const int BTN_PD_PIN = 9;
const int BTN_PU_PIN = 8;

int oldPDVal = LOW;
int oldPUVal = HIGH;

void setup() {
  Serial.begin(115200);
  pinMode(BTN_PD_PIN, INPUT);
  pinMode(BTN_PU_PIN, INPUT_PULLUP);
}

void loop() {
  int pdValue = digitalRead(BTN_PD_PIN);
  if (pdValue != oldPDVal)  {
    oldPDVal = pdValue;
    if (pdValue == HIGH)  {
      Serial.println("Pull down pressed.");
    }
    delay(20);
  }

  int puValue = digitalRead(BTN_PU_PIN);
  if (puValue != oldPUVal)  {
    oldPUVal = puValue;
    if (puValue == LOW)  {
      Serial.println("Pull up pressed.");
    }
    delay(20);
  }

}