softwareCharlieplexing.ino

#define A 3
#define B 4
#define C 5
#define D 6
#define E 7

int matrix[4][4][2] =
{
  { {A, B}, {C, B}, {D, B}, {E, B} },
  { {A, C}, {B, C}, {D, C}, {E, C} },
  { {A, D}, {B, D}, {C, D}, {E, D} },
  { {A, E}, {B, E}, {C, E}, {D, E} }
};

int frameBuffer[4][4];

int charlieIdxX = 0;
int charlieIdxY = 0;

void setup()
{
  for( int yIdx = 0; yIdx < 4; yIdx++ )  
  { for( int xIdx = 0; xIdx < 4; xIdx++ )
    {
      frameBuffer[yIdx][xIdx] = 0;
    }
  }
  
  frameBuffer[1][0] = 1; // test
  frameBuffer[3][2] = 1;
 
  // initialize timer1 
  noInterrupts();           // disable all interrupts
  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1  = 0;

  OCR1A = 4000;             // compare match register 16MHz/256/2Hz
  TCCR1B |= (1 << WGM12);   // CTC mode
  TCCR1B |= (1 << CS10);
  TIMSK1 |= (1 << OCIE1A);  // enable timer compare interrupt
  interrupts();             // enable all interrupts

}

void modGlobalCharlieIdx() {
  charlieIdxX++;
  
  if(charlieIdxX == 4) {
    charlieIdxX = 0;
    charlieIdxY++;
  }
  
  if(charlieIdxY == 4) {
    charlieIdxX = 0;
    charlieIdxY = 0;
  }
}

void resetCherliplexing() {
  pinMode( A, INPUT );
  pinMode( B, INPUT );
  pinMode( C, INPUT );
  pinMode( D, INPUT );
  pinMode( E, INPUT );
}

void light( int pins[2] )
{
  pinMode( pins[0], OUTPUT );
  digitalWrite( pins[0], HIGH );

  pinMode( pins[1], OUTPUT );
  digitalWrite( pins[1], LOW );
}

ISR(TIMER1_COMPA_vect)          // timer compare interrupt service routine
{
  resetCherliplexing();
  
  if( frameBuffer[charlieIdxY][charlieIdxX])
  { light( matrix[charlieIdxY][charlieIdxX] ); }
  
  modGlobalCharlieIdx();
}

void loop()
{
  ;
}