/* Configuration function */
void timer_config(void)
{
    TIM_TimeBaseInitTypeDef tim;
    NVIC_InitTypeDef nvic;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_TIM9, ENABLE);

#ifdef 1
    /* Results in a period of 10.33 ms */
    tim.TIM_Prescaler = 59999;
    tim.TIM_Period = 28;
#else
    /* Results in a period of 10.007 ms */
    tim.TIM_Prescaler = 1249;
    tim.TIM_Period = 1344;
#endif
    tim.TIM_CounterMode = TIM_CounterMode_Up;
    tim.TIM_ClockDivision = TIM_CKD_DIV1;
    TIM_TimeBaseInit(TIM9, &tim);

    nvic.NVIC_IRQChannel =                      TIM1_BRK_TIM9_IRQn;
    nvic.NVIC_IRQChannelPreemptionPriority =    0;
    nvic.NVIC_IRQChannelSubPriority =           0;
    nvic.NVIC_IRQChannelCmd =                   ENABLE;
    NVIC_Init(&nvic);

    TIM_ITConfig(TIM9, TIM_IT_Update, ENABLE);
    TIM_Cmd(TIM9, ENABLE);
}

/* TIM9 ISR */
void TIM1_BRK_TIM9_IRQHandler(void)
{
        GPIOC->ODR |= GPIO_Pin_0;

        TIM9->SR &= ~TIM_IT_Update;

    /* Minor ISR operations. Only array access and subtractions */

        GPIOC->ODR &= ~GPIO_Pin_0;
}