1. Resource introduction

2. Installation System Environment

2.1 Install Raspbian OS on SD Card

STEP1: Download a Raspbian OS

To install Raspbian OS on a SD Card you will need to download a Raspbian OS firstly. User may download the Rasbian OS directly from the official website of raspberry foundation, Ldrobot TOF lidar user manual is based on the version of Raspberry Pi OS (32-bit) with desktop and recommended software as highlighted in the Following chart.
https://www.raspberrypi.org/downloads/raspberry-pi-os/
or https://www.raspberrypi.com/software/operating-systems/
Raspbian os download site of history version：
Raspbian： https://downloads.raspberrypi.org/raspbian/images/
Raspbian full： https://downloads.raspberrypi.org/raspbian_full/images/
Raspbian lite： https://downloads.raspberrypi.org/raspbian_lite/images/

STEP2: Flash Raspbian OS into SD card

After downloading a Raspbian OS, you need to install win32diskimager as the tool to flash Raspbian OS into SD card. After the image file has been flashed into the SD card sucessfully , SD card will automatically display a boot partition.
https://sourceforge.net/projects/win32diskimager/

2.2 Install ROS Melodic On Raspbian OS

Powering up the Raspberry Pi. And then insert the Micro SD card into the Pi SD-cage . Connects the Mini-HDMI cable to your display ,connect mouse and keyboard . Plug in the power cable to turn on the Raspberry Pi. Installation reference tutorial is
http://wiki.ros.org/ROSberryPi/Installing%20ROS%20Melodic%20on%20the%20Raspberry%20Pi

STEP1 Modify the source file of Rasbian OS

• If you are a Chinese user, please modify as follows:

• • $ sudo nano /etc/apt/sources.list Block the existing modification as:

deb http://mirrors.ustc.edu.cn/raspbian/raspbian/ buster main contrib non-free rpi

• • $ sudo nano /etc/apt/sources.list.d/raspi.list Block the existing modification as:

deb https://mirrors.tuna.tsinghua.edu.cn/raspberrypi/ buster main ui

• If you are a user outside of Chinese, please modify as follows:

• • $ sudo nano /etc/apt/sources.list Block the existing modification as:
    Install any source from the following URL: https://www.raspbian.org/RaspbianMirrors
    Example:

[1]
deb http://mirror.nus.edu.sg/raspbian/raspbian/ buster main contrib non-free rpi
[2]
deb http://ftp.jaist.ac.jp/raspbian/ buster main contrib non-free rpi
[3]
deb http://mirror.ox.ac.uk/sites/archive.raspbian.org/archive/raspbian/ buster main contrib nonfree rpi
[4]
deb http://mirrors.ocf.berkeley.edu/raspbian/raspbian/ buster main contrib non-free rpi
[5]
deb http://reflection.oss.ou.edu/raspbian/raspbian/ buster main contrib non-free rpi
[6]
deb http://mirror.liquidtelecom.com/raspbian/raspbian/ buster main contrib non-free rpi
[7]
deb http://mirrordirector.raspbian.org/raspbian/ buster main contrib non-free rpi
[8]
deb https://archive.raspbian.org/raspbian/ buster main contrib non-free rpi
[9]
deb https://mirrors.tuna.tsinghua.edu.cn/raspbian/raspbian/ buster main contrib non-free rpi
[10]
deb http://mirrors.aliyun.com/raspbian/raspbian/ buster main contrib non-free rpi
[11]
deb http://ftp.cse.yzu.edu.tw/Linux/raspbian/raspbian/ buster main contrib non-free rpi

STEP2: Install Dependencies and Download ROS source packages

$ sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'
$ sudo apt-key adv --keyserver 'hkp://keyserver.ubuntu.com:80' --recv-key C1CF6E31E6BADE8868B172B4F42ED6FBAB17C654
$ sudo apt-get update
$ sudo apt-get install -y python-rosdep python-rosinstall-generator python-wstool pythonrosinstall build-essential cmake

Then initialize rosdep and update it

$ sudo rosdep init
$ rosdep update

STEP3(OPTIONAL): Solve the ERROR:

ERROR :cannot download default sources list from:
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list Website may be down.

• Switch to user directory

$ cd ~

• Download rosditro file

$ git clone https://github.com/ros/rosdistro.git

if Cloning into ‘rosdistro’…
fatal: unable to access ‘https://github.com/ros/rosdistro.git/’: Failed to connect to
github.com port 443: Connection timed out
You can go to this link to download the source package(rosdistro-master.zip) of the master branch. this link is https://github.com/ros/rosdistro.

The download is complete, and then execute the following command：

$ mkdir ~/rosdistro
$ unzip rosdistro-master.zip -d ~/rosdistro
$ mv ~/rosdistro/rosdistro-master/* ~/rosdistro/
$ rm -rf ~/rosdistro/rosdistro-master

When the file is successfully cloned or downloaded, proceed as follows: $ cd ~

• • $ sudo nano ~/rosdistro/rosdep/sources.list.d/20-default.list
    Modify the file as follows:
    Note that ‘pi’ is the user name of the system, you can replace it with your own system user name

# os-specific listings first
#yaml https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/osxhomebrew.yaml osx
yaml file:///home/pi/rosdistro/rosdep/osx-homebrew.yaml osx
# generic
#yaml https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/base.yaml
#yaml https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/python.yaml
#yaml https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/ruby.yaml
#gbpdistro https://raw.githubusercontent.com/ros/rosdistro/master/releases/fuerte.yaml fuerte
yaml file:///home/pi/rosdistro/rosdep/base.yaml
yaml file:///home/pi/rosdistro/rosdep/python.yaml
yaml file:///home/pi/rosdistro/rosdep/ruby.yaml
gbpdistro file:///home/pi/rosdistro/releases/fuerte.yaml fuerte

• • $ sudo nano /usr/lib/python2.7/dist-packages/rosdep2/sources_list.py
    Modify the file as follows:

# default file to download with 'init' command in order to bootstrap
# rosdep
#DEFAULT_SOURCES_LIST_URL ='https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list'
DEFAULT_SOURCES_LIST_URL ='file:///home/pi/rosdistro/rosdep/sources.list.d/20-default.list'
# seconds to wait before aborting download of rosdep data
DOWNLOAD_TIMEOUT = 15.0

• • $ sudo nano /usr/lib/python2.7/dist-packages/rosdep2/rep3.py
    Modify the file as follows:

# location of targets file for processing gbpdistro files
#REP3_TARGETS_URL = 'https://raw.githubusercontent.com/ros/rosdistro/master/releases/targets.yaml'
REP3_TARGETS_URL = 'file:///home/pi/rosdistro/releases/targets.yaml'
# seconds to wait before aborting download of gbpdistro data
DOWNLOAD_TIMEOUT = 15.0

• • $ sudo nano /usr/lib/python2.7/dist-packages/rosdistro/__init__.py
    Modify the file as follows:

# same version as in:
# - setup.py
# - stdeb.cfg
__version__ = '0.8.3'
# index information
#DEFAULT_INDEX_URL ='https://raw.githubusercontent.com/ros/rosdistro/master/index-v4.yaml'
DEFAULT_INDEX_URL = 'file:///home/pi/rosdistro/index-v4.yaml'

• • Then reinitialize rosdep and update it:

$ sudo rosdep init
$ rosdep update

STEP4: Install Melodic Desktop

You need to create a dedicated catkin workspace for building ROS and move to that directory.

$ mkdir ~/ros_catkin_ws
$ cd ~/ros_catkin_ws
$ rosinstall_generator desktop --rosdistro melodic --deps --wet-only --tar > melodic-desktop-wet.rosinstall
$ wstool init -j8 src melodic-desktop-wet.rosinstall

The command will take a few minutes to download all of the core ROS packages into the src folder. If wstool init fails or is interrupted, you can resume the download by running (network access may affect the download of ROS source code, because if you encounter download failures, please try multiple times):

$ wstool update -j4 -t src

STEP5: Fix the Issues

Let’s install the compatible version of Assimp (Open Asset Import Library) to fix collada_urdf dependency problem.

$ mkdir -p ~/ros_catkin_ws/external_src
$ cd ~/ros_catkin_ws/external_src
$ wget https://github.com/assimp/assimp/archive/refs/tags/v5.0.1.zip
$ unzip -o v5.0.1.zip
$ cd assimp-5.0.1
$ cmake .
$ make
$ sudo make install

The user need to install OGRE for rviz ,too

$ sudo apt-get install libogre-1.9-dev

The next step is to use the rosdep tool for installing all the rest of the dependencies:

$ cd ~/ros_catkin_ws
$ rosdep install -y --from-paths src --ignore-src --rosdistro melodic -r --os=debian:buster

STEP6: Build and Source the Installation

Once it has completed downloading the packages and resolving the dependencies you are ready to build the catkin packages. If you’re using raspberry Pi 3, you need to increase the swap size first. If you are using raspberry Pi 4,you can skip this step.

$ sudo mkdir /swap
$ cd /swap
$ sudo dd if=/dev/zero of=swapfile bs=1024 count=2000000
$ sudo mkswap swapfile
$ sudo swapon swapfile

Then build.

$ cd ~/ros_catkin_ws
$ sudo ./src/catkin/bin/catkin_make_isolated --install -DCMAKE_BUILD_TYPE=Release --install-space /opt/ros/melodic -j2

Now ROS Melodic should be installed on your Raspberry Pi 4. We will source the new installation with following command:

$ echo "source /opt/ros/melodic/setup.bash" >> ~/.bashrc
$ source ~/.bashrc

Try launching roscore to check if everything was successful.

$ roscore

3. LiDAR ROS package running demo

3.1 Start Serial ttyS0

$ sudo raspi-config

Open the system configuration interface as shown in the figure below, and select the interface options.
Then select P6 serial.
Then click Yes.
Then Save and exit. Reboot raspberryPi. Please do not disconnect power during reboot. Otherwise, the serial configuration may not take effect.

$ reboot

Check if the serial port is open. View serial port mapping relationship

$ ls -l /dev

Serial0 is the serial port corresponding to the GPIO pin. If you see serial0 connected to ttys0, the serial port configuration is successful.

3.2 Install LiDAR ROS Package

STEP1: Device connection

Connect Lidar and Raspberry Pi 4B as shown in the figure below. 5v connect 5v Power, GND connect Ground, Motor PWM connect BCM18(pwm0),Lidar Uart TX connect BCM15(RXD). Lidar support internal speed control.

• If you want external speed control, you need to download an install the WiringPi library yourself, and configure the BCM18 pin as PWM0, output a 24KHz PWM signal, and implement PID speed control yourself.
• • WiringPi library installation method:
    Then install wiringPi,WiringPi has updated to 2.52 for the Raspberry Pi 4B.

$ cd /tmp
$ wget https://project-downloads.drogon.net/wiringpi-latest.deb
$ sudo dpkg -i wiringpi-latest.deb

• • After wiringPi being updated ,you can check with the latest version update

$ gpio -v

The users need to have the -x permission of raspbian kernel system. After connecting TOF LiDAR_LD06 with raspberry pi 4B/3B/3B+/3A+.

$ sudo chmod 777 /dev/ttyS0

STEP2: ROS DTOF_LiDAR_LD06 Driver Package Compile

The source code of the ROS function package of this product is hosted on the warehouses of Github and Gitee. You can download the source code of the master or main branch by accessing the network link of the warehouse, or download it
through the git tool.

• <1> Warehouse website address:

https://gitee.com/ldrobotSensorTeam/ldlidar_stl_ros

https://github.com/ldrobotSensorTeam/ldlidar_stl_ros

• <2> git download way:

$ cd ~
$ mkdir -p ldlidar_ros_ws/src
$ cd ~/ldlidar_ros_ws/src
$ git clone https://gitee.com/ldrobotSensorTeam/ldlidar_stl_ros.git
# or
$ git clone https://github.com/ldrobotSensorTeam/ldlidar_stl_ros.git

• <3> Modify the port_name value in the ld06.launch file in the ~/ldlidar_ros_ws/src/ldlidar_stl_ros/launch/ directory to /dev/ttyS0

$ nano ~/ldlidar_ros_ws/src/ldlidar_stl_ros/launch/ld06.launch

• <4> Build and Run

$ cd ~/ldlidar_ros_ws
$ catkin_make
$ source devel/setup.bash
$ roslaunch ldlidar_stl_ros ld06.launch

STEP3: RVIZ results

After running the launch file, you need to open a new terminal. Then run rviz to view the scan results, as shown in the following figure:

$ rviz

You need to click the open config button. Then select the ldlidar.rviz file.

4. USE CAUTION

❗️ ALARM: Please connect the TOFLiDAR_LD06 before you power up the raspberry.

• Temperature

  When the working environment temperature of TOFLiDAR_LD06 is too high or too low, it will affect the accuracy of the distance measuring system. It may also damage the structure of the scanning system and reduce the life of the TOFLiDAR_LD06. Avoid use in high temperature (>40 degrees Celsius) and low temperature (<0 degrees Celsius) conditions.

• Ambient lighting

  The ideal working environment for the Lidar is indoor, indoor lighting (including no light) will not affect it work. Don’t using a strong light source (such as a high-power laser) to directly illuminate the lidar’s vision system. If you need to use it outdoors, please avoid that the its vision system is directly facing the sun. This may cause permanent damage to the vision system’s sensor chip,thus invalidating the distance measurement. Please note that the Lidar standard version is subject to interference in outdoor strong sunlight reflection environments.

• Power demand

  For development ,both external adaptor or independent power bank works , but need to ensue 5V and 200MA current power input, for external adaptor solution, the Raspberry Pi SBC adaptor is the preference choose.