.. _tutorial_ros_driver:

Access the Autopilot with ROS Drivers
=======================================

We provide two ROS packages to interface with the Pursuit autopilot as mentioned in the API section. They are intended for different use cases. The `pursuit_driver <https://gitee.com/cloudkernel-tech/pursuit_driver>`_
is mainly for end-users with no programming basis, while the `mavros <https://gitee.com/cloudkernel-tech/mavros>`_ package is devised for advanced developers to support extensible capabilities in the future such as IOT communication and robot
simulation.

Method 1: pursuit_driver package
----------------------------------

The interface with the pursuit_driver package is enabled by setting parameters in the QGroundcontrol software as:

::

        ROS_LINK_BAUD=115200   #baud rate
        ROS_LINK_EN=1          #enable the pursuit_driver interface

.. image:: ../img/ros_driver/params_pursuit_driver.png
   :height: 350 px
   :width: 750 px
   :scale: 100 %
   :align: center

To start the pursuit_driver in ROS, users have to first locate the USB port for the autopilot with the command. In the official docker container we provide, the default USB
port is /dev/ttyPursuit.

::

        ls /dev/tty*

.. image:: ../img/ros_driver/dev_port.png
   :height: 220 px
   :width: 750 px
   :scale: 100 %
   :align: center

Then the pursuit_driver node can be brought up by:

::

        cd ~/src/catkinws_nav
        source devel/setup.bash

        # launch with default port /dev/ttyPursuit
        roslaunch pursuit_driver pursuit.launch

        # or with the specified USB port, e.g. /dev/ttyUSB0
        roslaunch pursuit_driver pursuit.launch serial_port:='/dev/ttyUSB0'


.. image:: ../img/ros_driver/pursuit_driver_view.png
   :height: 350 px
   :width: 750 px
   :scale: 100 %
   :align: center

The rqt graph of the pursuit_driver node is shown below:

.. image:: ../img/ros_driver/pursuit_driver_rqt.png
   :height: 350 px
   :width: 750 px
   :scale: 100 %
   :align: center


Method 2: mavros package
-----------------------------

The interface with the mavros package is enabled by setting parameters as:

::

        ROS_LINK_EN=0           # enable the mavros interface

        SER_TEL2_BAUD = 921600  # the default baud rate for mavros interface, which is visible only after setting ROS_LINK_EN=0

.. image:: ../img/ros_driver/params_mavros.png
   :height: 350 px
   :width: 750 px
   :scale: 100 %
   :align: center


Users have to locate the USB port for the autopilot in the same way as the pursuit_driver case, and then start the node with:

::

        cd ~/src/catkinws_nav
        source devel/setup.bash

        roslaunch mavros px4.launch fcu_url:='/dev/ttyPursuit:921600'


.. image:: ../img/ros_driver/mavros_cmd.png
   :height: 350 px
   :width: 750 px
   :scale: 100 %
   :align: center

The partial view of rqt graph for mavros node is:

.. image:: ../img/ros_driver/rqt_mavros.png
   :height: 350 px
   :width: 750 px
   :scale: 100 %
   :align: center