esp-idf/examples/system/base_mac_address

Base MAC Address

(See the README.md file in the upper level 'examples' directory for more information about examples.)

Each network interface on the ESP32 (e.g., WiFi Station/AP, BT, Ethernet) must be assigned a unique Medium Access Control (MAC) address. Each interface's MAC address is derived from a base MAC address that must be set before any network interface's initialization is called.

This example demonstrates the following:

1. How to retrieve a base MAC address from non-volatile memory
2. How to set the base MAC address
3. How to obtain the derived MAC addresses of each network interface

This example utilizes the MAC Address API.

How to use example

Hardware Required

This example should be able to run on any commonly available ESP32 development board. However, if an external source of non-volatile memory is used to store the base MAC address (e.g. an I2C Serial EEPROM), the user should wire the connections to their chosen external storage as needed.

Configure the project

idf.py menuconfig

• To select the storage source of the base MAC address, go to Example Configuration > Storage location of the base MAC address where the following options are available:

  • eFuse BLK0 will cause this example to read the base MAC address from eFuse Block 0 and is selected by default. The eFuse BLK0 MAC address is factory programmed into each ESP32.
  • eFuse BLK3 will cause this example to read the base MAC address from words 1 & 2 of eFuse Block 3. eFuse BLK3 allows users to use a custom eFuse, but must be burned into the ESP32 using the espefuse tool. Attempting to read eFuse BLK3 without burning the eFuse will result in an error.
  • Other external storage will call a external_storage_mac_get() which will merely retrieve an arbitrary base MAC address that is set in software. Users should re-implement external_storage_mac_get() to access their chosen external storage (e.g. an I2C Serial EEPROM)

• If eFuse BLK3 is chosen, the Behavior when retrieving BLK3 eFuse fails option may also be selected. When retrieving the base MAC address from eFuse BLK3 without burning eFuse Block 3, the example can either abort or default to retrieving from eFuse Block 0.

Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

idf.py -p PORT flash monitor

(Replace PORT with the name of the serial port to use.)

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Example Output

Depending on the Storage of the base MAC address configuration option, the console should output one of the following logs to indicate the source of the base MAC address.

I (288) BASE_MAC: Base MAC Address read from EFUSE BLK0
...
I (288) BASE_MAC: Base MAC Address read from EFUSE BLK3
...
I (288) BASE_MAC: Base MAC Address read from external storage

The console will also output the retrieved 6 byte MAC address when it sets it as the system wide base MAC address.

I (298) BASE_MAC: Using "0xd8, 0xa0, 0x1d, 0x0, 0xb, 0x88" as base MAC address

The console will then output the derived MAC address of each network interface as such:

I (297) WIFI_STA MAC: 0x0, 0x11, 0x22, 0x33, 0x44, 0x55
I (307) SoftAP MAC: 0x0, 0x11, 0x22, 0x33, 0x44, 0x56
I (317) BT MAC: 0x0, 0x11, 0x22, 0x33, 0x44, 0x57
I (317) Ethernet MAC: 0x0, 0x11, 0x22, 0x33, 0x44, 0x58

Troubleshooting

When attempting to retrieve the base MAC address from eFuse BLK3 without first burning eFuse Block 3 will result in one of the following situations.

If the example has been configured to abort when retrieving from eFuse BLK3 fails.

E (288) system_api: Base MAC address from BLK3 of EFUSE version error, version = 0
E (298) BASE_MAC: Failed to get base MAC address from EFUSE BLK3. (ESP_ERR_INVALID_VERSION)
E (308) BASE_MAC: Aborting
abort() was called at PC 0x400d237b on core 0

If not configured to abort, the example will default to eFuse BLK0 and output the following instead.

E (288) system_api: Base MAC address from BLK3 of EFUSE version error, version = 0
E (298) BASE_MAC: Failed to get base MAC address from EFUSE BLK3. (ESP_ERR_INVALID_VERSION)
I (308) BASE_MAC: Defaulting to base MAC address in BLK0 of EFUSE
I (308) BASE_MAC: Base MAC Address read from EFUSE BLK0