// Define the 3 pins used for Charlieplexing
const int pins[] = {2, 3, 4}; 
const int NUM_PINS = 3;
const int NUM_LEDS = NUM_PINS * (NUM_PINS - 1); // 6

// Array to hold the state of each LED (0 = off, 1 = on)
int led_state[NUM_LEDS] = {1, 0, 1, 0, 1, 0}; // Example: LEDs 1, 3, and 5 are ON

// Structure to define the wiring connections
// Source Pin (HIGH), Sink Pin (LOW)
const int led_connections[NUM_LEDS][2] = {
  {0, 1}, // LED 1: Pin 2 (HIGH) -> Pin 3 (LOW)
  {1, 0}, // LED 2: Pin 3 (HIGH) -> Pin 2 (LOW)
  {0, 2}, // LED 3: Pin 2 (HIGH) -> Pin 4 (LOW)
  {2, 0}, // LED 4: Pin 4 (HIGH) -> Pin 2 (LOW)
  {1, 2}, // LED 5: Pin 3 (HIGH) -> Pin 4 (LOW)
  {2, 1}  // LED 6: Pin 4 (HIGH) -> Pin 3 (LOW)
};

// Function to light up a single LED
void setLED(int ledIndex) {
  // 1. Get the source and sink pin indexes from the table
  int sourcePinIndex = led_connections[ledIndex][0];
  int sinkPinIndex = led_connections[ledIndex][1];
  
  // The third pin is the "inactive" pin
  int inactivePinIndex = 3 - sourcePinIndex - sinkPinIndex; 

  // 2. Set all pins back to INPUT mode (safest neutral state)
  for (int i = 0; i < NUM_PINS; i++) {
    pinMode(pins[i], INPUT);
  }

  // 3. Configure the active path
  // Source Pin: Set to HIGH Output
  pinMode(pins[sourcePinIndex], OUTPUT);
  digitalWrite(pins[sourcePinIndex], HIGH);

  // Sink Pin: Set to LOW Output (Ground)
  pinMode(pins[sinkPinIndex], OUTPUT);
  digitalWrite(pins[sinkPinIndex], LOW);
  
  // The inactive pin remains in INPUT mode (High Impedance)
}


void setup() {
  // All pins are initialized as INPUT by default in the setLED function
}


void loop() {
  // Multiplexing loop: Quickly cycle through all LEDs
  for (int i = 0; i < NUM_LEDS; i++) {
    if (led_state[i] == 1) {
      setLED(i);
      // Brief delay for the LED to be visible. 
      // The total cycle time (6 * delay) should be less than ~20ms.
      delayMicroseconds(2000); // 2 milliseconds (2ms * 6 LEDs = 12ms cycle time)
    }
  }
}

// Example function to make the LEDs "chase"
void chase() {
  for (int i = 0; i < NUM_LEDS; i++) {
    // Turn off all LEDs
    for(int j=0; j<NUM_LEDS; j++) led_state[j] = 0;
    
    // Turn on the current LED
    led_state[i] = 1;

    // Run the display loop for a short time
    for (int k = 0; k < 50; k++) { // 50 cycles of the display loop
      for (int l = 0; l < NUM_LEDS; l++) {
        if (led_state[l] == 1) {
          setLED(l);
          delayMicroseconds(2000);
        }
      }
    }
  }
}

// To use the chase effect, replace the loop() content with:
/* void loop() {
  chase();
}
*/