Monday, November 8, 2010

Arduino Day 8: “Reaction” Game

Tip! This post is part of a series on my adventures with Arduino

Today’s build combines a lot of the skills I’ve learned so far. It’s a simple game you’ve probably played before. It works like this for two players (though any number is possible):

  1. Each player gets a clicker
  2. When the buzzer sounds and the center light illuminates, hit our clicker as fast as you can
  3. The first player to click wins

Here’s the finished project:

I don’t have anything to rant about today so I’ll instead direct you to this rather entertaining interview with David Sedaris. If you don’t know who that is, you probably won’t find it funny. In that case, this type of humor probably more your style.




The circuit and code are completely from scratch, but they are so simple I wouldn’t be surprised to find a near duplicate elsewhere. Note that the buttons are on opposite sides of the board on purpose: this is a two player game.




The schematic makes this thing look insane. I suggest just looking at the circuit above—it’s really a simple build.



const int ToneHz = 2000;
const int P1ButtonPin = 3;
const int P1LedPin = 4;
const int BuzzPin = 5;
const int P2LedPin = 6;
const int P2ButtonPin = 7;
const int BuzzDuration = 100; 

void setup() {
  pinMode(P1LedPin, OUTPUT);
  pinMode(BuzzPin, OUTPUT);
  pinMode(P2LedPin, OUTPUT);
  // boot test
  digitalWrite(P1LedPin, HIGH);
  digitalWrite(P1LedPin, LOW);
  digitalWrite(P2LedPin, HIGH);
  digitalWrite(P2LedPin, LOW);
  Buzz(ToneHz, BuzzDuration * 2);

// our main loop will look at the game state to 
// figure out what to do. when the state's not changing,
// things like buzzing or reading input will occur
// repeatedly, very fast

enum GameState {
 InsertCoin, // waiting for player to start game
 Pounce,     // about to buzz (sleeping random amount)
 Bzzzzz,     // buzzing (waiting for button)
 Woohoo      // player 1 or 2 pressed first

// randomly start with p1 or p2
int Victor = random(1,3);

// start in the finished state because that sets up some things for us
GameState State = Woohoo;

void loop() {
  // these pins get reference a lot so just figure it out at the beginning
  int LastWinnerLedPin = Victor == 1? P1LedPin : P2LedPin;
  int LastWinnerButtonPin = Victor == 1? P1ButtonPin : P2ButtonPin;

  int P1; int P2;
    case InsertCoin:
        // let's go!
        digitalWrite(LastWinnerLedPin, LOW); 
        State = Pounce;
    case Pounce:
      State = Bzzzzz;
      // don't buzz for 1-7 seconds (the suspense is intense)
    case Bzzzzz:
      Buzz(ToneHz, BuzzDuration / 5);
      P1 = digitalRead(P1ButtonPin);
      P2 = digitalRead(P2ButtonPin);
      if(P1 || P2){
        // note the victor and move on to the next state
        // I suppose this gives a teeny advantage to player 1 since it gets checked first
        Victor = P1? 1 : 2;
        State = Woohoo;
    case Woohoo:
      // light up the victor
      digitalWrite(LastWinnerLedPin, HIGH);
      // pseudo debouce
      // signal a victory
      // go back to idle
      State = InsertCoin;

void Buzz(int frequencyHz, int durationMillis){
  // e.g. 1 / 2048Hz = 488uS, or 244uS high and 244uS low
  // to create 50% duty cycle
  int Osc = 1000000 / frequencyHz / 2; // in microseconds
  // compute the number of iterations needed to hold
  // the nfote the desired duration
  int Iterations = frequencyHz * ((float)durationMillis / 1000);
  for (long i = 0; i < Iterations; i++ )
      // beep!
      digitalWrite(BuzzPin, HIGH);
      digitalWrite(BuzzPin, LOW);

void BlinkAFewTimes(int pin){

void BlinkOnce(int pin){
  digitalWrite(pin, LOW); 
  digitalWrite(pin, HIGH); 

Next Steps

While this project could certainly be improved (e.g. holding down your button insures victory when instead you should lose for pressing it early), I’m satisfied with it.

I might try to build a Simon game tomorrow. Special thanks to @corsae for a nice list of project ideas.