Infinite “while” statement

Question

I am building a robot that is both obstacle-avoiding and remote-controlled. The robot uses an infrared remote. When the front button is pressed the robot moves front, when the right button is pressed the robot turns right, and so on...
When a certain button is pressed the robot switches to obstacle-avoiding mode and starts to drive around. When the ultrasonic sensor detects an object 15cm away the robot turns right, reverses, and then continues moving forward. the obstacle-avoiding code has a problem, though. Here is the code:

#include <EEPROM.h>
#include <IRLib.h>
#include <AFMotor.h>
int frontlights = A1;
int backlights = A2;
int buzzer = A3;
int pingPin = A4; //setup pingpin as A4  

//ir variables
int RECV_PIN = A0;
IRrecv My_Receiver(RECV_PIN);
IRdecode My_Decoder;
unsigned int Buffer[RAWBUF];  

void obstacle_avoiding(){
   while (My_Decoder.value==0xFF807F && My_Decoder.value!=0xFF0AF5){  // when the automatic mode button is pressed and the stop button is not pressed do...  

 motor4.setSpeed(230);
 motor3.setSpeed(230);
 motor2.setSpeed(230); 
 motor1.setSpeed(230);

    long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);

  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();
  delay(90);

      if(cm>15){          // if an object is greater than 10cm move forward
      motor_forward();
      Serial.println("forward");
      digitalWrite(backlights, LOW);

      }


     else if (cm<=15)     // if an object is less than or equal 10cm move backward then turn right 
     {
      motor_stop();
      digitalWrite(frontlights, HIGH);
      digitalWrite(backlights, HIGH);
      digitalWrite(buzzer, HIGH);
      delay(200);
      digitalWrite(buzzer, LOW);
      delay(2000);
      motor_backward();
      digitalWrite(backlights, HIGH);
      Serial.println("backward");
      delay(500);
      motor_stop();
      digitalWrite(backlights, HIGH);
      delay(900);
      motor_right();
      digitalWrite(backlights, LOW);
      Serial.println("right");
      digitalWrite(frontlights, LOW);
      delay(400);

   }
   if (My_Decoder.value==0xFF0AF5){   //the stop button is pressed break the "while" loop and stop the robot 
   break;
   motor_stop();
   }
 }
}  



void loop() {
   long duration, inches, cm;
    if (My_Receiver.GetResults(&My_Decoder)){
       //Restart the receiver so it can be capturing another code
       //while we are working on decoding this one.
       My_Receiver.resume(); 
       My_Decoder.decode();

    //automatic code here
            else if (My_Decoder.value==0xFF807F && My_Decoder.value!=0xFF0AF5){
              obstacle_avoiding();   

            } 

          }

        }  

The code is working however when the "while" statement becomes true it will loop infinitely not stopping even when the condition has become false. I thought while statements should loop until the condition becomes false. Am I misinformed?

Answer 1

My_Decoder.value doesn't change inside obstacle_avoiding(). Hence, while is running infinitely.

I think you have to delete the while, and let loop() take care of controlling the execution.

Addendum

The intent of the loop() is to read some IR data in value. I under the impression that getResults() sometimes block, acording to this:

However the IRrecvLoop is not interrupt driven and so when you call GetResults it sits in a tight loop and does not release control back to you until the complete signal has been received.

I also want to check that value doesn't change if getResults() return nothing with this loop()

void loop() {
bool r = My_Receiver.GetResults(&My_Decoder)
Serial.print("getResults()=");
Serial.print(r);
Serial.print(" value=");
Serial.println(My_Decoder.value);

if (r) {
    //Restart the receiver so it can be capturing another code
    //while we are working on decoding this one.
    My_Receiver.resume();
    My_Decoder.decode();
} else {
    if (My_Decoder.value == 0xFF807F && My_Decoder.value != 0xFF0AF5) {
        obstacle_avoiding();
        }
    }
}

I hope this works!

Answer 2

Copy/paste this part only:

void loop() {
   long duration, inches, cm;
    if (My_Receiver.GetResults(&My_Decoder)){
       //Restart the receiver so it can be capturing another code
       //while we are working on decoding this one.
       My_Receiver.resume(); 
       My_Decoder.decode();
        }
    //automatic code here
           if (My_Decoder.value==0xFF807F && My_Decoder.value!=0xFF0AF5){
              obstacle_avoiding();   

            } 

          }

        }