Energia Reference - Tutorials

Examples > Control Structures

Switch (case) Statement, used with sensor input

Switch statements allow mulitple choices in which sections of code to run for a given conditional.

Hardware Required

MSP430 LaunchPad
(5) LEDs
(5) 220 ohm resistors
breadboard
hook-up wire

Relevant Groundwork

An if statement allows you to choose between two discrete options, TRUE or FALSE. When there are more than two options, you can use multiple if statements, or you can use the switch statement. Switch allows you to choose between several discrete options.

This tutorial shows you how to use switch to turn on one of several different LEDs based on a byte of data received serially. The sketch listens for serial input, and turns on a different LED for the characters a, b, c, d, or e.

Five LEDs are attached to digital pins 2, 3, 4, 5, and 6 in series through 220 ohm resistors.

To make this sketch work, your LaunchPad must be connected to your computer. Open the Serial Monitor, and send the characters a, b, c, d, or e, or anything else.

Circuit

image developed using Fritzing. For more circuit examples, see the Fritzing project page

Schematic:

Code Explanation

None.

Code

/*
  Switch statement  with serial input
 
  Demonstrates the use of a switch statement.  The switch
  statement allows you to choose from among a set of discrete values
  of a variable.  It's like a series of if statements.
 
  To see this sketch in action, open the Serial monitor and send any character.
  The characters a, b, c, d, and e, will turn on LEDs.  Any other character will turn
  the LEDs off.
 
  The circuit:
  * 5 LEDs attached to digital pins 2 through 6 through 220-ohm resistors
 
  created 1 Jul 2009
  by Tom Igoe 
  modified 30 Apr 2013
  by Adrian Fernandez 
 
  This example code is in the public domain.
   
 */

void setup() {
  // initialize serial communication:
  Serial.begin(9600); 
  // initialize the LED pins:
  for (int thisPin = 2; thisPin < 7; thisPin++) {
    pinMode(thisPin, OUTPUT);
  } 
}

void loop() {
  // read the sensor:
  if (Serial.available() > 0) {
    int inByte = Serial.read();
    // do something different depending on the character received.  
    // The switch statement expects single number values for each case;
    // in this exmaple, though, you're using single quotes to tell
    // the controller to get the ASCII value for the character.  For 
    // example 'a' = 97, 'b' = 98, and so forth:

    switch (inByte) {
    case 'a':    
      digitalWrite(2, HIGH);
      break;
    case 'b':    
      digitalWrite(3, HIGH);
      break;
    case 'c':    
      digitalWrite(4, HIGH);
      break;
    case 'd':    
      digitalWrite(5, HIGH);
      break;
    case 'e':    
      digitalWrite(6, HIGH);
      break;
    default:
      // turn all the LEDs off:
      for (int thisPin = 2; thisPin < 7; thisPin++) {
        digitalWrite(thisPin, LOW);
      }
    } 
  }
}

Working Video

(Insert Video Here)

Try it out:

- use a switch case to integrate with a button