platformio-core/examples/wiring-blink/src/main.cpp

#ifdef ENERGIA
	#include "Energia.h"
#else
	#include "Arduino.h"
#endif

#ifndef LED_PIN
	// Most Arduino boards already have a LED attached to pin 13 on the board itself
	#define LED_PIN 13
#endif

void setup() {
  pinMode(LED_PIN, OUTPUT);     // set pin as output
}

void loop() {
  digitalWrite(LED_PIN, HIGH);  // set the LED on
  delay(1000);                  // wait for a second
  digitalWrite(LED_PIN, LOW);   // set the LED off
  delay(1000);                  // wait for a second
}