Arduino demo: State machine with push buttons and LEDs

This is a short presentation of a demo where I implement a simple state machine using an Arduino, a push button and three LEDs.

The state machine goes to he next state whenever a push button is pressed. The trigger can be anything, such as a specific reading from a sensor and the state can perform any action desired.

To keep this demo simple I just used a push button to cycle through 3 LEDs where the first state turns them all off and each progressive state turns them on, one by one.

Sketch:

/*


   Connect the positive side of your LED to Arduino digital pin 13
   Connect the negative side of your LED to a 330 Ohm resistor
   Connect the other side of the resistor to ground

*/


// First we'll set up constants for the pin numbers.
// This will make it easier to follow the code below.

const int button1Pin = 2;  // pushbutton 1 pin
const int led1Pin =  13;    // LED 1 pin
const int led2Pin =  12;    // LED 2 pin
const int led3Pin =  11;    // LED 3 pin

int iState;
bool bWasPressed;  //Variable to see if the buton was pressed

void setup()
{
 // Set up the pushbutton pins to be an input:
 pinMode(button1Pin, INPUT);

 // Set up the LED pin to be an output:
 pinMode(led1Pin, OUTPUT);      
 pinMode(led2Pin, OUTPUT);      
 pinMode(led3Pin, OUTPUT);      

 //Default to state 0
 iState = 0;  
 bWasPressed = false;

 // initialize serial communication at 9600 bits per second:
// Serial.begin(9600);

}


void loop()
{
 int iBtnState;  // variable to hold the pushbutton state
 

 // iBtnState:  HIGH = button not pressed
 //             LOW = button is pushed


 iBtnState = digitalRead(button1Pin);

 //Now determine whether I need to change state.
 if (iBtnState == 1)  
 {
   //The button is not pressed. If the button was just
   //released then go on ahead to the next state.
   if (bWasPressed==1)
     {
       //Yes, the button was just released.
       //Move to the next state.
       iState++;
       
       iState = iState % 4;
       
       //Reset the button pressed flag.
       bWasPressed = false;
     }
 }
 else
 {
   //The button is pressed, just set the flag.    
   bWasPressed = true;
 }

 //Take action depending on the state of the machine.
 switch (iState)
 {
   case 0:
     //Turn off all LEDs
     digitalWrite(led1Pin, LOW);
     digitalWrite(led2Pin, LOW);
     digitalWrite(led3Pin, LOW);
     break;
   case 1:
     //Turn on first LED
     digitalWrite(led1Pin, HIGH);
     break;
   case 2:
     //Turn on second LED
     digitalWrite(led2Pin, HIGH);
     break;
   case 3:
     //Turn on third LED
     digitalWrite(led3Pin, HIGH);
     break;
 }

}

• #howto_style
• #arduino_brand
• #led
• #push_button
• #state_machine
• #demo
• #sgvdemo