/*
// METHODE STANDARD
//#define PORT PA0    // STM32 72mhz => (1.2us) 833khz
#define PORT 7        // UNO   16mhz => (7us) 143khz; MEGA2560 16Mhz => (12us) 83kHz; DUE 84Mhz => (4us) 240khz

void setup() {
  pinMode(PORT, OUTPUT);
}

void loop() {
  digitalWrite(PORT, HIGH);
  digitalWrite(PORT, LOW);
  digitalWrite(PORT, HIGH);
  digitalWrite(PORT, LOW);
}
*/

// METHODE REGISTRE POUR STM32
// STM32 72mhz => (60ns) 18Mhz - !!! la partie non visible (exterieure au loop) dure 474ns

void setup()
{  GPIOA->regs->CRL = 0x33333333; //set PA0-PA7 output
}
void loop()
{  GPIOA->regs->ODR = 0xff;
   GPIOA->regs->ODR = 0x00;
   GPIOA->regs->ODR = 0xff;
   GPIOA->regs->ODR = 0x00;
}