11. Input devices¶

This week I worked on in reading data from RPLIDAR A1M8-R6 - 360 Degree Laser Scanner

In the following video the LED will LED blink faster when the obstacle get closer to the sensor.

Wiring¶

First I need to wire the RPLidar with my design board which I have made in Electronics Design Week

My Board Pin	RPLidar
FTDI GND	GND
FTDI RX	RX
FTDI TX	TX
VCC	V5.0
GND	GND
FTDI CTS	MOTOCTL
VCC	VMOTO

For programing I wire Arduino UNO board with ISP header of my board

Arduino UNO Pin #	New Board ISP Port
12	1-MISO
5V	2-VCC
13	3-SCK
11	4-MOSI
10	5-RST
GND	6-GND

Here is the full wiring

RPLIDAR library¶

First you’ll need to install the RPLIDAR library from GitHub by download the ZIP file
Export RPLidarDriver folder to Arduino libraries folder

Arduino Code¶

Open Arduino IDE and go to File >> Examples >> RPLidarDriver >> simple_connect
I modify the code by adding the following code

      //perform data processing here...

    if (angle >= 0.0 && angle <= 1.0) {
      if ( distance <= 150 && distance > 100)
        interval = 500;
      else if ( distance <= 100 && distance > 50)
        interval = 100;
      else if ( distance <= 50 && distance >= 0)
        interval = 0;
      else
        interval = 2000;

      timeNow = millis();
      if ( (timeNow - timeOld) >= interval) {
        timeOld = timeNow;
        if (LEDStatus == LOW)
          LEDStatus = HIGH;
        else
          LEDStatus = LOW;
      }
      digitalWrite(pinLED, LEDStatus);
    }

Here is the full code

// This sketch code is based on the RPLIDAR driver library provided by RoboPeak
#include <RPLidar.h>

// You need to create an driver instance
RPLidar lidar;

#define RPLIDAR_MOTOR 2 // The PWM pin for control the speed of RPLIDAR's motor.
// This pin should connected with the RPLIDAR's MOTOCTRL signal


float distanceOld = 0;
unsigned long timeNow = millis();
unsigned long timeOld = millis();
unsigned long interval = 0;
int pinLED = 3;
byte LEDStatus = LOW;

void setup() {
  // bind the RPLIDAR driver to the arduino hardware serial
  lidar.begin(Serial);

  // set pin modes
  pinMode(RPLIDAR_MOTOR, OUTPUT);
  pinMode(pinLED, OUTPUT); // initialize digital pin as an output.
  digitalWrite(pinLED, HIGH);
}

void loop() {
  if (IS_OK(lidar.waitPoint())) {
    float distance = lidar.getCurrentPoint().distance; //distance value in mm unit
    float angle    = lidar.getCurrentPoint().angle; //anglue value in degree
    bool  startBit = lidar.getCurrentPoint().startBit; //whether this point is belong to a new scan
    byte  quality  = lidar.getCurrentPoint().quality; //quality of the current measurement

    //perform data processing here...

    if (angle >= 0.0 && angle <= 1.0) {
      if ( distance <= 150 && distance > 100)
        interval = 500;
      else if ( distance <= 100 && distance > 50)
        interval = 100;
      else if ( distance <= 50 && distance >= 0)
        interval = 0;
      else
        interval = 2000;

      timeNow = millis();
      if ( (timeNow - timeOld) >= interval) {
        timeOld = timeNow;
        if (LEDStatus == LOW)
          LEDStatus = HIGH;
        else
          LEDStatus = LOW;
      }
      digitalWrite(pinLED, LEDStatus);
    }
  } else {
    analogWrite(RPLIDAR_MOTOR, 0); //stop the rplidar motor

    // try to detect RPLIDAR...
    rplidar_response_device_info_t info;
    if (IS_OK(lidar.getDeviceInfo(info, 100))) {
      // detected...
      lidar.startScan();

      // start motor rotating at max allowed speed
      analogWrite(RPLIDAR_MOTOR, 255);
      delay(1000);
    }
  }
}

Testing¶

In the following video the LED will LED blink faster when the obstacle get closer to the sensor.

ROS¶

Useful links¶

Last update: June 16, 2021