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Add project code
Signed-off-by: Soren Friis <[email protected]>
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‎.gitignore‎

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build
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.idea
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cmake-build*

‎CMakeLists.txt‎

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# Copyright (C) 2021, Soren Friis
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#
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# SPDX-License-Identifier: Apache-2.0
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#
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# Open Drone ID Linux transmitter example.
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#
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# Maintainer: Soren Friis
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# [email protected]
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cmake_minimum_required (VERSION 3.10)
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project (opendroneid-transmit)
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SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DCONFIG_CTRL_IFACE -DCONFIG_CTRL_IFACE_UNIX")
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if(DEFINED ODID_AUTH_MAX_PAGES)
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message(STATUS "Using externally defined ODID_AUTH_MAX_PAGES value")
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set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DODID_AUTH_MAX_PAGES=${ODID_AUTH_MAX_PAGES}")
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endif()
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if(DEFINED ODID_BASIC_ID_MAX_MESSAGES)
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message(STATUS "Using externally defined ODID_BASIC_ID_MAX_MESSAGES value")
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set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DODID_BASIC_ID_MAX_MESSAGES=${ODID_BASIC_ID_MAX_MESSAGES}")
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endif()
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include_directories(
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hostapd/src
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hostapd/src/utils
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core-c/libopendroneid
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bluez
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)
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add_executable(transmit
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hostapd/src/utils/os_unix.c
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hostapd/src/common/cli.c
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hostapd/src/common/wpa_ctrl.c
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hostapd/src/utils/common.c
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hostapd/src/utils/edit.c
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hostapd/src/utils/eloop.c
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hostapd/src/utils/wpa_debug.c
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core-c/libopendroneid/opendroneid.c
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bluez/lib/hci.c
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bluez/lib/bluetooth.c
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ap_interface.c
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utils.c
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bluetooth.c
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wifi_beacon.c
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transmit.c
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print_bt_features.c
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)
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target_link_libraries(transmit
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pthread
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m
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)

‎README.md‎

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# transmitter-linux
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# Open Drone ID transmitter example for Linux
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This program supports transmitting static drone ID data via Wi-Fi Beacon or Bluetooth on a desktop Linux PC.
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For further information about Open Drone ID and the related specifications, please see the documentation in [opendroneid-core-c](https://github.com/opendroneid/opendroneid-core-c).
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The drone ID data is just static data, since the main purpose is to demonstrate how to setup the Bluetooth and Wi-Fi Beacon HW + SW to transmit valid drone ID data.
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This could easily be extended to simulate a bit more dynamic flight example.
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## How to compile
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The below instructions have been tested on Ubuntu 20.04 and on Raspbian 10 (Buster).
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```
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git clone [email protected]:opendroneid/transmitter-linux.git
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cd transmitter-linux
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git submodule update --init
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```
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The Bluez source code repository has been set to version 5.53, since this matched the version installed on Ubuntu 20.04.
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It might be required to check what version of Bluez is installed on your environment and adjust accordingly:
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Check any of `btmon --version`, `btmgmt --version`, `bluetoothctl --version`, `hcitool` or `hciconfig`.
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Compile hostapd:
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```
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sudo apt install build-essential git libpcap-dev libsqlite3-dev binutils-dev bc pkg-config libssl-dev libiberty-dev libdbus-1-dev libnl-3-dev libnl-genl-3-dev libnl-route-3-dev
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cd hostapd/hostapd
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cp defconfig .config
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make -j4
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cd -
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```
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Compile the transmitter example application:
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```
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mkdir build && cd build
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cmake ../.
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make -j4
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```
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## Command line parameters
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* `b` Enable Wi-Fi Beacon transmission
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* `l` Enable Bluetooth 4 Legacy Advertising transmission using non-Extended Advertising API
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* `4` Enable Bluetooth 4 Legacy Advertising transmission using Extended Advertising API
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* `5` Enable Bluetooth 5 Long Range + Extended Advertising transmission
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* `p` Use message packs instead of single messages
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## Starting Wi-Fi Beacon transmission
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The Wi-Fi Beacon transmission only works properly when the PC is not connected to any Wi-Fi hotspots.
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If it is connected, it somehow prevents configuring the Wi-Fi HW to act as a local access point.
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On Ubuntu, open the system settings -> Wi-Fi and for each of the networks that are stored on the machine, click the gear icon and then click forget network.
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On the Raspberry Pi OS, try first to click the Wi-Fi icon in the top right corner.
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For each network that is already configured, right-click it and forget the network.
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It is also possible that there are connection settings stored in the file `/etc/wpa_supplicant/wpa_supplicant.conf`.
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Edit the file and delete/comment out all known Wi-Fi networks, then reboot.
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NOTE: When tested, the beacon transmit only partly worked on Raspberry Pi 3 and 4.
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The pre-defined single location message that can be uncommented in the beacon.conf file works okay.
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However, any data that the `transmit` program tries to write to the host ap daemon does not appear to be used.
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It is not clear why this is so.
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Check that there is nothing preventing the usage of the Wi-Fi HW by running the tool `rfkill`.
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Any SW block should be possible to unblock via the same tool.
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To start hostapd, a configuration file must be present with the following content.
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E.g. modify the beacon.conf that is provided in the root of the project folder.
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Make sure the second line matches the name of your WLAN device.
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Can be checked e.g. with `ip link show` or `iw dev`:
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```
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country_code=DE
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interface=wlan0
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ssid=DroneIDTest
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hw_mode=g
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channel=6
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macaddr_acl=0
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auth_algs=1
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ignore_broadcast_ssid=0
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wpa=2
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wpa_passphrase=thisisaverylongpassword
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wpa_key_mgmt=WPA-PSK
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wpa_pairwise=TKIP
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rsn_pairwise=CCMP
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ctrl_interface=/var/run/hostapd
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beacon_int=200 # Does this work? Doesn't seem to have any effect?
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#This is an empty information element. dd indicates hex. 01 is the length of the data and 00 the actual data:
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vendor_elements=dd0100
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#This information element has one fixed Location message:
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#vendor_elements=dd1EFA0BBC0D00102038000058D6DF1D9055A308820DC10ACF072803D20F0100
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```
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Open a separate shell at the top of the project and start the hostapd daemon.
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This only works with `sudo` rights:
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```
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sudo hostapd/hostapd/hostapd beacon.conf
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```
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In the original shell, start the opendroneid transmitter.
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Again, this only works with `sudo` rights:
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```
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sudo ./transmit b p
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```
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This has been tested on a [CometLake Z490 desktop](https://rog.asus.com/motherboards/rog-strix/rog-strix-z490-i-gaming-model) with built-in Wi-Fi HW on the motherboard.
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For some reason, a fair amount of the messages being sent to hostapd are not received or at least not properly acknowledged by the lower SW layers.
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This is clearly visible when following the command line output.
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It is not clear why this is happening.
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Another unclear issue is that setting the beacon interval in the beacon.conf file does not seem to have any effect.
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## Starting Bluetooth transmission
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The program must be run with `sudo` rights:
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```
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sudo ./transmit 5 p
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```
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For educational purposes, it is possible to follow the HCI command flow using the tool `sudo btmon`.
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This requires Bluez to be installed: `sudo apt install bluez`.
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This has been tested on a [CometLake Z490 desktop](https://rog.asus.com/motherboards/rog-strix/rog-strix-z490-i-gaming-model) with built-in Bluetooth HW on the motherboard.
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On this HW, BT4 Legacy Advertisements using the Extended Advertising API (`option 4`) and BT5 Long Range + Extended Advertisements (`option 5 p`) would work just fine when run individually.
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However, when configuring both simultaneously, for some reason the HW/driver SW would only broadcast the BT4 signals.
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Using the BT4 Legacy Advertising non-Extended Advertising HCI commands (`option l`) for some reason didn't work.
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When tested on a Raspberry Pi 3 and 4, the Extended Advertising HCI interface commands are not supported (`option 4` and `option 5 p`).
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Probably due to the HW/driver only supporting BT4 Legacy Advertising.
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The older BT4 Legacy non-Extended Advertising HCI commands (`option l`) worked okay.
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## How to clean up
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If the program is terminated abnormally, Beacon and Bluetooth broadcasts can remain running.
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* To stop Beacon broadcast, stop the `hostapd` instance.
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It can be difficult to stop the `transmit` instance. After stopping `hostapd`, use `sudo pkill transmit`.
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* To stop Bluetooth, use `sudo btmgmt power off` and then `sudo btmgmt power on`.

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