#define BTN_RED 25  
#define BTN_GREEN 26
#define LED_PIN    2 

// variables will change:
int led_state = LOW;    // the current state of LED
int btn_red;       // the current state of button
int btn_green = LOW;

void setup() {
    // put your setup code here, to run once:
    Serial.begin(115200);
    Serial.write("Giữ nút đỏ để dừng đèn led");
    Serial.write("Giữ nút xanh để thay đổi tần suất sáng đèn led");
    pinMode(LED_PIN, OUTPUT);
    pinMode(BTN_RED, INPUT_PULLUP);
    pinMode(BTN_GREEN, INPUT_PULLUP);
    btn_red = digitalRead(BTN_RED);
}

void loop() {
    btn_red = digitalRead(BTN_RED);
    if(btn_red == HIGH){   
      btn_green = digitalRead(BTN_GREEN); // read new state
      if (btn_green == HIGH) {
        digitalWrite(LED_PIN, HIGH);
        delay(3000);
        digitalWrite(LED_PIN, LOW);
        delay(1000);
      }else{
        digitalWrite(LED_PIN, HIGH);
        delay(500);
        digitalWrite(LED_PIN, LOW);
        delay(500);
      }
    }
    else{
      digitalWrite(LED_PIN, LOW);
      
    }
}