text: #include <libopencm3/stm32/rcc.h>
  #include <libopencm3/stm32/gpio.h>
  
  #define PIN_LED	(1<<13)
  
  int main(void) {
  	//rcc_clock_setup_in_hse_8mhz_out_72mhz();
  	rcc_periph_clock_enable(RCC_GPIOC);
  
  	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, PIN_LED);
  	gpio_set(GPIOC, PIN_LED);
  
  	while(1) {
  		gpio_set(GPIOC, PIN_LED);
  		/* wait a little bit */
  		for (int i = 0; i < 80000; i++) {
  			__asm__("nop");
  		}
  		gpio_clear(GPIOC, PIN_LED);
  
  		for (int i = 0; i < 800000; i++) {
  			__asm__("nop");
  		}
  	}
  }
  