Charlieplex_LEDs_Arduino

arduino_charlieplex.c

/**************************************/
/* Charlieplexing 6 LEDs with 3 Pins  */
/*                                    */
/* Code written by William Hart, 2011 */
/* http://www.williamhart.info        */
/*                                    */
/* Uses 3 pins to power a network of  */
/* 6 LEDs using the charlieplexing    */
/* technique.                         */ 
/**************************************/

#define LED_A 5
#define LED_B 6
#define LED_C 7
 
void setup()
{
  // first set all pins to input, or high impedance
  // (not strictly necessary as all pins are inputs by default)
  pinMode(LED_A, INPUT);
  pinMode(LED_B, INPUT);
  pinMode(LED_C, INPUT);
}
 
void loop()
{
  // run through a sample loop, lighting each LED
 
  // in turn and holding for half a second.
  set_pins(LED_A, LED_B);
  delay(100);

  set_pins(LED_B, LED_A);
  delay(100);
 
  set_pins(LED_C, LED_A); 
  delay(100);
 
  set_pins(LED_A, LED_C);
  delay(100);

  set_pins(LED_B, LED_C);
  delay(100);
 
  set_pins(LED_C, LED_B);
  delay(100); 
}

void set_pins(int high_pin, int low_pin)
{
  // reset all the pins
  reset_pins();
 
  // set the high and low pins to output
  pinMode(high_pin, OUTPUT);
  pinMode(low_pin, OUTPUT);
 
  // set high pin to logic high, low to logic low
  digitalWrite(high_pin, HIGH);
  digitalWrite(low_pin,LOW);
}

void reset_pins()
{
  // start by ensuring all pins are at input and low
  pinMode(LED_A, INPUT); 
  pinMode(LED_B, INPUT);
  pinMode(LED_C, INPUT);

  digitalWrite(LED_A, LOW);
  digitalWrite(LED_B, LOW);
  digitalWrite(LED_C, LOW);
}