Configure device address¶
A BLE device needs an address to do just about anything. For information on the various types of Bluetooth addresses, see the NimBLE Host Identity Reference :doc:`<../ble_hs/ble_hs_id/ble_hs_id>.
There are several methods for assigning an address to a NimBLE device. The available options are documented below:
Method 1: Configure nRF hardware with a public address¶
When Mynewt is running on a Nordic nRF platform, the NimBLE controller will attempt to read a public address out of the board’s FICR or UICR registers. The controller uses the following logic while trying to read an address from hardware:
If the DEVICEADDRTYPE FICR register is written, read the address programmed in the DEVICEADDR[0] and DEVICEADDR[1] FICR registers.
Else if the upper 16 bits of the CUSTOMER[1] UICR register are 0, read the address programmed in the CUSTOMER[0] and CUSTOMER[1] UCI registers.
Else, no address available.
Method 2: Hardcode a public address in the Mynewt target¶
The NimBLE controller package exports a
syscfg setting
called BLE_PUBLIC_DEV_ADDR. This setting can be overridden at the
application or target level to configure a public Bluetooth address. For
example, a target can assign the public address 11:22:33:44:55:66 as
follows:
syscfg.vals:
BLE_PUBLIC_DEV_ADDR: '(uint8_t[6]){0x66, 0x55, 0x44, 0x33, 0x22, 0x11}'
This setting takes the form of a C expression. Specifically, the value is a designated initializer expressing a six-byte array. Also note that the bytes are reversed, as an array is inherently little-endian, while addresses are generally expressed in big-endian.
Note: this method takes precedence over method 1. Whatever is written to
the BLE_PUBLIC_DEV_ADDR setting is the address that gets used.
Method 3: Configure a random address at runtime¶
Random addresses get configured through the NimBLE host. The following two functions are used in random address configuration:
ble_hs_id_gen_rnd(): Generates a new random address.ble_hs_id_set_rnd(): Sets the device’s random address.
For an example of how this is done, see the BLE iBeacon.
Note: A NimBLE device can be configured with multiple addresses; at most one of each address type.