How to get 6 byte mac address at nrf51822

[Lee YongKwan]

When I scan BLE device at nRF UARTv2.0 App in Android4.4, it is appar device name(Ex:Nordic_UART) and 6 byte device address(MAC address?). I want to include mac address in device name. How to get 6 byte mac address at nrf51822?

[Håkon Alseth]

By default, the BLE address is derived from the NRF_FICR->DEVICEADDR[] and is of 48 bits length (6 bytes). This registers are randomly generated in our production, and they are unique for each device (2^46 different combinations, due to MSbits set to '11').

You can read out the address using the API call, "sd_ble_gap_address_get(..);" or reading the FICR->DEVICEADDR[x] registers.

Example: My device advertises with "0xE724 08C78790"

DEVICEADDR[0] = 0x08C78790 DEVICEADDR[1] = 0xYYYYA724

The reason why "A7" becomes "E7" is because the specification says that the 2 MSBit of the address must be set '11' (if you're very interested, see Bluetooth Core v4.0, Vol 3, Part C, chapter 10.8.1.)

BR Håkon

[Jakub]

What is the smallest part of MAC address that can be used as a unique ID of a certain device?

I know that first 3 bytes are vendor-specific (Nordic) so another 3 bytes are unique across Nordic products. But are they totally random, or is there any pattern that can allow us to use only 2 bytes for a specific product (nRF51822)?

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Disclaimer: I know this is an old thread, but frequently shows up in Google and that's why I decided to include my question here.