Arduino blinking led example but fixed to work also on boards with less PIN, ie attiny85 #arduino #c

universal_blinking_led_arduino_example.ino

#include <Arduino.h>

// Attiny85 doesn't have nor recognize LED_BUILTIN 13 from Arduino.h
// Little fix to enable led blink with a LED on PIN 3 + GND to test boards. 
#ifndef LED_BUILTIN
#define LED_BUILTIN 3
#endif

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  Serial.begin(9600);
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.write(LED_BUILTIN + "\n");
}

// 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
}