#include "system.h"
#include "gpio.h"
////////////////////////////////////////////////////////////////////////
static constexpr unsigned ticks   = SYSTEM_CORE_CLOCK / 1000u;
static volatile  unsigned counter = 0u;
extern "C" [[gnu::interrupt]] void SysTick_Handler ();
////////////////////////////////////////////////////////////////////////
void SysTick_Handler () {
  SysTick.SR = 0u;
  if (counter) counter -= 1u;
}
static void delay (const unsigned dly = 200u) {
  counter = dly;
  while (counter);
}

int main () {
  GpioClass led  (GPIOB, 8);
  SysTick.Config (ticks);
  unsigned pass_cnt = 0u;
  for (;;) {
    delay();
    const bool b = pass_cnt & 1u;
    led << b;
    pass_cnt += 1u;
  }
  return 0;
}