#define ENCODER_A 25
#define ENCODER_B  26

//Encoder counter
volatile int counter;

ICACHE_RAM_ATTR void ISRENCODER_A()
{ 
  if(digitalRead(ENCODER_B) )
    counter++;

}

ICACHE_RAM_ATTR void ISRENCODER_B()
{
  if( digitalRead(ENCODER_A))
    counter--;

}

void setup() {
  Serial.begin(115200);
  pinMode(ENCODER_A, INPUT);
  pinMode(ENCODER_B, INPUT);

  attachInterrupt(digitalPinToInterrupt(ENCODER_A), ISRENCODER_A, FALLING);
  attachInterrupt(digitalPinToInterrupt(ENCODER_B), ISRENCODER_B, FALLING);

  counter = 0;
}

int lastClk = HIGH;

void loop() {
  //Escritura puerto serie  
  Serial.println(counter);
  
  delay(100);        // delay in between reads for stability
}