How to read public MAC using the nrfjprog.exe tool?

RE: How to read public MAC using the nrfjprog.exe tool?

ovrebekk — Thu, 16 Apr 2020 09:26:16 GMT

Hi Daniel

The device address bytes stored in the flash are random numbers, and won't necessarily follow the Bluetooth specification requirements for a valid BLE address.

When using a static random BLE address the two most significant bits shall both be 1, which is why 0x8B is changed to 0xCB by the SoftDevice before setting the address.

For more information please refer to the Device Address chapter in the Bluetooth specification (Vol 6, Part B, chapter 1.3 in v5.0 of the specification).

Best regards
Torbjørn

RE: How to read public MAC using the nrfjprog.exe tool?

Daniel — Wed, 15 Apr 2020 18:26:49 GMT

Hi,

When I used the same command, I was only able to read the 5 bytes correctly. The Most higher byte does not match.

C:\Program Files\Nordic Semiconductor\nrf-command-line-tools\bin>nrfjprog --memrd 0x100000A4 --n 8
0x100000A4: 121DCF55 7C1D8BD6 |U......||

From Nrfconnect, I noticed a different mac address.

Am I missing anything?

RE: How to read public MAC using the nrfjprog.exe tool?

ovrebekk — Tue, 09 Oct 2018 09:14:03 GMT

I am glad to hear you figured it out Bon!

As for your question Hugh it would be better to open a new case.
A quick comment though, why is the code snippet using the sd_ble_gap_device_name_set(..) function, while you refer to sd_ble_gap_address_set() in the text?

Best regards
Torbjørn

RE: How to read public MAC using the nrfjprog.exe tool?

bon.chen — Tue, 09 Oct 2018 02:25:35 GMT

Thank you.

Now I can read the public MAC.

RE: How to read public MAC using the nrfjprog.exe tool?

hmolesworth — Mon, 08 Oct 2018 17:28:43 GMT

Hi Torbjørn

For another user on this forum asking a question on the BLE address I tried using the sd_ble_gap_address_set() but found the address did not change even though the return code rcode below was NRF_SUCCESS:

 ble_gap_conn_sec_mode_t myMode = {.sm = 0, .lv = 0};
 uint8_t myName[6] = {0x01,0x02,0x03,0x04,0x05,0xC6};
 // Doesn't allow set if BLE name is in FLASH - maybe see ref sd_ble_cfg_set()
 uint32_t rcode = sd_ble_gap_device_name_set(&myMode, myName, sizeof(myName));

I'm curious as to why the actual BLE address reported remained unchanged. I tried both immediately after ble_stack_init() and later with the same result (success but same ble address). It's not clear where the original ble address variable is located: RAM or Flash? If the latter the return code would have indicated other than success

    db_discovery_init();
    ble_stack_init();
    ReportSignOnString();   // <- Test here
    gatt_init();
    nus_c_init();

    db_discovery_init();
    ble_stack_init();
    gatt_init();
    nus_c_init();
    ReportSignOnString();   // <- Test here

RE: How to read public MAC using the nrfjprog.exe tool?

CheMax — Mon, 08 Oct 2018 11:28:45 GMT

Thank you, for myself, I learned and understood everything.

I hope the author of this issue will also find a solution for himself.

RE: How to read public MAC using the nrfjprog.exe tool?

ovrebekk — Mon, 08 Oct 2018 08:22:47 GMT

Hi CheMax

You can set the BLE address to whatever you like using the sd_ble_gap_address_set(..) function, there is no need to change the DEVICEADDR registers.

In other words you have full flexibility in the app to control the address assignment.

Best regards
Torbjørn

RE: How to read public MAC using the nrfjprog.exe tool?

CheMax — Mon, 08 Oct 2018 07:30:15 GMT

Thanks for the addition.
As far as I understand, if I have my own address, I cannot write it to this area of memory. If this is the case, then why is the address that you provide does not have high bits set?

I really don't understand the reason for this decision.

Thank you,

RE: How to read public MAC using the nrfjprog.exe tool?

ovrebekk — Mon, 08 Oct 2018 07:23:51 GMT

To add to CheMax's reply, you can read DEVICEADDR[0] and DEVICEADDR[1] with the following command:

nrfjprog --memrd 0x100000A4 --n 8

The first register returned will be DEVICEADDR[0], containing bits 31-0 of the BLE address.

The second register is DEVICEADDR[1], from which the higher order bits are copied.

Keep in mind that to get a proper public MAC address you have to register it yourself with the IEEE.
The address provided by DEVICEADDR is a random static address only, and not guaranteed to be unique.

Best regards
Torbjørn

RE: How to read public MAC using the nrfjprog.exe tool?

CheMax — Mon, 08 Oct 2018 06:54:59 GMT

If you look at the "help", you will not see the direct command "Give a Mac"

but you can read the values of the two registers with the factory settings and build the MAC address of the device yourself. It is worth remembering that the two bits of the address (46 and 47) should be one, because the address is random and public.

I think that implementing it in a script language (e.g. batch) is not a difficult task.

Best regards, Max