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ROS driver for the u-blox ZED-F9P GNSS receiver

Brief setup instructions by Jonas Beuchert, original readme below.

You need a C++11 compiler, ROS, Eigen 3.3.3, and Boost, but they might be installed already.

Install Google's glog library for message output:

sudo apt-get install libgoogle-glog-dev

Clone gnss_comm for ROS message definitions:

cd spot_git
git clone [email protected]:HKUST-Aerial-Robotics/gnss_comm.git

Clone this repository:

git clone [email protected]:ori-drs/ublox_driver.git

Depending on you desired configuration, you might need to change the configuration file, but it should work out-of-the-box. Sometimes, you need to change the port. Usually, it is dev/ttyACM0 (default) or /dev/ttyACM1.

Create symbolic links from you catkin workspace to the cloned repositories

cd ../spot_ws/src
ln -s ~/spot_git/gnss_comm/ .
ln -s ~/spot_git/ublox_driver/ .

Build the driver using catkin tools:

cd ..
catkin build ublox_driver

Launch roscore in another terminal.

Grant permission to the port, e.g:

sudo chmod 666 /dev/ttyACM0

(Alternatively, add the user permanently to the dialout group with sudo adduser user_name dialout and logout and login again.)

Launch the driver:

source devel/setup.bash
roslaunch ublox_driver ublox_driver.launch

It might be worth it to check out Section 5. below to synchronize the local system time with a global time reference (and, therefore, with the timestamps of the GNSS observations.)

Troubleshooting

If the driver prints the error ubx rxmrawx week=0 error or the error open: No such file or directory, a cause can be that the port in the configuration file is incorrectly set.

If a permission-denied error occurs, then the driver might not have access rights to the port.

If no messages appear despite there being view of the sky, you might have to manually enable the binary messages of the receiver, see below.

Receiver configuration

You can use different software to change the configuration of the receiver firmware (e.g., the measurement frequency or which messages are broadcasted):

  • u-center provides a graphical user interface for Windows. As of writing, v22.07 is the most recent version that supports the ZED-F9P chip.
  • ubxtool is a Linux/MacOS command line tool that is part of GPSd. To get the full functionality for the ZED-F9P, you need a recent version. I built GPSd v25.0 from source following these instructions and it worked. Basically, I had to do the following:
sudo apt install scons
wget http://download.savannah.gnu.org/releases/gpsd/gpsd-3.25.tar.gz
tar -xzf gpsd-3.25.tar.gz
cd gpsd-3.25/
scons
sudo scons udev-install
export PYTHONPATH=${PYTHONPATH}:/usr/local/lib/python3/dist-packages
  • Of course, you can also just figure out the binary representation of your configuration commands in the u-blox F9 interface description and just write them straight to your serial port /dev/ttyACM0...

Enabeling and disabling messages

The receiver can broadcast two types of messages: human-readable NMEA messages and binary UBX messages. This driver needs the binary messages. If only NMEA meesages are enabled, you need to manually enable the binary messages (and, optionally, turn off NMEA messages). Specifically, you need to enable one or more of the following messages (depending on your use case):

  • UBX-RXM-RAWX for raw GNSS measurements from individual satellites.
  • UBX-RXM-SFRBX for satellite navigation data broadcasted by the satellites.
  • UBX-NAV-PVT for pre-computed GNSS fixes.

You can find a description of all messages in the u-blox F9 interface description . To enable one or more of these, install u-center or GPSd/ubxtool, as described above. If you use u-center, start the graphical user interface, connect the receiver via the left-most button, open the Messages View and enable/disable messages by right-clicking on them. Next, head to the Configuration View, select CFG, then Save current configuration, then Send to save these settings to the flash on-board the F9P module. If you use ubxtool, then you can use some or all of the following commands:

  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0x01,0x07,1 to enable UBX-NAV-PVT.
  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0x01,0x07,0 to disable UBX-NAV-PVT.
  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0x02,0x13,1 to enable UBX-RXM-SFRBX.
  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0x02,0x13,0 to disable UBX-RXM-SFRBX.
  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0x02,0x15,1 to enable UBX-RXM-RAWX.
  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0x02,0x15,0 to disable UBX-RXM-RAWX.
  • for i in 0x0a 0x45 0x44 0x09 0x00 0x01 0x43 0x42 0x0d 0x40 0x47 0x06 0x02 0x07 0x03 0x0b 0x04 0x41 0x0f 0x05 0x08; do ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf0,$i,1; done to enable all standard NMEA messages.
  • for i in 0x0a 0x45 0x44 0x09 0x00 0x01 0x43 0x42 0x0d 0x40 0x47 0x06 0x02 0x07 0x03 0x0b 0x04 0x41 0x0f 0x05 0x08; do ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf0,$i,0; done to disable all standard NMEA messages.
  • for i in 0x00 0x01 0x0d 0x02 0x04 0x05 0x08; do ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf7,$i,1; done to enable all secondary NMEA messages.
  • for i in 0x00 0x01 0x0d 0x02 0x04 0x05 0x08; do ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf7,$i,0; done to disable all secondary NMEA messages.
  • for i in 0x41 0x00 0x40 0x03 0x04; do ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf1,$i,1; done to enable all u-blox NMEA messages.
  • for i in 0x41 0x00 0x40 0x03 0x04; do ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf1,$i,0; done to disable all u-blox NMEA messages.
  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf0,0x00,1 to enable only the NMEA fix output (GGA).
  • ubxtool -f /dev/ttyACM0 -p CFG-MSG,0xf0,0x00,0 to disable only the NMEA fix output (GGA).
  • ubxtool -f /dev/ttyACM0 -p CFG-RATE,100 to set the measurement interval to 100 ms (= the measurement rate to 10 Hz). The default is 100 ms, but you might want to choose something else.

Afterwards, run ubxtool -f /dev/ttyACM0 -p SAVE.

Differential GNSS (D-GNSS)

If you want to obtain differential fixes in real-time (with potentially cm-accuracy), then you need to feed data from a nearby base station to the GNSS receiver.

If the receiver has Bluetooth (like the C099-F9P), then you can do the following:

  • Pair the receiver with your phone via Bluetooth. The C099-F9P should have a name of the form BT_C099-F9P_XXXX. The receiver does not appear as a Bluetooth device? For the C099-F9P, you might have to enable it first: Plug in the receiver via USB, open a serial terminal (baud rate: 460800; serial frame: 8 bits, 1 stop bit, no parity; flow control: none; local echo off/disabled) and run the command /bt_visible/run.
  • Install an NTRIP client (for example, Lefebure, YCServer, or Bluecover) on your phone.
  • In the receiver settings, select the Bluetooth option and connect to the GNSS receiver.
  • In the NTRIP caster section, select a base station. For example, the one near Bicester has the IP address 3.23.52.207 (rtk2go.com), the port 2101, the mount point / stream name OXTS1, and no username and no password. It uses the NTRIP Rev 1 protocol. You can find other base stations in this table. For example, you could search for stations with country code GBR, which provide at least GPS, Glonass (GLO), Galileo (GAL), and BeiDou (BDS) data. However, some streams might be password protected. Another option is to use one of the NTRIP broadcatsers from the BKG. Their streams are listed here and the host URL is igs-ip.net. For example, the station LICC00GBR is in London. However, you need to register first, which is free. Then, enter your username and password in your NTRIP client.
  • Run the client and stream the data from the base to the receiver.
  • Check that the flag diff_soln in the fixes in the receiver_pvt topic is True after your started to stream the data.

If the receiver does not have Bluetooth, but it is connected to a NUC and the NUC has internet, then follow the instructions in the section Obtain RTK Solution (Optional) below.

Summary of steps here.

Install RTKLIB's NTRIP client:

git clone https://github.com/tomojitakasu/RTKLIB.git
cd RTKLIB/
git checkout rtklib_2.4.3
cd app/consapp/str2str/gcc/
make

Connect to the NTRIP stream of the base station:

./str2str -in ntrip://${NTRIP_SITE}:${NTRIP_PORT}/${MOUNT_POINT} -out tcpsvr://:3503

For example, for the stream from the base close to Bicester:

./str2str -in ntrip://3.23.52.207:2101/OXTS1 -out tcpsvr://:3503

Set the input_rtcm option to 1 in config/driver_config.yaml.

Launch the ROS node as usual:

roslaunch ublox_driver ublox_driver.launch

Again, check that the flag diff_soln in the fixes in the receiver_pvt topic is True.

To obtain differential fixes offline with post-processing, you can do the following:

  • Log the stream from a base station during your trial with an NTRIP client of your choice.
  • Convert the log into the RINEX format, if necessary.
  • Convert the GNSS observations in your rosbag into RINEX format using this tool.
  • Install RTKLIB or this well-maintained fork.
  • Get the satellite navigation data from here. Choose the correct year and day-of-the year and the file named BRDM00DLR_S_YYYYDDD0000_01D_MN.rnx.gz. (Alternatively, get the satellite navigation data from the base station, too.)
  • Optionally, get SP3, CLK, ERP, and ION files from here. Choose the correct GPS week number and the correct day of the week (Sunday=0, Monday=1, ...) to identify the correct directory and file. Files starting with igs are better than files starting igr, which are better than the igu files. Using these files should improve performance since they are more accurate than the broadcasted data mentioned above.
  • Use RTKLIB's RTKPOST program with all these files to obatain a differential solution. If you are uncertain which options to choose, then have a look at the section in the RTKLIB manual that describes RTKPOST. Probably the Kinematic mode is a good starting point.

Assisted GNSS (A-GNSS)

You do not want to use differential GNSS, but want to reduce your time-to-first-fix to a few seconds? Then this section is for you. All you need is an internet connection at time of configuration.

The basic idea is to supply the receiver with assistance data, like satellite navigation data or an initial position during start-up. The first step is to download up-to-date satellite navigation data from the internet. The second step is to flash it to the receiver.

There are several options where to source the satellite navigation data. One option is u-blox' AssistNow Service. Data from AssistNow Online is valid for a few hours, data from AssistNow Offline up to 5 weeks. To use the services, you need a token. If based in the ORI, you can try to use my token. Otherwise, you can register for one. Then just connect your receiver via USB and do the following to download data from AssistNow Online and send it to the receiver's serial port:

token="your_token"
latitude="51.751920"
longitude="-1.258180"
accuracy="3000"
curl "https://online-live1.services.u-blox.com/GetOnlineData.ashx?token=$token;gnss=gps,glo,gal,bds,qzss;datatype=eph,alm,aux,pos;lat=$latitude;lon=$longitude;pacc=$accuracy" -o /dev/ttyACM0

The latitude, longitude, and accuracy parameters are optional. In this example, I use the Carfax Tower as the initial location (specified in decimal degrees) and an uncertainity of this initial location of 3000 meter. For more parameters, check out the user guide.

The download size should be several kilobytes. If it's just a few bytes, then the request did not work. You can check the receiver's internal database with ubxtool -f /dev/ttyACM0 -c 0x01,0x34. There should be lots of satellites after transferring the assistance data. If you wish to reset the database for any reason, run ubxtool -f /dev/ttyACM0 -p COLDBOOT.

You can download data from AssistNow Offline with

curl "https://offline-live1.services.u-blox.com/GetOfflineData.ashx?token=$token;gnss=gps,glo,bds,gal"

However, I have not been able to succesfully use the data on a receiver yet.

Another option to load assistance data to your receiver is to briefly connect it to your phone (via USB or Bluetooth using, e.g., YCServer, Bluecover, or Lefebure) and to tap into an online NTRIP server stream, as described in the D-GNSS section above.

ublox_driver

Authors/Maintainers: CAO Shaozu (shaozu.cao AT gmail.com)

The ublox_driver provides essential functionalities for u-blox GNSS receivers. This package is originally designed for u-blox ZED-F9P module according to the specification UBX-18010854, but should also be compatible to other 8-series or 9-series u-blox receivers as long as the interface is the same.

The following diagram shows all possible input and output options supported by ublox_driver.

ublox_driver diagram!

1. Prerequisites

1.1 C++11 Compiler

This package requires some features of C++11.

1.2 ROS

This package is developed under ROS Kinetic environment.

1.3 Eigen

We use Eigen 3.3.3 for matrix manipulation.

1.4 Boost

Our software utilizes Boost library for serial and socket manipulation. Using command sudo apt-get install libboost-all-dev to install Boost.

1.5 gnss_comm

This package also requires gnss_comm for ROS message definitions and some utility functions. Follow those instructions to build the gnss_comm package.

2. Build ublox_driver

Clone the repository to your catkin workspace (for example ~/catkin_ws/):

cd ~/catkin_ws/src/
git clone https://github.com/HKUST-Aerial-Robotics/ublox_driver.git

Then build the package with:

cd ~/catkin_ws/
catkin_make
source ~/catkin_ws/devel/setup.bash

3. Run with your u-blox receiver

Our software can take the serial stream from the u-blox receiver as an input source. Before running the package, you need to configure your receiver using u-center to output at least UBX-RXM-RAWX, UBX-RXM-SFRBX and UBX-NAV-PVT messages to a specific serial port (a sample config used in our system can be found at config/ucenter_config_f9p_gvins.txt). Then connecting your computer(Linux) with the receiver, make sure the serial port appears as a file in the /dev/ directory. Then add your account to dialout group to obtain permission on serial r/w operation via (no need to substitute $USER):

sudo usermod -aG dialout $USER

Open config/driver_config.yaml, set online and to_ros to 1, and adjust input_serial_port and serial_baud_rate according to your setting. Run the package with:

roslaunch ublox_driver ublox_driver.launch

Open another terminal, echo the ROS message by:

rostopic echo /ublox_driver/receiver_lla

If everything goes smoothly, there should be some ROS messages coming out. Note that some ROS topics remain inactive until the receiver gets GNSS signals.

Besides the ROS message, you can record the serial stream to a file(to_file option) or forward the stream to another serial port(to_serial option). All output options can be turned on simultaneously.

Obtain RTK Solution (Optional)

If your receiver owns an internal RTK engine (for example, ZED-F9P), you can input RTCM messages from the GNSS base station to the receiver in order to obtain the cm-level accurate RTK localization result. Our software can forward the RTCM stream from a local socket to the receiver's serial port. Nowadays many GNSS stations distribute their RTCM streams via NTRIP protocol and you can easily fetch the NTRIP data and map it to a local socket via RTKLIB. Following those commands to build RTKLIB and setup the RTCM stream:

git clone https://github.com/tomojitakasu/RTKLIB.git
cd RTKLIB/
git checkout rtklib_2.4.3
cd app/consapp/str2str/gcc/
make
./str2str -in ntrip://${NTRIP_SITE}:${NTRIP_PORT}/${MOUNT_POINT} -out tcpsvr://:3503

Then set the input_rtcm option to 1 in config/driver_config.yaml and launch the ros node with:

roslaunch ublox_driver ublox_driver.launch

If the field carr_soln in /ublox_driver/receiver_pvt message becomes 2, the RTK is in fix status. If you find the location of the GNSS base station reported in the RTCM message is somehow biased, you can apply correction via the variable rtk_correction_ecef in the config file.

4. Playback Log Files

Our package can also take an log file as the input. The log file can be recorded via u-center, RTKLIB or our package itself. To playback the log file, you need to set online to 0 and point ubx_filepath to your log file in the config file. Then launch the ros node with:

roslaunch ublox_driver ublox_driver.launch

Similar to the online receiver manner, all three output options are also supported in the playback mode. Note that the playback speed is controlled by the serial_baud_rate variable in the config file.

5. Synchronize System Time

In addition to message parsing and delivery, ublox_driver can also synchronize the local system time to the global time without the need of internet connection. Note that such synchronization is only in a coarse level and the accuracy is not guaranteed. To perform such synchronization, you need to set UTC_OFFSET macro in src/sync_system_time.cpp according to your timezone. Recompile and launch the driver with:

roslaunch ublox_driver ublox_driver.launch

Then open another terminal and run commands:

sudo su
source /opt/ros/kinetic/setup.bash
source ${YOUR_CATKIN_WORKSPACE}/devel/setup.bash
rosrun ublox_driver sync_system_time

The system time will be synchronized to the global time when the receiver gets a valid PVT solution.

6. Todo List

  • Config u-blox receiver when the driver gets launched
  • Infer timezone from geodetic location when sync time
  • Optimize time-sync function to improve precision

7. Acknowledgements

Many of the ephemeris parsing functions in our package are adapted from RTKLIB. We use mini-yaml for config parsing.

8. License

The source code is released under GPLv3 license.