###### tags: `ROSKY2` `ROS2` `Jetson Nano` `reComputer-J1010` `lidar detection`
# CH 3: ROSKY2 - Detect distance with lidar
In this note, user will use lidar to detect distance of specific direction
## Hardware user have to prepare before doing...
1. [ROSKY2](https://www.icshop.com.tw/product-page.php?28598)
2. A host machine with the operating system is Window 10(above) or Ubuntu.
---
## Some things user should know before operating...
Please check the note and documentation below:
- [CH 1. ROSKY2 - remotely log in](https://hackmd.io/@weichih-lin/ROSKY2_log_in_remotely)
- [ros2 service documentation](https://docs.ros.org/en/foxy/Tutorials/Beginner-CLI-Tools/Understanding-ROS2-Services/Understanding-ROS2-Services.html)
Now let’s go ahead to use lidar.
---
## Step 1. Open Terminator in ROSKY2 through remote desktop
### Step 1-1. Open terminal on the remote desktop
Because of the keyboard shortcut keys in NoMachine, user can not use the keyboard keys 【ctrl】+【alt】+【T】to open the terminal quickly.
Please right-click the mouse on the remote desktop to open the menu item and then choose【Open Terminal】to open terminal.
Once user see the roe_menu is shown on the terminal, please choose【2】to start the operating environment for ROSKY2.
### Step 1-2. Open terminator on the remote desktop
Terminator is a nice terminal emulator, please check the [Terminator’s documentation](https://terminator-gtk3.readthedocs.io/en/latest/) to know more detail.
User can type the command command to start terminator:
```bash=
$ terminator
```
Once start the terminator successfully, user can see ros_menu is shown on the terminator. Like the operation in [step 1-1](#Step-1-1-Open-terminal-on-the-remote-desktop), user have to choose [2] to start the environment for ROSKY2.
More keyboard shortcut in the terminator user can find on the [Terminator’s documentation - Using the keyboard](https://terminator-gtk3.readthedocs.io/en/latest/gettingstarted.html#using-the-keyboard).
## Step 2. Start the communication with all sensors, motor control board and more on ROSKY2
Now user just running the system on the SBC and it can not send/receive data from sensor and more. Hence, user have to start the communication with these to send/receive data.
> **Note**
> Seneors on ROSKY2 will start running after typing the command below. Please make sure **no more things** result in stopping these sensor work, such as **something is on the LiDAR**, **transfer cable connect between host machine and ROSKY2** and more.
Please type the command below in the terminator to start the communication:
```bash=
$ ros2 launch rosky2_bringup bringup.launch.py
```
## Step 3. Run node "detect_distance"
Awesome! User start the communication between ROSKY2 and sensors. Now user can see lidar is rotating now.
From [Step 1-2 in this note](#Step-1-2-Open-terminator-on-the-remote-desktop), user can know that use the keyboard shortcut 【ctrl】+【shift】+【E】 in terminator to split terminal vertically. The same thing is choosing 【2】 to start the environment for ROSKY2 after user opening ros_menu successfully.
Now is ready to detect the distance from specific direction, please type the command below in terminal to start the node "detect_distance":
```bash=
$ ros2 run wall_follower detect_distance --ros-args -r /detect_distance/scan:=/scan
```
After running successfully, user can see the distance form the direction "BACK":
Please feel free to put something behind ROSKY2 and then check what the information happen on the terminal.
## Step 4. Change direction to detect distance
If user want to chang the direction to detect distance, please use the keyboard shortcut 【ctrl】+【shift】+【O】in terminator to split terminal horizontally and choose【2】to start the environment for ROSKY2 after user opening ros_menu successfully.
Next, please type the command below to call the ROS2 service "/detect_distance/update_direction" for changing the direction detect:
```bash=
$ ros2 service call /detect_distance/update_direction rosky2_interfaces/srv/DirectionUpdate "{data: [direction]}"
```
> **Note**
> **User have to type the direction to replace [direction]. Until now, just these direction can use: back, right, front, left.**
Below the image is the example that change the direction from back to front:
And user can find infromation change from "BACK" to "FRONT" in the window that the node "detect_distance" running.
## Step 5. Shutdown all running node.
If user finished the keyboard teleop for ROSKY2, please remember to shutdown all running node through the shortcut key 【ctrl】+【C】 in terminal.
## Next
User can continue the note -> [CH4: wall_fallower](https://hackmd.io/@weichih-lin/ROSKY2_wall_follower)
Please have fun to use ROSKY2 :)
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