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