#include <Arduino.h>
#define LED_PIN PC13
#define BTN_PIN PA5

volatile bool wakeup = false;

void wakeUp(){
  wakeup = true;
}

void setup(){
  Serial.begin(115200);
  Serial.println("STM32");

  pinMode(LED_PIN, OUTPUT);
  pinMode(BTN_PIN, INPUT_PULLUP);

  attachInterrupt(digitalPinToInterrupt(BTN_PIN), wakeUp, FALLING);
}

void loop(){
  digitalWrite(LED_PIN, LOW);
  Serial.println("LED ON");
  delay(1000);

  digitalWrite(LED_PIN, HIGH);
  Serial.println("LED OFF");
  delay(1000);

  Serial.println("Entering sleep mode");
  wakeup = false;
  while(!wakeup){
  __WFI();
  }
  Serial.println("Woke up!");
}