static

1/* RandomWalk
2      Paul Badger 2007
3      RandomWalk wanders up and down randomly between two
4      endpoints. The maximum move in one loop is governed by
5      the parameter "stepsize".
6      A static variable is moved up and down a random amount.
7      This technique is also known as "pink noise" and "drunken walk".
8    */
9
10    #define randomWalkLowRange -20
11    #define randomWalkHighRange 20
12    int stepsize;
13
14    int thisTime;
15
16    void setup() {
17      Serial.begin(9600);
18    }
19
20    void loop() {
21      //  test randomWalk function
22      stepsize = 5;
23      thisTime = randomWalk(stepsize);
24      Serial.println(thisTime);
25      delay(10);
26    }
27
28    int randomWalk(int moveSize) {
29      static int place; // variable to store value in random walk - declared static so that it stores
30      // values in between function calls, but no other functions can change its value
31
32      place = place + (random(-moveSize, moveSize + 1));
33
34      if (place < randomWalkLowRange) {                               // check lower and upper limits
35        place = randomWalkLowRange + (randomWalkLowRange - place);    // reflect number back in positive direction
36      }
37      else if (place > randomWalkHighRange) {
38        place = randomWalkHighRange - (place - randomWalkHighRange);  // reflect number back in negative direction
39      }
40
41      return place;
42    }