s

nRF52832 change mac address


2 Target

I need multi beacons with multi ble macs in a same nRF52832 PCA10040 board.

3 Introduce the bluetooth mac

check the detail in bluetooth specification version 5.0

vol 6, part B, 1.3
vol 2, part B, 1.2

3.1 device address

Devices are identified using a device address. Device addresses may be either
a public device address or a random device address. A public device address
and a random device address are both 48 bits in length.

A device shall use at least one type of device address and may contain both.

A device's Identity Address is a Public Device Address or Random Static Device
Address that it uses in packets it transmits. If a device is using Resolvable
Private Addresses, it shall also have an Identity Address.

3.1.1 public device address

Each bluetooth device shall be allocated a unique 48-bit Bluetooth device
address (BD_ADDR). The address shall be a 48-bit extended unique identifier
(EUI-48).
Notice that you have to obtain a MAC address range from the IEEE registration
Authority if you want to use public address for your devices.

3.1.2 random device address

The random device address may be of either of the following two sub-types:

  • static address
  • private address
  1. static address

    A static address is a 48-bit randomly generated address and shall meet the
    following requirements:

    • The two most significant bits of the address shall be equqal to 1
    • At least one bit of the random part of the address shall be 0
    • At least one bit of the random part of the address shall be 1

    Note: If the static address of a device is changed, then the address stored
    in peer devices will not be valid and the ability to reconnect using the old
    address will be lost.

  2. private device address

    The private address may be of either of the following two sub-types:

    • Non-resolvable private address
    • Resolvable private address

    To generate a non-resolvable address, the device shall generate a 48-bit address
    with the following requirements:

    • The two most significant bits of the address shall be equqal to 0
    • At least one bit of the random part of the address shall be 0
    • At least one bit of the random part of the address shall be 1
    • The address shall not be euqal to the public address

    To generate a resolvable private address, the device must have either the
    Local Identity Resolving Key (IRK) or the Peer Identity Resolving Key (IRK).
    The resolvable private address shall be generated with the IRK and a randomly
    generated 24-bit number. The random number is known as prand and shall meet the
    following requirements:

    • The two most significant bits of prand shall be equqal to 0 and 1
    • At least one bit of the random part of prand shall be 0
    • At least one bit of the random part of prand shall be 1
    • The address shall not be euqal to the public address

4 the tests with nRF52832

the test board is PCA10040 with nRF52832.
SDK version: nRF5_SDK_14.2.0

Use the api `sd_ble_gap_addr_set' to set address, the address type as below:

#define BLE_GAP_ADDR_TYPE_PUBLIC                        0x00 /**< Public address. */
#define BLE_GAP_ADDR_TYPE_RANDOM_STATIC                 0x01 /**< Random static address. */
#define BLE_GAP_ADDR_TYPE_RANDOM_PRIVATE_RESOLVABLE     0x02 /**< Random private resolvable address. */
#define BLE_GAP_ADDR_TYPE_RANDOM_PRIVATE_NON_RESOLVABLE 0x03 /**< Random private non-resolvable address. */

4.1 change mac to be public address

set code as below:

ble_gap_addr_t gap_address;
gap_address.addr_type = BLE_GAP_ADDR_TYPE_PUBLIC;
memcpy(&gap_address.addr, "\x62\x52\x42\x09\xe7\x34", sizeof(gap_address.addr));
err_code = sd_ble_gap_addr_set(&gap_address);
APP_ERROR_CHECK(err_code);

4.2 change mac to be random static address

make sure the The two most significant bits of the address shall be equqal to 1.
The code below change the two most significatn bits to be 1.

gap_address.addr[5] |= 0xc0;

set code as below for a random static mac:

ble_gap_addr_t gap_address;
gap_address.addr_type = BLE_GAP_ADDR_TYPE_RANDOM_STATIC;
memcpy(&gap_address.addr, "\x62\x52\x42\x09\xe7\x34", sizeof(gap_address.addr));
gap_address.addr[5] |= 0xc0;
err_code = sd_ble_gap_addr_set(&gap_address);
APP_ERROR_CHECK(err_code);

4.3 change mac to be random private address

4.3.1 change as random private resolvable address

Reference link below for detail:
https://devzone.nordicsemi.com/question/107812/directed-advertising-with-pre-shared-irk/