AoA Tag Sample Application

This repository contains an example Tag application for use with u-blox ANT-B10 and C211 Bluetooth Direction Finding Anchor. It is intended to be flashed on the u-blox C209 Tag which comes with XPLR-AOA-1, XPLR-AOA-2 and XPLR-AOA3 kits. C209 AoA Tag releases from v2.0.0 are compatible with u-connectLoate 2.0 and later.

Getting the code

git clone https://github.com/u-blox/c209-aoa-tag.git

Setup

Below is a short summary of the required steps to compile the application. For more detailed instructions go to the offical nRF Connect Getting Started Guide

Download nRF Connect and Toolchain

• Open nRF Connect for Desktop and open the Toolchain Manager.
• Download nRF Connect SDK v2.1.0.

Building with nRF Connect VSCode plugin

• In Visual Studio Code go to marketplace and search for "nrf connect".
• Install the nRF Connect Extension Pack (this will install all required extensions at once).
• Click on the nRF Connect extension and select "Add an existing application"
• Choose the folder c209-aoa-tag (or the folder name you choose when cloning this repository).
• Press CTRL+SHIFT+P and search/select "nRF Connect: Select nRF Connect SDK"
• Press "Yes" in the popup asking if you want to change it.
• In the dropdown you should see the path where nRF Connect was installed before. Choose it.
• Under "applications" press "No build configurations Click to create one".
• Choose all boards and select ubx_evkninab4_nrf52833 in the drowdown.
• Press "Build Configuration" button.
• Now project should build successfully.

Building with command line

• Open nRF Connect for Desktops Toolchain Manager.
• Right next to the "nRF Connect SDK v2.1.0" you have a dropdown, click "Open bash". This step is not required, but it will set up the necessary environment variables for you.
• cd to project folder
• west build -b ubx_evkninab4_nrf52833
• west flash
• west flash only will be enough for building + flashing after that, specifying the board is only needed on the first build.

Release vs. Debug build

The prj.conf is split into multiple files, first there is prj_base.conf and that contains all common config for both release and debug. Then there are prj_debug.conf and prj_release.conf, these contain configurations specific to debug or release, for example compiler optimization level and logging config. By default a debug build is made, to build release run west build -p -b ubx_evkninab4_nrf52833 -- -DRELEASE=1. Those options can also be input when adding the application in the nRF Connect VS Code plugin under "Extra CMake arguments".

Running on other boards

This sample application primarily supports the u-blox C209 application board bundled together with the u-blox C211 or ANT-B10 in the XPLR-AOA kits.

However getting it up and running on other boards which either use NINA-B4 module (like NINA-B4-EVK) or a NRF52833 DK is only a matter of selecting the appropriate board file.

Building the application to use with OpenCPU DFU Bootloader

C209 boards come pre flashed with a DFU bootloader. To build a binary that is compatible with that add -DNRF_DFU_BOOT_SUPPORT=1 to build arguments. If the pre-flashed bootloader has been erased or overwritten then flash the dfu_bootloader/mbr_nrf52_2.4.1_mbr.hex and dfu_bootloader/nrf52833_xxaa_bootloader.hex using using J-Flash Lite/nrfjprog or similar tool to restore it. See the following complete steps to build and flash.

• Add -DNRF_DFU_BOOT_SUPPORT=1 to the build arguments.
• Re-Run CMAKE and re-build
• Copy the zephyr.bin file from build/zephyr folder to dfu_bootloader.
• In dfu_bootloader run nrfutil pkg generate --hw-version 52 --sd-req 0x00 --application-version 0 --application zephyr.bin app.zip
• To enter DFU mode when an application is flashed hold down SWITCH_2 and click reset.
• In dfu_bootloader run nrfutil dfu serial -pkg app.zip -p COMXXX -b 115200 -fc 1 -t 1
• Now the module will be flashed. It's also possible to keep the "Flash Base Address" to 0x1000 and develop as usual and flashing with SeS or west as it will flash the application on the correct address and it will be started by the open bootloader.

nrfutil executable for flashing with OpenCPU DFU Bootloader can be downloaded from here: https://github.com/NordicSemiconductor/pc-nrfutil/releases

Communication using AT commands

In src/at_host there is a very basic AT command handler.

Over UART

When the application boots it will accept AT commands over the UART for 10s before it shuts off the UART in order to save power. If a successful AT command was sent within 10 seconds the application will keep UART enabled until it's reset.

Over BLE (Nordic UART Service)

If Kconfig CONFIG_ALLOW_REMOTE_AT_OVER_NUS is enabled (default yes) then the application will accept AT commands over the Nordic UART Service. Each write will be parsed as an AT command so no need for line termination characters etc.

Using the Sensors on the C209

The C209 application board comes with some sensors. Study src/sensors.c for example how to get data from the sensors. If CONFIG_SEND_SENSOR_DATA_IN_PER_ADV_DATA is enabled (default n) then sensor data from the BME280 will be sent in the periodic advertising data.

Sending data in periodic advertisements

Data can be sent from the tag to the anchor/scanner using the payload of periodic advertisements, study the usage of btAdvSetPerAdvData when CONFIG_SEND_SENSOR_DATA_IN_PER_ADV_DATA to see how.

Optimizing for power consumption

The factor that affects the power conumption the most is the periodic advertising interval. This can be changed by the switch (sw1) on the board. Other than that the following configuration options also significantly affects the power consumption. To minimize power consumption change in the prj.conf to below values. CONFIG_EXT_ADV_INT_MS_MIN and CONFIG_EXT_ADV_INT_MS_MAX can be set to anything that is acceptable for the use-case. The higher interval, that longer/harder it will be for the scanning anchor to find the tag and initiate the periodic advertising synchronization.

CONFIG_SEND_SENSOR_DATA_IN_PER_ADV_DATA=n
CONFIG_ALLOW_REMOTE_AT_OVER_NUS=n
CONFIG_PERIODIC_LED_BLINK=n

CONFIG_EXT_ADV_INT_MS_MIN=1000
CONFIG_EXT_ADV_INT_MS_MAX=1500

With this setup following power consumption is achieved with the u-blox C209 tag:

Periodic adv. int. (ms)	Power consumption (μA)
50	153
100	92
250	56
1000	38

C209 specific

Due to the design of the C209 HW by default there is a ~300uA current leak coming from the LIS_INT pin. This is due to a external pullup resistor on this pin and the fact that LIS2DW12 by default have an internal pulldown on the same pin. Fortunately LIS2DW12 have a configuration to disable the internal pulldown on INT1 pin and to make the INT1 pin active low instead. The current codebase does not use the LIS_INT/INT1 pin functionality, however if in future it is make sure to configure and check so that the Zephyr driver can handle swapped polarity of INT1/2 pins of the LIS2DW12.

The fix for minimal power consumption can be found in sensors.c file, check the function configureLis2dw12Default.

Code formatting and style

Code formatting and style follows ubxlib.

To automatically format the code run:

./tools/format_code.sh

Using the application

Please review the user guide for more details on how to use the XPLR-AOA-1 and XPLR-AOA-2 kits.

More information about the hardware kits

For more information about the hardware kits as well as ordering information, please visit the XPLR-AOA-1 product page and XPLR-AOA-2 product page.

License

The software in this repository is Apache 2.0 licensed and copyright u-blox:

In all cases copyright, and our thanks, remain with the original authors.