main.cpp

#include <Arduino.h>

long randNumber;

void setup() {
  Serial.begin(9600);
  pinMode(D4, OUTPUT); // NodeMCU: D4, Lolin32: LED_BUILTIN
  randomSeed(analogRead(0));
}

void loop() {
  randNumber = random(10, 20);
  Serial.println(randNumber);
  digitalWrite(D4, HIGH); // remember to change this for Lolin32
  delay(1000);
  digitalWrite(D4, LOW);  // remember to change this for Lolin32
  delay(1000);
}