#include <stm32f10x_lib.h>                 // STM32F10x Library Definitions

/*----------------------------------------------------------------------------
   Wait function - delay flashing
*---------------------------------------------------------------------------*/
void wait (void) {
  unsigned int countDown = 300000;         // arbitrary int to count down

  while(countDown--);                      // count down
}

/*----------------------------------------------------------------------------
   MAIN function
*---------------------------------------------------------------------------*/
int main (void) {
  unsigned int leds = 0x01;                // declare and init LEDs

  while (1) {                              // Loop forever
    if (leds > 0x8000) (leds = 0x01);      // check for max value
    GPIOB->ODR = leds;                     // defined in library
    leds <<= 0x1;                          // shift
    wait();                                // delay flashing
  }
}