/* -------------------------------------------------------- *
Arduino register control

Ports: {
  B: gpio 7-0,
  D: gpio 13-8,
  C: adc 5-0
}

Registers: {
  DDRx: set input/output,
  PORTx: write low/high,
  PINx: read low/high
}

PinMap: {
  Pxn: {x: Porta, n: Pino},
  PB5: 13 (LED_BUILTIN),
  PD4: 4 (gpio),
  PC0: 0 (A0),
}

/* -------------------------------------------------------- */
void setup() {
  Serial.begin(9600);

  /* --------------- pinMode --------------- */
  DDRB |= (1 << PB5); // set ledPin: output
  DDRD &= ~(1 << PD4); // set buttonPin: input
}

/* -------------------------------------------------------- */
void loop() {

  /* --------------- digitalWrite --------------- */
  //PORTB |= (1 << PB5);  // high
  //PORTB &= ~(1 << PB5); // low
  PORTB ^= (1 << PB5);  // toggle
  
  /* --------------- digitalRead --------------- */
  //printBinary(PINB, 5);
  printBinary(PIND, 8);
  
  /* --------------- executionControl --------------- */
  //while(1);
  delay(5000);
}

/* -------------------------------------------------------- */
void printBinary(byte reg, size_t numberOfBits) {
  for (size_t i = 0; i < numberOfBits; i++) {
    size_t thisBit = numberOfBits - i; // decrement index
    bool bitValue = (reg & (1 << thisBit));
    Serial.print(bitValue);
  }
  Serial.print("\n");
}

/* -------------------------------------------------------- */