Changing MAC Address in nrf52

[Swapnil]

Hello,

I am trying to change the MAC address of my device nRF52, by using NRF_FICR->DEVICEADDR[0], NRF_FICR->DEVICEADDR[1], I am able to see the device address.

But when I try to change it by using below code it doesn't change, it shows the same address,

p_addr.addr_type = BLE_GAP_ADDR_TYPE_RANDOM_PRIVATE_NON_RESOLVABLE;

for(uint8_t i = 0; i<6; i++)
{
	p_addr.addr[i] = 0xAAAAAAAA;
}

I am calling this in main function. After executing this code when I try to read NRF_FICR->DEVICEADDR[0], NRF_FICR->DEVICEADDR[1], i still see the same previous address.

what would be the problem ?

[Jørgen Holmefjord]

Do you also set the address using sd_ble_gap_addr_set() function? What is the return value? You also need to make sure that the two LSB of the address corresponds to the address type.

[Swapnil]

Yes I am using sd_ble_gap_addr_set(), and i am getting return value of error code: 12802

[Jørgen Holmefjord]

The error code 12802 (0x3202) corresponds to BLE_ERROR_GAP_INVALID_BLE_ADDR. You should make sure the address you enter use the correct format for the address type. You can set the address from FICR like this:

static ble_gap_addr_t m_central_addr;

m_central_addr.addr_type     = BLE_GAP_ADDR_TYPE_RANDOM_STATIC;
m_central_addr.addr[0] = (uint8_t)NRF_FICR->DEVICEADDR[0];
m_central_addr.addr[1] = (uint8_t)(NRF_FICR->DEVICEADDR[0] >> 8);
m_central_addr.addr[2] = (uint8_t)(NRF_FICR->DEVICEADDR[0] >> 16);
m_central_addr.addr[3] = (uint8_t)(NRF_FICR->DEVICEADDR[0] >> 24);
m_central_addr.addr[4] = (uint8_t)NRF_FICR->DEVICEADDR[1];
m_central_addr.addr[5] = (uint8_t)((NRF_FICR->DEVICEADDR[1] >> 8) | 0xC0); // 2MSB must be set 11

sd_ble_gap_addr_set(&m_central_addr);

[Swapnil]

Thank you, yes its working now. Again I have a question, what if I use address type as public address ?

[Jørgen Holmefjord]

If you set the address type to public, you should be able to use any address. 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.