Add GPIO section in README

README.md

@@ -76,16 +76,17 @@ This project was developed for ROS 2 Foxy (Ubuntu 20.04) and Humble (Ubuntu 22.0
    source install/setup.bash
    ```
 
-**NOTE**: Remember to source the setup file and the workspace whenever a new terminal is opened:
-
-```bash
-source /opt/ros/humble/setup.bash
-source ~/flexiv_ros2_ws/install/setup.bash
-```
+> [!NOTE]
+> Remember to source the setup file and the workspace whenever a new terminal is opened:
+> ```bash
+> source /opt/ros/humble/setup.bash
+> source ~/flexiv_ros2_ws/install/setup.bash
+> ```
 
 ## Usage
 
-**NOTE**: the instruction below is only a quick reference, see the [Flexiv ROS 2 Documentation](https://rdk.flexiv.com/manual/ros2_packages.html) for more information.
+> [!NOTE]
+> The instruction below is only a quick reference, see the [Flexiv ROS 2 Documentation](https://rdk.flexiv.com/manual/ros2_packages.html) for more information.
 
 The prerequisites of using ROS 2 with Flexiv Rizon robot are [enable RDK on the robot server](https://rdk.flexiv.com/manual/getting_started.html#activate-rdk-server) and [establish connection](https://rdk.flexiv.com/manual/getting_started.html#establish-connection) between the workstation PC and the robot.
 
@@ -111,13 +112,15 @@ The main launch file to start the robot driver is the `rizon.launch.py` - it loa
      ros2 launch flexiv_bringup rizon.launch.py robot_ip:=[robot_ip] local_ip:=[local_ip] rizon_type:=rizon4
      ```
 
-     **NOTE**: To test whether the connection between ROS and the robot is established, you could disable the starting of RViz first by setting the `start_rviz` launch argument to false.
    - Test with fake hardware (`ros2_control` capability):
 
      ```bash
      ros2 launch flexiv_bringup rizon.launch.py robot_ip:=dont-care local_ip:=dont-care use_fake_hardware:=true
      ```
 
+> [!TIP]
+> To test whether the connection between ROS and the robot is established, you could disable the starting of RViz first by setting the `start_rviz` launch argument to false.
+
 2. Publish commands to controllers
 
    - To send the goal position to the controller by using the node from `flexiv_test_nodes`, start the following command in a new terminal:
@@ -133,8 +136,6 @@ The main launch file to start the robot driver is the `rizon.launch.py` - it loa
      ros2 launch flexiv_bringup rizon.launch.py robot_ip:=[robot_ip] local_ip:=[local_ip] robot_controller:=joint_impedance_controller
      ```
 
-     **NOTE**: The command starts the robot in the joint torque mode. In this mode, gravity and friction are compensated **only** for the robot **without** any attached objects (e.g. the gripper, camera).
-
      Open a new terminal and run the launch file:
 
      ```bash
@@ -143,7 +144,11 @@ The main launch file to start the robot driver is the `rizon.launch.py` - it loa
 
      The robot should run a sine-sweep motion with joint impedance control.
 
-     **NOTE**: joint impedance control is not supported in fake/simulated hardware.
+> [!NOTE]
+> The command starts the robot in the joint torque mode. In this mode, gravity and friction are compensated **only** for the robot **without** any attached objects (e.g. the gripper, camera).
+
+> [!NOTE]
+> Joint impedance control is not supported in fake/simulated hardware.
 
 ### Using MoveIt
 
@@ -169,4 +174,15 @@ The robot driver (`rizon.launch.py`) publishes the following feedback states to
 - `/force_torque_sensor_broadcaster/wrench`: Force-torque (FT) sensor raw reading in flange frame: $^{flange}F_{raw}$ in force $[N]$ and moment $[Nm]$. The value is 0 if no FT sensor is installed. [[`geometry_msgs/WrenchStamped.msg`](https://docs.ros.org/en/noetic/api/geometry_msgs/html/msg/WrenchStamped.html)]
 - `/tcp_pose_broadcaster/tcp_pose`: Measured TCP pose expressed in base frame $^{0}T_{TCP}$ in position $[m]$ and quaternion. [[`geometry_msgs/PoseStamped.msg`](https://docs.ros.org/en/noetic/api/geometry_msgs/html/msg/PoseStamped.html)]
 
-**NOTE**: The topic names of the broadcasters are specified in `flexiv_bringup/config/rizon_controllers.yaml`
+> [!NOTE]
+> The topic names of the broadcasters are specified in `flexiv_bringup/config/rizon_controllers.yaml`
+
+### GPIO
+
+All digital inputs on the robot control box can be accessed via the ROS topic `/gpio_controller/gpio_inputs`, which publishes the current state of all the 16 digital input ports *(True: port high, false: port low)*.
+
+The digital output ports on the control box can be set by publishing to the topic `/gpio_controller/gpio_outputs`. For example:
+
+```bash
+ros2 topic pub /gpio_controller/gpio_outputs flexiv_msgs/msg/GPIOStates "{states: [{pin: 0, state: true}, {pin: 2, state: true}]}"
+```