DodgeBot

Forum 2005-2010 (read only) Software Troubleshooting
1

Hi,

I need help. I trying to learn how to program the arduino. I am currently involved in making a dodging robot. I am using 4 ping sensors to detect the distances. After detecting that, I do a comparison between the distances to find out which one is the farthest, then the corresponding direction PIN is set to HIGH. The problem is that this code is executing very slowly. I was wondering if any changes could be made to the code to make it execute fast. Right now its taking almost 5 seconds to output a HIGH.
please help! I got some of this code in the forum.

int ultraSoundSignalPins[] = {2,3,4,5}; // Left,Front, Front Right, Rear Ultrasound signal pins
char *pingString[] = {"Left ","Front ", "Right ", "Rear "}; // just something to print to indicate direction
int farthest_Dist=ping(0);
int pinFWD=7;
int pinREAR=8;
int pinLEFT=9;
int pinRIGHT=10;

void setup()
{

Serial.begin(9600);
pinMode(pinFWD,OUTPUT);
pinMode(pinREAR,OUTPUT);
pinMode(pinLEFT,OUTPUT);
pinMode(pinRIGHT,OUTPUT);
}

void loop()
{

unsigned long ultrasoundValue;
for(int i=0; i < 4; i++)
{
ultrasoundValue = ping(i);
Serial.print(pingString*);*

  • Serial.print(ultrasoundValue);*

  • Serial.print("in, "); *

  • Serial.println();*

  • }*

  • {*

  • {*

  • if (ping(1) > ping(0))*

  • {*

  • farthest_Dist=ping(1);*

  • digitalWrite(pinFWD,HIGH);*

  • }*

  • else if (ping(2)>ping(0))*

  • {*

  • farthest_Dist=ping(2);*

  • digitalWrite(pinRIGHT,HIGH);*

  • }*

  • else if (ping(3) > ping(0))*

  • {*

  • farthest_Dist=ping(3);*

  • digitalWrite(pinREAR,HIGH);*

  • }*

  • else if (ping(0)==ping(1)==ping(2)==ping(3))*

  • {*

  • digitalWrite(pinLEFT,LOW);*

  • digitalWrite(pinFWD,LOW);*

  • digitalWrite(pinRIGHT,LOW);*

  • digitalWrite(pinREAR,LOW);*

  • }*

  • else*

  • {*

  • farthest_Dist = ping(0);*

  • digitalWrite(pinLEFT,HIGH);*

  • }*

Serial.print (farthest_Dist);

  • Serial.println();*
  • }*
  • }*

}
//Ping function
unsigned long ping(int i)
{

  • unsigned long echo;*
    _ pinMode(ultraSoundSignalPins*, OUTPUT); // Switch signalpin to output*_
    _ digitalWrite(ultraSoundSignalPins*, LOW); // Send low pulse*
    * delayMicroseconds(2); // Wait for 2 microseconds*
    digitalWrite(ultraSoundSignalPins*, HIGH); // Send high pulse*
    * delayMicroseconds(5); // Wait for 5 microseconds*
    digitalWrite(ultraSoundSignalPins*, LOW); // Holdoff*
    pinMode(ultraSoundSignalPins*, INPUT); // Switch signalpin to input*
    digitalWrite(ultraSoundSignalPins*, HIGH); // Turn on pullup resistor*
    echo = pulseIn(ultraSoundSignalPins*, HIGH); //Listen for echo*
    return (echo / 58.138) * .39; //convert to CM then to inches_
    }
2

The problem is that this code is executing very slowly

I doubt it. It's executing at whatever clock speed your processor is configured for.

its taking almost 5 seconds to output a HIGH

That's a two second improvement on your other post - what did you change?

Please don't cross-post.

unsigned long ultrasoundValue;
 for(int i=0; i < 4; i++)
 {
   ultrasoundValue = ping(i);
   Serial.print(pingString[i]);
   Serial.print(ultrasoundValue);
   Serial.print("in, ");    
   Serial.println();
   
 }

Why bother printing the same value four times with different labels?

Instead of stuff like this:

if (ping(1) > ping(0))
    {
      farthest_Dist=ping(1);

you'd probably be better off collecting the four readings in an array and using those values than repeatedly calling "ping"

3

Following Groove's suggestion, and using an array of readings, taken once per pass, will speed things up considerably.

Floating point arithmetic is not the Arduino's strong suit, especially division.

Change this code to do one multiplication instead of a division and a multiplication to improve performance, too.

return (echo / 58.138) * .39; //convert to CM then to inches
4

Thank you. I will try this. Sorry for cross-posting. I agree with you. I think calling for ping again and again is slowing the process. Please explain. How do i collect the values in an array and then compare?
Once again I greatly appreciate your help. I will also decrease the calculation PaulS.

5

How do i collect the values in an array and then compare?

int ultraVals[4];

void loop()
{
    for(byte i=0; i<4; i++)
    {
        ultraVals[i] = ping(i);
    }

    // Now, use ultraVals[i] instead of ping(i) for the rest of the loop
}