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WritingLidarTutorial(c++)

Description: This tutorial covers how to write a lidar tutorial in C++. Tutorial Level: BEGINNER Next Tutorial: Examining the simple lidar tutorial

Table of Contents

Writing a Simple lidar tutorial (C++)

Description: This tutorial covers how to write a LiDAR data console program in C++. Tutorial Level: BEGINNER

create beginner_tutorials directories

mkdir beginner_tutorials
cd beginner_tutorials

Create the lidar_tutorial.cpp file within the beginner_tutorials project and paste the following inside it:

https://github.com/YDLIDAR/ydlidar_tutorials/blob/master/cpp_tutorials/lidar_tutorial/lidar_tutorial.cpp

#include "CYdLidar.h"
#include <string>
using namespace std;
using namespace ydlidar;

#if defined(_MSC_VER)
#pragma comment(lib, "ydlidar_sdk.lib")
#endif

int main(int argc, char *argv[]) {
  // init system signal
  ydlidar::os_init();

  CYdLidar laser;
  //////////////////////string property/////////////////
  /// Lidar ports
  std::map<std::string, std::string> ports = ydlidar::lidarPortList();
  std::string port = "/dev/ydlidar";
  if(!ports.empty()) {
      port = ports.begin()->second;
  }
  /// lidar port
  laser.setlidaropt(LidarPropSerialPort, port.c_str(), port.size());
  /// ignore array
  std::string ignore_array;
  ignore_array.clear();
  laser.setlidaropt(LidarPropIgnoreArray, ignore_array.c_str(),
                    ignore_array.size());

  //////////////////////int property/////////////////
  /// lidar baudrate
  int optval = 230400;
  laser.setlidaropt(LidarPropSerialBaudrate, &optval, sizeof(int));
  /// tof lidar
  optval = TYPE_TRIANGLE;
  laser.setlidaropt(LidarPropLidarType, &optval, sizeof(int));
  /// device type
  optval = YDLIDAR_TYPE_SERIAL;
  laser.setlidaropt(LidarPropDeviceType, &optval, sizeof(int));
  /// sample rate
  optval = 9;
  laser.setlidaropt(LidarPropSampleRate, &optval, sizeof(int));
  /// abnormal count
  optval = 4;
  laser.setlidaropt(LidarPropAbnormalCheckCount, &optval, sizeof(int));

  //////////////////////bool property/////////////////
  /// fixed angle resolution
  bool b_optvalue = false;
  laser.setlidaropt(LidarPropFixedResolution, &b_optvalue, sizeof(bool));
  /// rotate 180
  laser.setlidaropt(LidarPropReversion, &b_optvalue, sizeof(bool));
  /// Counterclockwise
  laser.setlidaropt(LidarPropInverted, &b_optvalue, sizeof(bool));
  b_optvalue = true;
  laser.setlidaropt(LidarPropAutoReconnect, &b_optvalue, sizeof(bool));
  /// one-way communication
  b_optvalue = false;
  laser.setlidaropt(LidarPropSingleChannel, &b_optvalue, sizeof(bool));
  /// intensity
  b_optvalue = false;
  laser.setlidaropt(LidarPropIntenstiy, &b_optvalue, sizeof(bool));
  /// Motor DTR
  b_optvalue = false;
  laser.setlidaropt(LidarPropSupportMotorDtrCtrl, &b_optvalue, sizeof(bool));
  /// HeartBeat
  b_optvalue = false;
  laser.setlidaropt(LidarPropSupportHeartBeat, &b_optvalue, sizeof(bool));


  //////////////////////float property/////////////////
  /// unit: °
  float f_optvalue = 180.0f;
  laser.setlidaropt(LidarPropMaxAngle, &f_optvalue, sizeof(float));
  f_optvalue = -180.0f;
  laser.setlidaropt(LidarPropMinAngle, &f_optvalue, sizeof(float));
  /// unit: m
  f_optvalue = 16.f;
  laser.setlidaropt(LidarPropMaxRange, &f_optvalue, sizeof(float));
  f_optvalue = 0.1f;
  laser.setlidaropt(LidarPropMinRange, &f_optvalue, sizeof(float));
  /// unit: Hz
  f_optvalue = 10.f;
  laser.setlidaropt(LidarPropScanFrequency, &f_optvalue, sizeof(float));

  // initialize SDK and LiDAR
  bool ret = laser.initialize();
  if (ret) {//success
    //Start the device scanning routine which runs on a separate thread and enable motor.
    ret = laser.turnOn();
  } else {
    fprintf(stderr, "%s\n", laser.DescribeError());
    fflush(stderr);
  }

  // Turn On success and loop  
  while (ret && ydlidar::os_isOk()) {
    LaserScan scan;
    if (laser.doProcessSimple(scan)) {
      fprintf(stdout, "Scan received[%llu]: %u ranges is [%f]Hz\n",
              scan.stamp,
              (unsigned int)scan.points.size(), 1.0 / scan.config.scan_time);
      fflush(stdout);
    } else {
      fprintf(stderr, "Failed to get Lidar Data\n");
      fflush(stderr);
    }
  }
  // Stop the device scanning thread and disable motor.
  laser.turnOff();
  // Uninitialize the SDK and Disconnect the LiDAR.
  laser.disconnecting();
  return 0;
}

The Code Explained

Now, let's break the code down.

#include "CYdLidar.h"

CYdLidar.h is a convenience include that includes all the headers necessary to use the most common public pieces of the YDLIDAR SDK.

  ydlidar::os_init();

Initialize system signal. install a SIGINT handler which provides Ctrl-C handling

  CYdLidar laser;

Create a handle to this Lidar.

 //////////////////////string property/////////////////
  /// Lidar ports
  std::map<std::string, std::string> ports = ydlidar::lidarPortList();
  std::string port = "/dev/ydlidar";
  if(!ports.empty()) {
      port = ports.begin()->second;
  }

Query avaliable Lidar ports.

  /// lidar port
  laser.setlidaropt(LidarPropSerialPort, port.c_str(), port.size());
  /// ignore array
  std::string ignore_array;
  ignore_array.clear();
  laser.setlidaropt(LidarPropIgnoreArray, ignore_array.c_str(),
                    ignore_array.size());

Set Lidar string property paramters.

  //////////////////////int property/////////////////
  /// lidar baudrate
  int optval = 230400;
  laser.setlidaropt(LidarPropSerialBaudrate, &optval, sizeof(int));
  /// tof lidar
  optval = TYPE_TRIANGLE;
  laser.setlidaropt(LidarPropLidarType, &optval, sizeof(int));
  /// device type
  optval = YDLIDAR_TYPE_SERIAL;
  laser.setlidaropt(LidarPropDeviceType, &optval, sizeof(int));
  /// sample rate
  optval = 9;
  laser.setlidaropt(LidarPropSampleRate, &optval, sizeof(int));
  /// abnormal count
  optval = 4;
  laser.setlidaropt(LidarPropAbnormalCheckCount, &optval, sizeof(int));

Set Lidar string int paramters.

  //////////////////////bool property/////////////////
  /// fixed angle resolution
  bool b_optvalue = false;
  laser.setlidaropt(LidarPropFixedResolution, &b_optvalue, sizeof(bool));
  /// rotate 180
  laser.setlidaropt(LidarPropReversion, &b_optvalue, sizeof(bool));
  /// Counterclockwise
  laser.setlidaropt(LidarPropInverted, &b_optvalue, sizeof(bool));
  b_optvalue = true;
  laser.setlidaropt(LidarPropAutoReconnect, &b_optvalue, sizeof(bool));
  /// one-way communication
  b_optvalue = false;
  laser.setlidaropt(LidarPropSingleChannel, &b_optvalue, sizeof(bool));
  /// intensity
  b_optvalue = false;
  laser.setlidaropt(LidarPropIntenstiy, &b_optvalue, sizeof(bool));
  /// Motor DTR
  b_optvalue = false;
  laser.setlidaropt(LidarPropSupportMotorDtrCtrl, &b_optvalue, sizeof(bool));

Set Lidar bool property paramters.

  //////////////////////float property/////////////////
  /// unit: °
  float f_optvalue = 180.0f;
  laser.setlidaropt(LidarPropMaxAngle, &f_optvalue, sizeof(float));
  f_optvalue = -180.0f;
  laser.setlidaropt(LidarPropMinAngle, &f_optvalue, sizeof(float));
  /// unit: m
  f_optvalue = 16.f;
  laser.setlidaropt(LidarPropMaxRange, &f_optvalue, sizeof(float));
  f_optvalue = 0.1f;
  laser.setlidaropt(LidarPropMinRange, &f_optvalue, sizeof(float));
  /// unit: Hz
  f_optvalue = 10.f;
  laser.setlidaropt(LidarPropScanFrequency, &f_optvalue, sizeof(float));

Set Lidar float property paramters.

  // initialize SDK and LiDAR
  bool ret = laser.initialize();

Initialize the SDK and LiDAR.

initialize will return false if:

  • Serial port does not correspond to the actual Lidar.
  • Serial port does not have read and write permissions.
  • Lidar baud rate settings error.
  • Incorrect Lidar type setting.
  if (ret) {//success
    //Start the device scanning routine which runs on a separate thread and enable motor.
    ret = laser.turnOn();
  } else {
    fprintf(stderr, "%s\n", laser.DescribeError());
    fflush(stderr);
  }

Start the device scanning routine which runs on a separate thread and enable motor.

turnOn will return false if:

  • Lidar stall.
  • Lidar power suppy is unstable.
  // Turn On success and loop  
  while (ret && ydlidar::os_isOk()) {

By ydlidar::os_init() will install a SIGINT handler which provides Ctrl-C handling which will cause ydlidar::os_isOk() to return false if that happens.

ydlidar::os_isOk() will return false if:

  • a SIGINT is received (Ctrl-C)
  • ydlidar::os_shutdown() has been called by another part of the application.

Once ydlidar::os_isOk() returns false, Loop exit.

    LaserScan scan;
    if (laser.doProcessSimple(scan)) {
      fprintf(stdout, "Scan received[%llu]: %u ranges is [%f]Hz\n",
              scan.stamp,
              (unsigned int)scan.points.size(), 1.0 / scan.config.scan_time);
      fflush(stdout);
    } else {
      fprintf(stderr, "Failed to get Lidar Data\n");
      fflush(stderr);
    }

Get the LiDAR Scan Data.

  // Stop the device scanning thread and disable motor.
  laser.turnOff();

Stop the device scanning thread and disable motor.

  // Uninitialize the SDK and Disconnect the LiDAR.
  laser.disconnecting();

Uninitialize the SDK and Disconnect the LiDAR.

Building your project

You need to create a CMakeLists.txt file.

The generated CMakeLists.txt should look like this: https://github.com/YDLIDAR/ydlidar_tutorials/blob/master/cpp_tutorials/lidar_tutorial/CMakeLists.txt

cmake_minimum_required(VERSION 2.8)
PROJECT(lidar_tutorial)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
add_definitions(-std=c++11) # Use C++11


#Include directories
include_directories(
     ${CMAKE_SOURCE_DIR}
)
############## YDLIDAR SDK START#####################################
#find ydlidar_sdk package
find_package(ydlidar_sdk REQUIRED)
#Include directories
include_directories(
  ${YDLIDAR_SDK_INCLUDE_DIRS}
)

#link library directories
link_directories(${YDLIDAR_SDK_LIBRARY_DIRS})

add_executable(${PROJECT_NAME} lidar_tutorial.cpp)

#Link your project to ydlidar_sdk library.
target_link_libraries(${PROJECT_NAME} ${YDLIDAR_SDK_LIBRARIES})

############## YDLIDAR SDK END#####################################

This will create one executable, lidar_tutorial, which by default will go into package directory of your build space.

Linux:

  • YDLIDAR_SDK_LIBRARIES includes ydlidar_sdk pthread rt
  • If you need the pthread library at the end of the compilation flag, you need to put YDLIDAR_SDK_LIBRARIES at the end.

you can use the following variable to depend on all necessary targets:

target_link_libraries(${PROJECT_NAME} ${YDLIDAR_SDK_LIBRARIES})

Now run cmake:

# In your project directory
mkdir build
cd build
cmake ..
make j4

Now that you have written a simple lidar tutorial, let's examine the simple lidar tutorial.