iRobot Create2+Arduino: Make the robot stop when facing an obstacle

Question

I have been working on writing a code to control the iRobot Create movements (forward, backward, right, left and stop) from serial monitor and finally I got the correct code. I was trying to understand how to make stop moving when it face an obstacle but I couldn't get it. Also, I didn't know how to make move for a specific distance. Could anyone help me with this?

Here is my code:

#include "Arduino.h"
#include "Morse.h"
#include <SoftwareSerial.h>
#define rxPin 10
#define txPin 11
SoftwareSerial softSerial = SoftwareSerial(rxPin, txPin);
char inByte = 0; // incoming serial byte

irobot::irobot(int pin)
{
  pinMode(pin, OUTPUT);
  _pin = pin;
}


void irobot::Begin()
{
   delay(2000); // Needed to let the robot initialize
// define pin modes for software tx, rx pins:
 pinMode(rxPin, INPUT);
 pinMode(txPin, OUTPUT);
// start the the SoftwareSerial port 19200 bps (robotís default)
 softSerial.begin(19200);
// start hardware serial port
Serial.begin(19200);
softSerial.write(128); // This command starts the OI.
softSerial.write(131); // set mode to safe (see p.7 of OI manual)
delay(2000);
}

void irobot::runIt()
{
    softSerial.write(142); // requests the OI to send a packet of
    // sensor data bytes
    softSerial.write(9); // request cliff sensor value specifically
    delay(250); // poll sensor 4 times a second
    if (Serial.available() > 0) {
        inByte = Serial.read();
        if(inByte == '8')
        {
            goForward();
        }
        if(inByte == '2'){
            goBackward();
        }
        if(inByte == '4')
            goLeft();
        if(inByte == '6')
            goRight();
        if(inByte == '5')
            stop();
    }
    Serial.println(inByte);
}


void irobot::goForward()
{
   // Drive op code
    softSerial.write(137);
    // Velocity (-500 ñ 500 mm/s)
    softSerial.write((byte)0);
    softSerial.write((byte)200);
    //Radius (-2000 - 2000 mm)
    softSerial.write((byte)128);
    softSerial.write((byte)0);
}



void irobot::goBackward()
{
    // Drive op code
    softSerial.write(137);
    // Velocity (-500 ñ 500 mm/s)
    softSerial.write(255);
    softSerial.write(56);
    //Radius (-2000 - 2000 mm)
    softSerial.write((byte)128);
    softSerial.write((byte)0);
}



void irobot::goLeft()
{
    // Drive op code
    softSerial.write(137);
    // Velocity (-500 ñ 500 mm/s)
    softSerial.write((byte)0);
    softSerial.write((byte)200);
    //Radius (-2000 - 2000 mm)
    softSerial.write((byte)0);
    softSerial.write((byte)1);
}


void irobot::goRight()
{
    // Drive op code
    softSerial.write(137);
    // Velocity (-500 ñ 500 mm/s)
    softSerial.write((byte)0);
    softSerial.write((byte)200);
    //Radius (-2000 - 2000 mm)
    softSerial.write((byte)255);
    softSerial.write((byte)255);
}

void irobot::stop()
{
    softSerial.write(137);
    softSerial.write((byte)0);
    softSerial.write((byte)0);
    //Radius (-2000 - 2000 mm)
    softSerial.write((byte)0);
    softSerial.write((byte)0);
}

Answer 1

All you need is a ultrasonic sensor to detect objects. You can buy one at aliexpress. Then you must download a library named NewPing Arduino Library for Arduino which is compatible with a wide range of ultrasonic sensors.

You can download it from Arduino New Ping at Bitbucket.

It contains functions to take distance between the sensor and the obstacle. Then you can set a condition using if statement that of the distance between the obstacle and robot is less than, say, 5 CM, then stop all motors. For more information consult instuctables website.

Answer 2

You can use the roombas' bumper and light bumper(infrared) sensors to slow down or completely avoid an object. Note: It won't work on surfaces that don't reflect light. Edit: You can use its wheel encoders to know how far it has gone.