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Miscellaneous System APIs

{IDF_TARGET_BASE_MAC_BLOCK: default="BLK1", esp32="BLK0"}

Software reset

To perform software reset of the chip, :cppesp_restart function is provided. When the function is called, execution of the program will stop, both CPUs will be reset, application will be loaded by the bootloader and started again.

Additionally, :cppesp_register_shutdown_handler function is provided to register a routine which needs to be called prior to restart (when done by :cppesp_restart). This is similar to the functionality of atexit POSIX function.

Reset reason

ESP-IDF application can be started or restarted due to a variety of reasons. To get the last reset reason, call :cppesp_reset_reason function. See description of :cppesp_reset_reason_t for the list of possible reset reasons.

Heap memory

Two heap memory related functions are provided:

  • :cppesp_get_free_heap_size returns the current size of free heap memory
  • :cppesp_get_minimum_free_heap_size returns the minimum size of free heap memory that was available during program execution.

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

MAC Address

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

SOC_BT_SUPPORTED

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

not SOC_BT_SUPPORTED

To fetch MAC address for a specific interface (e.g. Wi-Fi Station, Wi-Fi SoftAP), call the function :cppesp_read_mac function.

In ESP-IDF these addresses are calculated from a single Base MAC address. By default, the Espressif base MAC address is used. This MAC is pre-programmed into {IDF_TARGET_NAME} eFuse from the factory.

not esp32s2

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 <local-mac-addresses> 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 <local-mac-addresses> (derived from Bluetooth MAC)

Note

The default configuration <CONFIG_{IDF_TARGET_CFG_PREFIX}_UNIVERSAL_MAC_ADDRESSES> is 4 universally administered MAC addresses, and this is recommended when using Espressif-provided MAC addresses.

esp32s2

Interface MAC address (2 universally administered, default) MAC address (1 universally administered)
Wi-Fi Station base_mac base_mac
Wi-Fi SoftAP base_mac, +1 to the last octet Local MAC <local-mac-addresses> (derived from Wi-Fi Station MAC)
Ethernet (see note) Local MAC <local-mac-addresses> (derived from Wi-Fi SoftAP MAC Local MAC <local-mac-addresses> (derived from base_mac with +1 to last octet. Not recommended.)

Note

The default configuration <CONFIG_{IDF_TARGET_CFG_PREFIX}_UNIVERSAL_MAC_ADDRESSES> is 2 universally administered MAC addresses, and this is recommended when using Espressif-provided MAC addresses.

not SOC_EMAC_SUPPORTED

Note

{IDF_TARGET_NAME} has no integrated Ethernet MAC, but it's still possible to calculate an Ethernet MAC address. This MAC address can only be used with an external interface such as a SPI-Ethernet device, see /api-reference/network/esp_eth.

Custom Base MAC

The default Base MAC is pre-programmed by Espressif in eFuse {IDF_TARGET_BASE_MAC_BLOCK}. To set a custom Base MAC instead, call the function :cppesp_base_mac_addr_set before initializing any network interfaces or calling the :cppesp_read_mac function. The customized MAC address can be stored in any supported storage device (e.g. Flash, NVS, etc).

The custom base MAC addresses should be allocated such that derived MAC addresses will not overlap. Configure the option CONFIG_{IDF_TARGET_CFG_PREFIX}_UNIVERSAL_MAC_ADDRESSES to set the number of valid universal MAC addresses that can be derived from the custom base MAC, according to the table above.

Note

It is also possible to call the function :cppesp_netif_set_mac to set the specific MAC used by a network interface, after network initialization. It's recommended to use the Base MAC approach documented here instead, to avoid the possibility of the original MAC address briefly appearing on the network before it is changed.

Custom MAC address in eFuse

When reading custom MAC addresses from eFuse, ESP-IDF provides a helper function :cppesp_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:

esp32

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.

not esp32

Field # of bits Range of bits
MAC address 48 200:248

Note

The eFuse BLK3 uses RS-coding during a burn operation it means that all eFuse fields in this block must be burnt at the same time.

Once MAC address has been obtained using :cppesp_efuse_mac_get_custom, call :cppesp_base_mac_addr_set to set this MAC address as base MAC address.

Local vs Universal MAC addresses

{IDF_TARGET_NAME} comes pre-programmed with enough valid Espressif universally administered MAC addresses for all internal interfaces. The specific calculations to derive an interface's MAC address from the base MAC address is shown in the table above..

When using a custom MAC address scheme, it's possible that not all interfaces can be assigned 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 local and universally administered MAC addresses.

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

  1. The U/L bit (bit value 0x2) is set in the first octet of the universal MAC address, creating a local MAC address.
  2. If this bit is already set in the supplied universal MAC address (meaning: 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

:cppesp_chip_info function fills :cppesp_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

:cppesp_get_idf_version returns a string describing the IDF version which was 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 IDF version.

  • :cESP_IDF_VERSION_MAJOR, :cESP_IDF_VERSION_MINOR, :cESP_IDF_VERSION_PATCH are defined to integers representing major, minor, and patch version.

  • :cESP_IDF_VERSION_VAL and :cESP_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 IDF v4.0
#endif

App version

Application version is stored in :cppesp_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 :cppesp_image_header_t and :cppesp_image_segment_header_t structures. The field version has string type and max length 32 chars.

To set version in your project manually you need to set PROJECT_VER variable in your project CMakeLists.txt/Makefile:

  • In application CMakeLists.txt put set(PROJECT_VER "0.1.0.1") before including project.cmake.

(For legacy GNU Make build system: in application Makefile put PROJECT_VER = "0.1.0.1" before including project.mk.)

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

API Reference

inc/esp_system.inc

inc/esp_idf_version.inc