#define GPIO_PIN 5
unit32_t freq=0;
void setup()
{
  pinMode(GPIO_PIN, OUTPUT);
  Serial.begin(115200);
  setupfrequencyMhz(10);
  freq=getCPUfrequencyMhz();
  Serial.print("CPU Freq= ");
  Serial.print(freq);
  Serial.println("Mhz");
  freq=getXTALFrequencyMhz();
  Serial.print("XTAL Freq= ");
  Serial.print(freq);
  Serial.print("MHZ");
  Freq=getApb frequency();
  Serial.print("APB Freq= ");
  Serial.print(freq);
  Serial.print("Hz");
}
void loop()
{
  digitalWrite(GPIO_PIN,1);
  digitalWrite(GPIO_PIN,0);
}