void setup() { PORTA.DIR |= 0b00010000;//portA 4pin(Arduino 0 pin)is OUTPUT } void loop() { PORTA.OUT |= 0b00010000;//portA 4pin(Arduino 0 pin)is HIGH delay(1000); PORTA.OUT &= ~0b00010000;//portA 4pin(Arduino 0 pin)is LOW delay(1000); }