How to change the BLE mac address of NRF5430 at Real Time with NCS SDK?

[John]

  I follow below thread and refer to sample code and  the BLE mac address can be changed after system just boot up.

   devzone.nordicsemi.com/.../325131

   But after boot up, I want to change  the BLE mac address again, it doesn't work and the ble MAC address keep unchanged, it is expected?  Is it possible to change the desired BLE mac address at real time without HW reset?

Below is my Sudo code:

nrf5340 boot up,  

bt_enable(NULL);

bt_addr_t addr = {{0xFE, 0xCA, 0xA0, 0xAC, 0xDC, 0xBA}};
ble_set_mac(&addr);

settings_load();

ble_advertise();  //it works with ble addr = {{0xFE, 0xCA, 0xA0, 0xAC, 0xDC, 0xBA}}

ble_Stop_advertise();

bt_addr_t addr = {{0xFE, 0xCA, 0xA0, 0xAC, 0xDC, 0xBB}};
ble_set_mac(&addr);

settings_load();

ble_advertise(); //it doesn't work, ble address cant be changed.

found the ble's mac address is still  = {{0xFE, 0xCA, 0xA0, 0xAC, 0xDC, 0xBA}};

[Karl Ylvisaker]

Hello John,

Do you need to change the address to a specific other address, or just to change it at all (like the privacy feature)?
In case of the latter you could use the sdc_hci_cmd_le_set_random_address function to achieve this.

Or, is your intention to go between 2 specific mac addresses, for instance?

Best regards,
Karl

[John]

Hi Karl, I need to change to specific other address.

[Einar Thorsrud]

It is allowed if you use a random address (resolvable or non-resolvable), but a static address cannot be changed runtime. From the Bluetooth Core specification (Version 5.3 | Vol 6, Part B, 1.3.2.1):

A device may choose to initialize its static address to a new value after each power cycle. A device shall not change its static address value once initialized until the device is power cycled.

So the main thing here should not be if it is possible or not, as it is simply not allowed.

[John]

hi Einar Thorsrud,

  For the Old SDK v16.0.0 wiht nrf52840 we can change BLE's mac address at runtime when ble disconnected and stop broadcasing by below API and parameter:

     addr.addr_id_peer = 0;

     addr.addr_type= 1; 

   sd_ble_gap_addr_set(&addr);

  for NCS SDK say 2.3.0 with nrf5430, are there any API to do so?

   

[Einar Thorsrud]

Yes, you could do it, but it has always been illegal (even in Bluetooth core specification 4.0 where Bluetooth Low Energy was first introduced). I am not aware of any API's that will allow you to do it in recent nRF Connect SDK releases.

[John]

Einar Thorsrud, got it and thanks for your support.

[John]

one more issue....

I use below to change the ble mac address:

bt_addr_le_t addr;
err = bt_addr_le_from_str("FF:EE:DD:CC:BB:AA", "random", &addr);
if (err) {
printk("Invalid BT address (err %d)\n", err);
}

err = bt_id_create(&addr, NULL);
if (err < 0) {
printk("Creating new ID failed (err %d)\n", err);
}

It works, the BLE mac address can be change succesfully. I checked by nrf Connect App -> Scanner.

But after HW reset NRF5430 device, the BLE address is changed be to another BLE mac address, seems it is NRF5430's default/factory mac address.

my question is how to keep my modified BLE Mac address after HW reset/power-up cycle?

[Einar Thorsrud]

It should normally be stored if you have settings enabled. That means having this in your prj.conf:

CONFIG_BT_SETTINGS=y
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_NVS=y
CONFIG_SETTINGS=y

And also calling settings_load() early in your code.

(There was an issue reported where this would not work in a corner case based on priority, but that may not be relevant for you in this case).

[John]

Hi Einar Thorsrud,

I have enabled below setting in proj.conf:

CONFIG_BT_SETTINGS=y
CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FLASH_MAP=y
CONFIG_NVS=y
CONFIG_SETTINGS=y

but still not works..

Calling settings_load() early in your code, means before bt_enable() or just after after  bt_enable()?

[Einar Thorsrud]

You are right, this is not as straight-forward on the nRF5340. For a persistent public address, the best could be to store it for instance in UICR (that way it is easy to program different addresses to different boards during production), and load it at every boot, as suggested in this post.