Make the LED blink as a hello world

main.ino

@@ -0,0 +1,25 @@
+#define RELAY_PIN 12
+#define LED_PIN 13
+
+void setup() {
+  Serial.begin(115200);
+
+  Serial.println("START");
+
+  pinMode(LED_PIN, OUTPUT);
+
+}
+
+void loop() {
+
+  digitalWrite(LED_PIN, HIGH);
+
+  delay(1000);
+
+  digitalWrite(LED_PIN, LOW);
+
+  delay(1000);
+
+  Serial.println("LED");
+
+}