- Breakout boards
This is an old revision of the document!
NOTE The TDoA3 mode is experimental. The protocol and implementation might change but is fairly stable.
To try it out you will have to do the following:
The Crazyflie will automatically detect that the positioning system is using TDoA3 and switch to the correct mode. If you want to force the Crazyflie to use TDoA3 on startup, use the LPS_TDOA3_ENABLE=1 compile option
Anchor positions can be set by the python client but it only supports ids 0-7. If you want to use more anchors there is a tool that can be used in the lps-node-firmware repo.
The tool uses a Crazyflie as a bridge to transmit UWB messages to the anchors. When it is started it transmits positions for all anchors over and over,
cat my_position_file.yaml | python3 tools/lpp/set_positions.py
If an anchor is configured to act as a sniffer, it can be used to listen to the UWB messages in the system. To set an anchor to sniffer mode, connect via USB.
Connect the sniffer via USB and check in /dev which port that it uses. Use this as the first argument
The second argument is the output format, use yaml
python3 tools/sniffer/sniffer_binary.py /dev/tty.usbmodem1421 yaml
Pipe the yaml into the TDoA 3 decoder to see TDoA 3 data unpacked
python3 tools/sniffer/sniffer_binary.py /dev/tty.usbmodem1421 yaml | python3 tools/sniffer/tdoa3_decoder.py
This will show all data that the sniffer receives. To limit the output it is possible to filter which anchors to show. Add one or more ids at the end to only show data from only these anchors.
python3 tools/sniffer/sniffer_binary.py /dev/tty.usbmodem1421 yaml | python3 tools/sniffer/tdoa3_decoder.py 2 3
By piping the TDoA 3 data into the TOF tool, the measured anchor to anchor distances will be displayed. By adding the 'm' argument the output will be in meters instead of UWB clock ticks.
python3 tools/sniffer/sniffer_binary.py /dev/tty.usbmodem1421 yaml | python3 tools/sniffer/tdoa3_decoder.py | python3 tools/sniffer/tdoa3_tof.py m
TDoA 3 supports 2D positioning as well. In this mode all anchors can be placed in the same plane. The tag (LPS deck) is expected to move in the XY-plane at a fixed Z.
Recompile the Crazyflie firmware using the LPS_2D_POSITION_HEIGHT compile flag set to the desired Z.
make “EXTRA_CFLAGS=-DLPS_TDOA_USE_V3 -DLPS_TDOA_ENABLE -DLPS_2D_POSITION_HEIGHT=1.2” if the tag will be located at 1.2 meters height.
In this mode the UWB bitrate is lower and the data of messages can be read at a longer distance. The packet rate will be reduced though.
Recompile both Crazyflie and anchors with the LPS_LONGER_RANGE compile flag.
make “EXTRA_CFLAGS=-DLPS_TDOA_USE_V3 -DLPS_TDOA_ENABLE -DLPS_LONGER_RANGE”
It is possible to use a longer preamble, this will also reduce packet rate. There is no compile flag for this setting, it requires some code modifications in the Crazyflie and the anchors. The preamble is used by the anchor radios to detect messages and a longer preamble increase the probability and thus the useful distance. Note that the radios might detect the preamble but fail at reading the data of the packet (see lower bitrate above). The “SFD” LED on the anchor indicates if a preamble has been detected by the radio.