/*
  Pull-down & Pull-up buttons
*/

const int PD_BUTTON_PIN = 8;
const int PU_BUTTON_PIN = 7;

int oldPDval = HIGH;  // pull-down is normally LOW
int oldPUval = LOW;   // pull-up is normally HIGH

void setup() {
  Serial.begin(115200);
  pinMode(PD_BUTTON_PIN, INPUT);        // INPUT needs external resistor
  pinMode(PU_BUTTON_PIN, INPUT_PULLUP); // INPUT_PULLUP doesn't...
  Serial.println("The pull-down button needs Vcc, ground, and an external pull-down resistor.");
  Serial.println("The pull-up button needs only ground, and doesn't need an external resistor.");
  Serial.println("Push a button to see its active state.\n");
}

void loop() {
  int pdVal = digitalRead(PD_BUTTON_PIN);
  int puVal = digitalRead(PU_BUTTON_PIN);

  if (pdVal != oldPDval)  { // if the value changed
    oldPDval = pdVal;       // save the new value
    Serial.print("Pull-down button value: ");
    Serial.println(pdVal ? "HIGH" : "LOW");
    delay(20);  // debounce
  }

  if (puVal != oldPUval)  {
    oldPUval = puVal;
    Serial.print("Pull-up button value: ");
    Serial.println(puVal ? "HIGH" : "LOW");
    delay(20);  // debounce
  }
}