Ublox XPLR-AOA User manual

UBX-21004616 - R02
C1 - Public www.u-blox.com
XPLR-AOA explorer kits
Bluetooth indoor direction finding
User guide
Abstract
This document describes the XPLR-AOA explorer kits for evaluating Bluetooth 5.1 direction finding
and indoor positioning use cases using Angle-of-Arrival methodology. It serves as a practical guide
that explains how the u-blox modules and software included in the kit are used to explore direction-
finding tags and anchor nodes. The kit contents, setup, configuration, and operation are described.

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Document information
Title
XPLR-AOA explorer kits
Subtitle
Bluetooth indoor direction finding
Document type
User guide
Document number
UBX-21004616
Revision and date
R02
28-Jun-2021
Disclosure restriction
C1 - Public
This document applies to the following products:
Product name
NINA-B4
XPLR-AOA-1
XPLR-AOA-2
u-blox or third parties may hold intellectual property rights in the products, names, logos and designs included in this
document. Copying, reproduction, modification or disclosure to third parties of this document or any part thereof is only
permitted with the express written permission of u-blox.
The information contained herein is provided “as is” and u-blox assumes no liability for its use. No warranty, either express or
implied, is given, including but not limited to, with respect to the accuracy, correctness, reliability and fitness for a particular
purpose of the information. This document may be revised by u-blox at any time without notice. For the most recent
documents, visit www.u-blox.com.
Copyright © u-blox AG.

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Contents
Document information .............................................................................................................................2
Contents .......................................................................................................................................................3
1Product description............................................................................................................................5
1.1 Kit includes...................................................................................................................................................6
1.2 Evaluation software....................................................................................................................................6
1.3 System requirements ................................................................................................................................6
2Bluetooth direction finding ..............................................................................................................7
2.1 Technology ...................................................................................................................................................7
2.1.1 Angle of Arrival (AoA).........................................................................................................................7
2.1.2 Angle of Departure (AoD) ..................................................................................................................8
2.1.3 Angles of measurement....................................................................................................................8
3XPLR-AOA anchor nodes and tags ................................................................................................9
3.1 Introduction..................................................................................................................................................9
3.2 Overview........................................................................................................................................................9
3.3 C211 anchor nodes...................................................................................................................................10
3.3.1 Overview .............................................................................................................................................10
3.3.2 Connectors.........................................................................................................................................10
3.3.3 Flashing ..............................................................................................................................................13
3.3.4 Configuring the board......................................................................................................................14
3.4 C209 tags ...................................................................................................................................................14
3.4.1 Overview .............................................................................................................................................14
3.4.2 Software and flashing......................................................................................................................16
4System setup .................................................................................................................................... 17
4.1 Anchor node configuration......................................................................................................................17
4.2 Tag configuration......................................................................................................................................17
4.2.1 Configuring advertising interval....................................................................................................17
4.2.2 Enabling/disabling advertising ......................................................................................................18
4.3 Restore Eddystone Instance ID..............................................................................................................18
5Running system................................................................................................................................ 19
Appendix .................................................................................................................................................... 20
AAnchor node AT commands .......................................................................................................... 20
A.1 Direction finding enable +UDFENABLE................................................................................................20
A.1.1 Description.........................................................................................................................................20
A.1.2 Syntax .................................................................................................................................................20
A.1.3 Defined values ...................................................................................................................................20
A.2 Direction finding filter +UDFFILT ..........................................................................................................20
A.2.1 Description.........................................................................................................................................20
A.2.2 Syntax .................................................................................................................................................20
A.2.3 Defined values ...................................................................................................................................21
A.2.4 Notes ...................................................................................................................................................21

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A.3 Configure direction finding +UDFCFG ..................................................................................................21
A.3.1 Description.........................................................................................................................................21
A.3.2 Syntax .................................................................................................................................................21
A.3.3 Defined values ...................................................................................................................................22
A.4 Angle calculation event +UUDF..............................................................................................................23
A.4.1 Description.........................................................................................................................................23
A.4.2 Syntax .................................................................................................................................................23
A.4.3 Defined values ...................................................................................................................................23
A.5 Other supported AT commands ............................................................................................................23
BGlossary .............................................................................................................................................. 24
CLimitations......................................................................................................................................... 24
DC209 schematics.............................................................................................................................. 25
Related documentation......................................................................................................................... 26
Revision history ....................................................................................................................................... 27
Contact....................................................................................................................................................... 28

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1Product description
A Bluetooth "tag" is a small, thin device that can attached to any object to track its whereabouts. An
"anchor node" calculates the position of the tag. Bluetooth tags can attach to keys, wallets, purses,
and other personal property.
u-blox direction finding solutions that leverage this Bluetooth direction finding technology can be
evaluated using two separate explorer kits, as described in Table 1.
Model
Order code
Description
XPLR-AOA-1
XPLR-AOA-1
Bluetooth 5.1 direction finding explorer kit for evaluating Bluetooth 5.1 direction
finding using Angle-of-Arrival methodology. The kit includes a single C211
application board and one C209 tag:
•C211 application boards include a NINA-B411 module and an antenna array that
represents the anchor node for direction finding, using Angle-of-Arrival
methodology. u-connectLocate direction finding software installed on
NINA-B411 delivers angle information for tracked tags to a listening host.
•C209 tags are based on the open CPU NINA-B406 module variant. The tags run
on custom tag software that advertise Eddystone beacons with appended with
Constant Tone Extensions (CTE). The CTE data is used by C211 application
board to calculate the position of the C209 tag.
XPLR-AOA-2
XPLR-AOA-2
Bluetooth 5.1 direction finding explorer kit for evaluating and developing indoor
positioning use cases, using Angle-of-Arrival methodology. The kit includes a four
C211 application boards, four C209 tags and positioning engine client software:
•C211 application boards include a NINA-B411 module and an antenna array that
represents the anchor node for direction finding using Angle-of-Arrival
methodology. u-connectLocate direction finding software installed on
NINA-B411 delivers angle information for tracked tags to a listening host.
•C209 tags are based on the open CPU NINA-B406 module variant. The tags run
on custom tag software that advertise Eddystone beacons with appended with
Constant Tone Extensions (CTE). The CTE data is used by C211 application
board to calculate the position of the C209 tag.
Table 1: u-blox direction-finding explorer kits and ordering codes
☞For further information about the positioning engine client software for Windows, see also the
indoor positioning guide [2] .
Figure 1: u-blox direction-finding explorer kits comprising C211 application board(s) and C209 tag(s)

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1.1 Kit includes
XPLR-AOA-1 direction finding explorer kit for out-of-the-box AoA evaluation includes:
•C211 antenna board with NINA-B411 Bluetooth LE module
•C209 tag with NINA-B406 Bluetooth LE module
•u-connectLocate direction finding software (from u-blox.com)
•C209 tag software example (from Github)
XPLR-AOA-2 indoor positioning explorer kit for out-of-the-box evaluation of indoor positioning
includes:
•Four C211 antenna boards with NINA-B411 module
•Four C209 tags with NINA-B406 module
•u-connectLocate direction finding software (from u-blox.com)
•C209 tag software example (from Github)
•Positioning engine software example to run on a PC
1.2 Evaluation software
Several evaluation packages are available:
•u-connectLocate delivers angle information for tracked tags to a listening host.
Customers install u-connectLocate software on the NINA B411 module mounted on the C211
integration board. C211 integration boards are delivered with bootloader software only.
•s-center software Bluetooth and Wi-Fi evaluation software provides a powerful and easy-to-use
tool for evaluating, configuring, and testing u-blox short range modules
•Sample positioning-engine client that runs on a local Windows workstation (XPLR-AOA-2 only)
1.3 System requirements
•PC with USB interface
•Operating system: Windows 7 onwards

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2Bluetooth direction finding
Bluetooth direction finding provides a relatively inexpensive and flexible approach to developing
location-related applications for both in indoor and outdoor environments.
Examples of applications for which Bluetooth direction finding technology is most suitable include:
•Asset tracking
•Navigation
•Wayfinding
•Proximity/Direction detection
2.1 Technology
Bluetooth direction finding can be implemented using two different methods, Angle of Arrival (AoA)
and of Departure (AoD).
In each case, protocol-specific control information and user data, transmitted as Bluetooth Protocol
Data Units (PDU), are appended with direction-finding data known as Constant Tone Extension (CTE).
This additional direction-finding data is appended to the end of the packages, as shown in Figure 2.
Figure 2: Bluetooth PDU with Constant Tone Extension
2.1.1 Angle of Arrival (AoA)
In AoA systems, the receiver has an antenna array with multiple antennas. The receiver calculates
the phase shift between these antennas to detect the direction of the tag that it is tracking. An
overview of a system using this method of direction finding is shown in Figure 3.
Figure 3: Angle of Arrival (AoA) system architecture

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2.1.2 Angle of Departure (AoD)
In AoD systems, the transmitter has multiple antennas. The receiver calculates the phase difference
between these antennas to determine the direction to the transmitter. By using this data in
combination with angle data from other transmitters, the receiver can estimate its position. An
overview of a system using this method of direction finding is shown in in Figure 4.
Figure 4: Angle of Departure (AoD) system architecture
2.1.3 Angles of measurement
In both AoA and AoD systems, the reported angles of the azimuth and elevation measurements are
compared against a reference plane, as shown in Figure 5.
Figure 5: Azimuth and elevation angles
For further information about Bluetooth direction finding, see the u-blox webinar “Bluetooth for High
Precision Indoor Positioning” available on the u-blox webinar page [8] and Bluetooth SIG technical
overview [1].

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3XPLR-AOA anchor nodes and tags
3.1 Introduction
Both XPLR-AOA-1 and XPLR-AOA-2 explorer kits include both Bluetooth anchor nodes and tags.
☞Although this chapter generally describes these nodes and tags in the context of the XPLR-AOA-1
direction finding system, the concepts it describes are equally applicable to the XPLR-AOA-2
indoor positioning explorer kit. For information about the XPLR-AOA-2 positioning engine, setup,
and configuration, see also the indoor positioning application note [2].
3.2 Overview
u-blox direction finding solutions are comprised of C211 anchor nodes C209 tags, as shown in Figure
6. See also Kit includes. u-blox direction-finding solution supports the Angle of Arrival (AoA)
methodology.
C211 anchor nodes are based on NINA-B4 modules that include support for direction finding.
Anchor nodes are based on NINA-B411 u-connectXpress functionality, whereas C209 tags are based
on NINA-B406 open CPU architecture. For more information about these short-range Bluetooth
modules, see also the respective data sheets [13][14] and product pages [2].
Figure 6 shows several anchor nodes and a host that uses the combined information from the anchor
nodes to calculate the position of the tag. For simple direction finding one anchor node is sufficient.
Figure 6: XPLR-AOA direction-finding solution showing four anchor points tracking a single tag

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3.3 C211 anchor nodes
3.3.1 Overview
C211 application boards are equipped with a NINA-B411 module and an antenna array. These boards
fulfill the role of the anchor node in the XPLR-AOA direction-finding solutions. Anchor nodes run AT
command-based u-connectLocate direction finding software, which delivers AoA data for tracked
beacons to a listening host. Data is transmitted to the host as events over the NINA-B411 UART
interface. See also Anchor node AT commands.
•C211 has an array of five antennas that are used to detect the phase shift for the direction finding
–in both horizontal and vertical levels.
•C211 also has an LED array in the form of a cross. The LEDs indicate the direction of tracked
beacons. In instances where the anchor node tracks several beacons, the LED array tracks the
first C209 tag that is discovered.
Figure 7: C211 antenna side
The C211 board dimensions are 115 (h) x 114 (w) mm.
3.3.2 Connectors
3.3.2.1 UART
The UART connection must be configured for USB connection with jumpers connecting pins 3 to 5
and 4 to 6 on connector J5, as shown in Figure 8.
Figure 8: Jumper settings for UART connection over USB

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3.3.2.2 Arduino interface
C211 boards contain an Arduino compatible interface that can be used to connect, for example, an
ODIN-W2 EVK to enable wireless communication over UDP. For further information about UDP, see
the u-connectXpress software user guide [16].
The Arduino connectors, J1, J3 and J4, are shown in Figure 9.
Figure 9: C211 with Arduino connectors marked
3.3.2.2.1 Pinout
The pinout of the Arduino compatible connectors is described in EVK-ODIN-W2 wireless gateway
configuration.
Connector
Pin
Name
Description
J1
1
NC
Not connected
2
IOREF
IO reference voltage
3
RESET
Reset
4
3V3
Regulated 3.3 V net. This net is supplied by the board and is always powered as long as a
power source is connected.
5
5V0
5 V supply
6
GND
Ground
7
GND
Ground
8
VIN
External power supply via ODIN-W2
J3
1
NC
Not connected
2
NC
Not connected
3
RXD
Can be connected to NINA-B411 GPIO_22/UART_TXD by populating jumper J5 pin [1-3]
4
NC
Not connected
5
NC
Not connected
6
D5
Not Connected. Can be connected to NINA-B411 GPIO_32 by populating position R68.
7
NC
Not connected

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Connector
Pin
Name
Description
8
NC
Not connected
J4
1
TXD/D8
Can be connected to NINA-B411 GPIO_23/UART_RXD by populating jumper J5 pin [2-4]
Not Connected. Can be connected to NINA-B411 GPIO_33 by populating position R70.
2
D9
Not Connected. Can be connected to NINA-B411 GPIO_46 by populating position R69.
3
NC
Not connected
4
NC
Not connected
5
NC
Not connected
6
D13
Not Connected. Can be connected to NINA-B411 GPIO_45 by populating position R67
7
GND
Ground
8
NC
Not connected
9
SDA
Not Connected. Can be connected to NINA-B411 GPIO_4/I2C SDA by populating position R66.
10
SCL
Not Connected. Can be connected to NINA-B411 GPIO_5/I2C SDL by populating position R65.
Table 2: Pin out of Arduino connectors
3.3.2.2.2 Connecting EVK-ODIN-W2 for wireless communication
When connecting an EVK-ODIN-W2 evaluation kit for wireless communication, you need to redirect
the TX channel from the C211 anchor to EKV-ODIN-W2 by modifying the jumpers on the J5 connector,
as shown in Figure 10. This connects the UART TX pin on the C211 to UART1 RX on the EVK-ODIN-
W2. See also the EVK-ODIN-W2 user guide [15].
Figure 10: Redirecting C211 UART TX to Arduino connector
3.3.2.2.3 Power supply
When mounting an ODIN-W2 EVK, the application board is powered through the ODIN-W2 EVK USB
contact. No other power supply to the C211 board is needed.
3.3.2.3 EVK-ODIN-W2 wireless gateway configuration
For C211 wireless communication though an EVK-ODIN-W2, the EVK must first be configured as a
wireless UDP gateway. In this configuration the EVK can:
•Connect to a Wi-Fi network
•Automatically connect to the UDP server at “server_ip” and “udp_port”
•Startup in data mode
•Set the UART to 1 Mbps with no flow control

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1. Enter the following commands to setup EVK-ODIN-W2 as a wireless UDP gateway:
☞Replace “ssid”, “password” and “server_ip” and “udp_port” with suitable values for your network.
AT+UWSC=0,0,1
AT+UWSC=0,2,"ssid"
AT+UWSC=0,5,2
AT+UWSC=0,8,"password"
AT+UWSC=0,100,2
AT+UWSC=0,107,0
AT+UWSC=0,300,0
AT+UWSC=0,301,1
AT+UWSCA=0,1
AT+UWSCA=0,3
AT+UDDRP=0,"udp://server_ip:udp_port/",2
AT+UMSM=1
AT+UMRS=1000000,2,8,1,1,0
AT&W
AT+CPWROFF
2. After the configuration it is also necessary to remove the J13 and J22 jumpers on the
EVK-ODIN-W2 that selects UART1/UART3, as shown in Figure 12. This directs the UART signals
to the Arduino-compatible interface.
Figure 11: UART selection jumpers to be removed on ODIN-W2 EVK
3. On C211, set the UART baud rate and other interface settings to 1 Mbps, with no flow control:
AT+UMRS=1000000,2,8,1,1,0
AT&W
AT+CPWROFF
3.3.3 Flashing
Other than the bootloader, C211 boards are delivered without software.
Follow the procedure outlined below to flash the board over the UART connection.
1. Download the u-connectLocate software container from www.u-blox.com
The Newt manager flashing tool (newtmgr) used to install u-connectLocate software is included in
the u-connectLocate download container. The tool can also be retrieved from the mynewt
download site [10]. See also the Newt Manager Guide [10].
2. Use Newt Manager to install u-connectLocate on the NINA-B411 module:
newtmgr --conntype=serial --connstring="COMXX,baud=115200" image upload <binary image>

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3. Press the reset button to reset the application board or reset it with newtmgr:
newtmgr --conntype=serial --connstring="COMXX,baud=115200" reset
☞As there is no software to boot during the initial startup, the NINA-B411 module automatically
enters the software download mode For future updates of NINA-B41 u-connectLocate software
the bootloader must be manually set in software upload mode by pressing the SW2 button while
resetting the board.
3.3.4 Configuring the board
When connecting to the USB port on the C211, a serial port (COM port on Windows) is available on
the host. Connect the COM port to a terminal emulator or use the s-center tool [7] to initially configure
the port settings:
•115200 kbps
•8 data bits, no parity, 1 stop bit (8N1)
•Flow control enabled using RTS/CTS
Having configured the COM port, configure the C211 using AT commands. The appropriate AT
commands for configuring direction finding through the C211 anchor nodes are described in
Appendix A.
☞Although s-center does not support specific direction-finding AT commands using buttons, it is
possible to configure the COM port as a terminal for use with AT commands.
Due to the large amount of data received over the UART it may be advisable to increase the baud rate
over the UART interface. In the following command example the baud rate is set to 1 Mbps using the
command AT+UMRS.
AT+UMRS=1000000,1,8,1,1,1
For further information command AT+UMRS, see also the u-connectXpress AT command manual [5].
3.4 C209 tags
3.4.1 Overview
C209 tags are based on the open CPU NINA-B406 module variant. The tags run on custom tag
software that advertises as an Eddystone beacon with a Constant Tone Extension added to the
advertising packets. This CTE is used by the u-connectLocate direction finding software that runs on
the C211 application board to calculate the Angle of Arrival.
The namespace included in the transmitted Eddystone-UID beacon is 0x4E494E412D4234544147 and
the instance id is based on the MAC address of the NINA-B406 found on the module QR code label.
See also Restore Eddystone Instance ID.
C209 tags are powered by a single CR2032 battery (not included) or through the USB connector.
C209 tags includes a versatile sensor node that comprises several sensors for use in a multitude of
different applications. The on-board sensors include:
•LIS2DW12 accelerometer
•APDS-9306 ambient light sensor
•BME280 humidity, pressure, and temperature sensor

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The main components of any C209 tag are shown in Figure 12.
Figure 12: C209 main functional components
The important pin definitions on the C209 application board are described in Table 3.
No.
Name
I/O
Description
Remarks
GPIO_1
RED
O
RED system status signal
Active low
GPIO_2
LIS_INT
I
Interrupt signal from Ambient Light
Sensor
GPIO_7
GREEN
O
GREEN system status signal
Active low
GPIO_8
BLUE
O
BLUE system status signal
Active low
GPIO_18
SWITCH_2
I
Switch_2 button
Active low
GPIO_20
UART_RTS
O
UART request to send control signal
Used only when hardware flow control is enabled
GPIO_21
UART_CTS
I
UART clear to send control signal
Used only when hardware flow control is enabled
GPIO_22
UART_TXD
O
UART data output
GPIO_23
UART_RXD
I
UART data input
GPIO_42
LIS_INT
I
Interrupt signal from accelerometer
Table 3 Important pin definitions on the C209
For more information about programming the module, see also the NINA-B4 system integration
manual [6] and NINA-B40 data sheet [13]. See also C209 schematics.
☞Although the sensors on the C209 application board are not used in the latest direction-finding
tag software from u-blox, the sensors can be utilized in any customer application.

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3.4.2 Software and flashing
C209 tags are delivered with bootloader software only and do not include the tag software (from
Github) needed for the device to advertise Bluetooth beacons to C211 anchor nodes.
The bootloader on C209 tags is different than that supplied on C211anchor nodes, and the nrfutil [11]
flashing tool is needed to install the open-source tag software (from Github). C209 tag software is
available from the u-blox open CPU repository [12].
Flash C209 using the following command:
☞Replace COMXX with the appropriate COM port for your system.
nrfutil dfu serial -pkg app.zip -p COMXX -b 115200 -fc 1
The bootloader needs to be manually set in the software “upload”mode by pressing the SW2 button
(see Figure 13) on the C209 while resetting the board.
The C209 can also be flashed using a debugger, using the 10-pin debugger contact available on the
PCB.

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4System setup
4.1 Anchor node configuration
By default, the C211 Anchor Point comes pre-configured to track all u-blox tags. The u-blox tags
advertise with the Eddystone namespace 0x4E494E412D4234544147,which is default on the C211 to
track. So, if you are only using the u-blox supplied XPLR-AOA kit, no configuration is needed.
Each anchor node can be configured with beacons to track. An example for how to set up the anchor
to track two tags is shown below:
AT+UDFFILT=2,2,”6E616D65737061636578”
At+UDFFILT=1,2,“CCF9578E0D8A”,”CCF9578E0D8B”
AT+UDFENABLE=1 (Tracking is enabled by default, so this is optional)
These commands set up the anchor to track the two tags with the given MAC addresses in the
Eddystone name space (6E616D65737061636578) used by the tags.
The sequence described above reflects the most simplistic use case. Further configuration is possible
using the AT+UDFCFG command. See also Configuration direction finding +UDFCFG.
The settings shall be saved using the AT&W command, followed by a restart (AT+CPWROFF).
4.2 Tag configuration
4.2.1 Configuring advertising interval
Press the SW2 button on the C209 to change the advertising interval. The default interval at startup
is 20 milliseconds
When SW2 is pressed, the advertising interval cycles through [20, 100, 1000] milliseconds. For best
performance, it is advisable to use the default 20 ms advertising interval.
Figure 13: C209 with cover and SWITCH_2 marked

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C209 tags are simply configured over the UART interface using AT commands.
The AT commands that can be used to configure the interface are described in Table 4.
Command
Description
AT+UMLA=1
Read Local MAC address
AT+GMM
Read the model identifier, will be NINA-B4-TAG
AT+TXPWR=<valid_tx_power>
<valid_tx_power> can be one of: -40, -30, -20, -16, -12, -8, -4, 0, 2, 3, 4, 5, 6, 7, 8 (dBm)
Table 4 C209 AT commands
☞For +TXPWR to take effect the software must be reset, by pressing the reset button or power cycling
the module. The configuration is persistently stored in flash.
All commands are echoed and responded with either \r\nOK\r\n or \r\nERROR\r\n, and should be
terminated with \r.
☞The UART interface is available for 10 seconds after reset with the settings 115200 bps, with no
flow control.
4.2.2 Enabling/disabling advertising
Press and hold the C209 button for ~3 seconds to enable/disable advertising. If the tag is advertising,
press and hold the button to stop it advertising. The onboard RGB LED blinks blue when advertising
is enabled. The blinking interval correlates to the advertising interval.
4.3 Restore Eddystone Instance ID
All u-blox modules are delivered with a u-blox MAC address, which is written into the UICR register.
If the MAC address is accidentally erased, for example during a reflash of the software, this
information is lost. If this happens, the Eddystone Instance ID transmitted in the C209 advertising
beacon will not match the MAC address of the module. To correct this:
4. Scan the QR code on the module label. The information in the code includes a code that includes
the MAC address (shown here in bold): H85(CCF9578E0D89)0400.
5. Enter these commands to reinstate the MAC address CCF9578E0D89 into the UICR of the
module:
nrfjprog --memwr 0x10001080 --val 0x8E57F9CC
nrfjprog --memwr 0x10001084 --val 0xFFFF890D
Another example for which the MAC address given in the scan code is 0123456789AB:
nrfjprog --memwr 0x10001080 --val 0x67452301
nrfjprog --memwr 0x10001084 --val 0xFFFFAB89
6. After writing the MAC address, reset the module. The module now transmits the correct
Eddystone Instance ID for the C209 tag.

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5Running system
Once the system is setup, each anchor reports, over the serial port connection, angle calculation
events (+UUDF) when it detects a beacon:
+UUDF: CCF9578E0D8A,-42,20,0,-43,37,”CCF9578E0D89”,””,15869
+UUDF: CCF9578E0D8B,-41,10,4,-42,38,”CCF9578E0D89”,””,15892
+UUDF: CCF9578E0D8A,-42,-10,2,-43,39,”CCF9578E0D89”,””,15921
…
The data reported in this event can be used to estimate a position of the tracked beacon.
The parameters of the +UUDF event are (in order from left to right):
•Eddystone instance ID
•RSSI of 1st polarization
•Azimuth angle
•Elevation angle
•RSSI of 2nd polarization
•The advertising channel where the advertisement was found. The advertisement channel is one of
the normal Bluetooth low energy advertisement channels (37, 38 or 39)
•Anchor ID as set by AT+UDFCFG tag 4 (see appendix A.3 for more details)
•User defined strings as set by AT+UDFCFG tag 2. For more details. See also Configure direction
finding +UDFCFG.
•Timestamp
For a detailed description of the +UUDF event parameters, see also Angle calculation event +UUDF.
As can be seen in the angle calculation events shown above, the beacon is moving from one side of
the anchor to the other, as the azimuth angle, given as the third parameter in the command (shown
in bold), moves from a positive value (20) to a negative value (-10). The geometric relationships of
these azimuth values are represented in the scientific diagram shown in Figure 13.
Figure 14 C211 azimuth angles

UBX-21004616 - R02 Appendix Page 20 of 28
C1 - Public
Appendix
AAnchor node AT commands
A.1 Direction finding enable +UDFENABLE
+UDFENABLE
Modules
NINA-B41X-40B
Attributes
Syntax
Settings saved
Can be aborted
Response time
Full
No
No
-
A.1.1 Description
AT Command
Description
AT+UDFENABLE=<enabled>
Start or stop angle calculations during runtime
A.1.2 Syntax
Response
Description
OK
Successful write response
ERROR
Error Response
A.1.3 Defined values
Parameter
Type
Description
Enabled
Integer
0: Disabled
1: Enabled
A.2 Direction finding filter +UDFFILT
+UDFFILT
Modules
NINA-B41X-40B
Attributes
Syntax
Settings saved
Can be aborted
Response time
Full
Yes
No
-
A.2.1 Description
Configure a filter to decide which tags to track. This command is used to configure the filter to either
track all devices with a specific namespace, or individual tags with a certain namespace and instance
id. Currently, only filter types 1,2 (EDDYSTONE) are supported.
AT command
Description
AT+UDFFILT=<filter_type>,<action>[,<option_val1>
,<option_val2>,…<option_valXX>]]]
Set the tag filter for tracked tags
AT+UDFFILT=<filter_type>
Read the current filter for the specified
<filter_type>
A.2.2 Syntax
Response
Description
+UDFFILT:<filter_type>,<option_val1>,..
OK
Read response
OK
Successful write response
Error
Error response