/ros1_zed_f9r_gps

A ROS noetic implementation of a previously ROS2 package.

Primary LanguageCMake

README

This is guide on streaming GPS data from SparkFun GPS-RTK Dead Reckoning pHAT for Raspberry Pi (ZED-F9R) through ROS. Since our project requires ROS1, I installed Ubuntu 20.04 on the raspberry pi.

Install Ubuntu 20.04 on raspberry pi.

There is no official image for ubuntu 20.04 desktop for raspberry pi. However, you can install ubuntu 20.04 server

Enable UART on raspberry pi for Ubuntu

This steps enables serial communication from the GPS module to ubuntu. I followed the guide here, but I listed them below for your convenience.

  1. Disable serial-getty@ttyS0.service
sudo systemctl stop serial-getty@ttyS0.service
sudo systemctl disable serial-getty@ttyS0.service
sudo systemctl mask serial-getty@ttyS0.service
  1. Setup udev rules, create a new file /etc/udev/rules.d/10-local.rules and write the following linse.
KERNEL=="ttyS0", SYMLINK+="serial0" GROUP="tty" MODE="0660"
KERNEL=="ttyAMA0", SYMLINK+="serial1" GROUP="tty" MODE="0660"

Reload udev rules: sudo udevadm control --reload-rules && sudo udevadm trigger

  1. Add user to tty group: sudo adduser ubuntu tty (assuming default ubuntu username ubuntu, feel free to add your own username.)

  2. Delete substring console=serial0,115200 from /boot/firmware/cmdline.txt. There is a single line in this file, just remove the substring from the line.

  3. Restart sudo reboot

Note that I have not tested this on a raspberry pi yet

When booting raspberrypi, do not plug in the pHAT module. Signals from UART will interrupt boot process. Plugin pHAT after the pi is booted.

When plugging in pHAT, tilted the pHAT so that the power pins are connected last. For some reason if the power pins are touched first, raspberrypi will reboot and cause the issue mentioned above.

TODO: disable UART temporarily during boot should solve this problem, will update once I manage to get it working.

Download ublox python package and customize

Download sparkfun ublox package. (Requires Python3 and pip3, spidev.) sudo pip3 install spidev sudo pip3 install sparkfun-ublox-gps

The default package does not provide functions to parse GPS covariance matrix, but we can easily add our own.

In /usr/local/lib/Python3.x/dist-packages/ublox_gps, after function geo_coords() on line 196, add another function that parse the covariance.

def geo_cov(self):
    # Here we change the message type to COV
    self.send_message(sp.NAV_CLS, self.nav_ms.get('COV'))
    parse_tool = core.Parser([sp.NAV_CLS])
    cls_name, msg_name, payload = parse_tool.receive_from(self.hard_port)
    # There is no scaling factor so we can just return the payload
    return payload

Details on ublox messages can be found here.

Download ROS

Follow the guide here to install ROS Noetic.

Download the package and build.

cd [your_ros_ws]/src
git clone https://github.com/mkoujiri/ros1_zed_f9r_gps.git
cd ..
catkin_make
source devel/setup.bash

To start publishing data, rosrun zed_f9r_gps publish_gps_data.py.