• Paul Badger 2007
• RandomWalk wanders up and down randomly between two
• endpoints. The maximum move in one loop is governed by
• the parameter "stepsize".
• A static variable is moved up and down a random amount.
• This technique is also known as "pink noise" and "drunken walk".
• /

  Serial.println(thisTime);
   delay(10);

                         // values in between function calls, but no other functions can change its value

 RandomWalk wanders up and down randomly between two

endpoints. The maximum move in one loop is governed by the parameter "stepsize".

 A static variable is moved up and down a random amount.

This technique is also known as "pink noise" and "drunken walk".

/* RandomWalk

 Paul Badger 2007
 RandomWalk wanders up and down randomly between two endpoints. The maximum move in one loop is governed by the parameter "stepsize".
 A static variable is moved up and down a random amount. This technique is also known as "pink noise" and "drunken walk".
 */

1. define randomWalkLowRange -20
2. define randomWalkHighRange 20

int stepsize;

int thisTime; int total;

void setup() {

  Serial.begin(9600);
  Serial.println("start ");

}

void loop() { // tetst randomWalk function

  stepsize = 5;
  thisTime = randomWalk(stepsize);
  total += thisTime;                  // aggregate values to see if function is really random
  Serial.print(thisTime);
  Serial.print("  ");
  Serial.println(total);
  delay(10);

}

int randomWalk(int moveSize){

  static int  place;     // variable to store value in random walk - declared static so that it stores
                         // values in between function calls, but no other functions can mess with its value

  place = place + (random(-moveSize, moveSize + 1));

  if (place < randomWalkLowRange){                    // check lower and upper limits
    place = place + (randomWalkLowRange - place);     // reflect number back in positive direction
  }
  else if(place > randomWalkHighRange){
    place = place - (place - randomWalkHighRange);     // reflect number back in negative direction
  }

  return place;

}

@]

Static

The static keyword is used to create variables that are visible to only one function. However unlike local variables that get created and destroyed every time a function is called, static variables persist beyond the function call, preserving their data between function calls.

Variables declared as static will only be created and initialized the first time a function is called.

Example

[@