#define GPIO_pin 5
uint32_t Freq=0;

void setup()
{
  pinMode(GPIO_pin,OUTPUT);
  Serial.begin(115200);
  Freq=getCpuFrequencyMhz();
  Serial.print("CPU Freq=");
  Serial.print(Freq);
  Serial.println("MHz");
  Freq=getXtalFrequencyMhz();
  Serial.print("XTAL Freq=");
  Serial.print(Freq);
  Serial.println("MHz");
  Freq=getApbFrequency();
  Serial.print("APB Frequency");
  Serial.print(Freq);
  Serial.println("Hz");
}
void loop(){
  digitalWrite(GPIO_pin,1);
  digitalWrite(GPIO_pin,0);
}