/*
// ESP8266
const int in  = D1; // nodeMCU
const int out = D2; // nodeMCU
*/

/*
// ATtiny412
const int in  = 3;
const int out = 2; 
*/


// STM32
const int in  = 8;
const int out = 7; 


void setup() {
  pinMode(in, INPUT);
  pinMode(out, OUTPUT);
  delay(100);
  digitalWrite(out, HIGH);
  delay(1000);
}

void loop() {
  // ESP8266 tries to do WiFi stuff at the start of each void loop() 
  // this while loop prevents that happening
  //while (1){ 
    digitalWrite(out, 1-digitalRead(in));    
  //}
  
}