enumerator CHIP_ESP32C2: ESP32-C2.

Header File

components/esp_hw_support/include/esp_cpu.h

Functions

void esp_cpu_stall(int core_id)

Stall a CPU core.

Parameters: core_id – The core’s ID

void esp_cpu_unstall(int core_id)

Resume a previously stalled CPU core.

Parameters: core_id – The core’s ID

void esp_cpu_reset(int core_id)

Reset a CPU core.

Parameters: core_id – The core’s ID

void esp_cpu_wait_for_intr(void)

Wait for Interrupt.

This function causes the current CPU core to execute its Wait For Interrupt (WFI or equivalent) instruction. After executing this function, the CPU core will stop execution until an interrupt occurs.

int esp_cpu_get_core_id(void)

Get the current core’s ID.

This function will return the ID of the current CPU (i.e., the CPU that calls this function).

Returns: The current core’s ID [0..SOC_CPU_CORES_NUM - 1]

void *esp_cpu_get_sp(void)

Read the current stack pointer address.

Returns: Stack pointer address

esp_cpu_cycle_count_t esp_cpu_get_cycle_count(void)

Get the current CPU core’s cycle count.

Each CPU core maintains an internal counter (i.e., cycle count) that increments every CPU clock cycle.

Returns: Current CPU’s cycle count, 0 if not supported.

void esp_cpu_set_cycle_count(esp_cpu_cycle_count_t cycle_count)

Set the current CPU core’s cycle count.

Set the given value into the internal counter that increments every CPU clock cycle.

Parameters: cycle_count – CPU cycle count

void *esp_cpu_pc_to_addr(uint32_t pc)

Convert a program counter (PC) value to address.

If the architecture does not store the true virtual address in the CPU’s PC or return addresses, this function will convert the PC value to a virtual address. Otherwise, the PC is just returned

Parameters: pc – PC value
Returns: Virtual address

void esp_cpu_intr_get_desc(int core_id, int intr_num, esp_cpu_intr_desc_t *intr_desc_ret)

Get a CPU interrupt’s descriptor.

Each CPU interrupt has a descriptor describing the interrupt’s capabilities and restrictions. This function gets the descriptor of a particular interrupt on a particular CPU.

Parameters

core_id – [in] The core’s ID
intr_num – [in] Interrupt number
intr_desc_ret – [out] The interrupt’s descriptor

void esp_cpu_intr_set_ivt_addr(const void *ivt_addr)

Set the base address of the current CPU’s Interrupt Vector Table (IVT)

Parameters: ivt_addr – Interrupt Vector Table’s base address

bool esp_cpu_intr_has_handler(int intr_num)

Check if a particular interrupt already has a handler function.

Check if a particular interrupt on the current CPU already has a handler function assigned.

Note

This function simply checks if the IVT of the current CPU already has a handler assigned.

Parameters: intr_num – Interrupt number (from 0 to 31)
Returns: True if the interrupt has a handler function, false otherwise.

void esp_cpu_intr_set_handler(int intr_num, esp_cpu_intr_handler_t handler, void *handler_arg)

Set the handler function of a particular interrupt.

Assign a handler function (i.e., ISR) to a particular interrupt on the current CPU.

Note

This function simply sets the handler function (in the IVT) and does not actually enable the interrupt.

Parameters

intr_num – Interrupt number (from 0 to 31)
handler – Handler function
handler_arg – Argument passed to the handler function

void *esp_cpu_intr_get_handler_arg(int intr_num)

Get a handler function’s argument of.

Get the argument of a previously assigned handler function on the current CPU.

Parameters: intr_num – Interrupt number (from 0 to 31)
Returns: The the argument passed to the handler function

void esp_cpu_intr_enable(uint32_t intr_mask)

Enable particular interrupts on the current CPU.

Parameters: intr_mask – Bit mask of the interrupts to enable

void esp_cpu_intr_disable(uint32_t intr_mask)

Disable particular interrupts on the current CPU.

Parameters: intr_mask – Bit mask of the interrupts to disable

uint32_t esp_cpu_intr_get_enabled_mask(void)

Get the enabled interrupts on the current CPU.

Returns: Bit mask of the enabled interrupts

void esp_cpu_intr_edge_ack(int intr_num)

Acknowledge an edge interrupt.

Parameters: intr_num – Interrupt number (from 0 to 31)

void esp_cpu_configure_region_protection(void): Configure the CPU to disable access to invalid memory regions.

esp_err_t esp_cpu_set_breakpoint(int bp_num, const void *bp_addr)

Set and enable a hardware breakpoint on the current CPU.

Note

This function is meant to be called by the panic handler to set a breakpoint for an attached debugger during a panic.

Note

Overwrites previously set breakpoint with same breakpoint number.

Parameters

bp_num – Hardware breakpoint number [0..SOC_CPU_BREAKPOINTS_NUM - 1]
bp_addr – Address to set a breakpoint on

Returns

ESP_OK if breakpoint is set. Failure otherwise

esp_err_t esp_cpu_clear_breakpoint(int bp_num)

Clear a hardware breakpoint on the current CPU.

Note

Clears a breakpoint regardless of whether it was previously set

Parameters: bp_num – Hardware breakpoint number [0..SOC_CPU_BREAKPOINTS_NUM - 1]
Returns: ESP_OK if breakpoint is cleared. Failure otherwise

esp_err_t esp_cpu_set_watchpoint(int wp_num, const void *wp_addr, size_t size, esp_cpu_watchpoint_trigger_t trigger)

Set and enable a hardware watchpoint on the current CPU.

Set and enable a hardware watchpoint on the current CPU, specifying the memory range and trigger operation. Watchpoints will break/panic the CPU when the CPU accesses (according to the trigger type) on a certain memory range.

Note

Overwrites previously set watchpoint with same watchpoint number.

Parameters

wp_num – Hardware watchpoint number [0..SOC_CPU_WATCHPOINTS_NUM - 1]
wp_addr – Watchpoint’s base address
size – Size of the region to watch. Must be one of 2^n, with n in [0..6].
trigger – Trigger type

Returns

ESP_ERR_INVALID_ARG on invalid arg, ESP_OK otherwise

esp_err_t esp_cpu_clear_watchpoint(int wp_num)

Clear a hardware watchpoint on the current CPU.

Note

Clears a watchpoint regardless of whether it was previously set

Parameters: wp_num – Hardware watchpoint number [0..SOC_CPU_WATCHPOINTS_NUM - 1]
Returns: ESP_OK if watchpoint was cleared. Failure otherwise.

bool esp_cpu_dbgr_is_attached(void)

Check if the current CPU has a debugger attached.

Returns: True if debugger is attached, false otherwise

void esp_cpu_dbgr_break(void): Trigger a call to the current CPU’s attached debugger.

intptr_t esp_cpu_get_call_addr(intptr_t return_address)

Given the return address, calculate the address of the preceding call instruction This is typically used to answer the question “where was the function called from?”.

Parameters: return_address – The value of the return address register. Typically set to the value of __builtin_return_address(0).
Returns: Address of the call instruction preceding the return address.

bool esp_cpu_compare_and_set(volatile uint32_t *addr, uint32_t compare_value, uint32_t new_value)

Atomic compare-and-set operation.

Parameters

addr – Address of atomic variable
compare_value – Value to compare the atomic variable to
new_value – New value to set the atomic variable to

Returns

Whether the atomic variable was set or not

Structures

struct esp_cpu_intr_desc_t

CPU interrupt descriptor.

Each particular CPU interrupt has an associated descriptor describing that particular interrupt’s characteristics. Call esp_cpu_intr_get_desc() to get the descriptors of a particular interrupt.

Public Members

int priority: Priority of the interrupt if it has a fixed priority, (-1) if the priority is configurable.

esp_cpu_intr_type_t type: Whether the interrupt is an edge or level type interrupt, ESP_CPU_INTR_TYPE_NA if the type is configurable.

uint32_t flags: Flags indicating extra details.

Macros

ESP_CPU_INTR_DESC_FLAG_SPECIAL

Interrupt descriptor flags of esp_cpu_intr_desc_t.

The interrupt is a special interrupt (e.g., a CPU timer interrupt)

ESP_CPU_INTR_DESC_FLAG_RESVD: The interrupt is reserved for internal use

Type Definitions

typedef uint32_t esp_cpu_cycle_count_t

CPU cycle count type.

This data type represents the CPU’s clock cycle count

typedef void (*esp_cpu_intr_handler_t)(void *arg): CPU interrupt handler type.

Enumerations

enum esp_cpu_intr_type_t

CPU interrupt type.

Values:

enumerator ESP_CPU_INTR_TYPE_LEVEL

enumerator ESP_CPU_INTR_TYPE_EDGE

enumerator ESP_CPU_INTR_TYPE_NA

enum esp_cpu_watchpoint_trigger_t

CPU watchpoint trigger type.

Values:

enumerator ESP_CPU_WATCHPOINT_LOAD

enumerator ESP_CPU_WATCHPOINT_STORE

enumerator ESP_CPU_WATCHPOINT_ACCESS

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