//Blink
void setup() {
 // initialize digital pin LED_BUILTIN as an output.
 pinMode(LED_BUILTIN, OUTPUT);
}
// the loop function runs over and over again forever
void loop() {
 digitalWrite(LED_BUILTIN, HIGH); // turn the LED on (HIGH is the voltage level)
 delay(1000); // wait for a second
 digitalWrite(LED_BUILTIN, LOW); // turn the LED off by making the voltage LOW
 delay(1000); // wait for a second
}