Arduino入門：乱数

//Arduino Sketch Example: randomSeed
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
random(value)

//Parameters
//long, int - pass a number to generate the seed.

//Description
/*
randomSeed() initializes the pseudo-random number generator, causing it to start at an arbitrary point in its random sequence. This sequence, while very long, and random, is always the same.
If it is important for a sequence of values generated by random() to differ, on subsequent executions of a sketch, use randomSeed() to initialize the random number generator with a fairly random input, such as analogRead() on an unconnected pin.
Conversely, it can occasionally be useful to use pseudo-random sequences that repeat exactly. This can be accomplished by calling randomSeed() with a fixed number, before starting the random sequence.
*/

//Example

long randNumber;

void setup(){
  Serial.begin(9600);
  randomSeed(analogRead(0));
}

void loop(){
  randNumber = random(300);
  Serial.println(randNumber);

  delay(50);
}

//Arduino Sketch Example: random
//Date: 2015.1.18
//Edited and Modified by: easy labo
//Original Source: Arduino Reference (http://arduino.cc/en/Reference/HomePage)

//Syntax
random(max)
random(min, max)

//Parameters
//min - lower bound of the random value, inclusive (optional)
//max - upper bound of the random value, exclusive

//Returns
//a random number between min and max-1 (long)

//Description
//The random function generates pseudo-random numbers.

//Note:
/*
If it is important for a sequence of values generated by random() to differ, on subsequent executions of a sketch, use randomSeed() to initialize the random number generator with a fairly random input, such as analogRead() on an unconnected pin.
Conversely, it can occasionally be useful to use pseudo-random sequences that repeat exactly. This can be accomplished by calling randomSeed() with a fixed number, before starting the random sequence.
*/

//Example

long randNumber;

void setup(){
  Serial.begin(9600);

  // if analog input pin 0 is unconnected, random analog
  // noise will cause the call to randomSeed() to generate
  // different seed numbers each time the sketch runs.
  // randomSeed() will then shuffle the random function.
  randomSeed(analogRead(0));
}

void loop() {
  // print a random number from 0 to 299
  randNumber = random(300);
  Serial.println(randNumber);  

  // print a random number from 10 to 19
  randNumber = random(10, 20);
  Serial.println(randNumber);

  delay(50);
}