C

void setup_timer(void) {
    rcc_periph_clock_enable(RCC_TIM3);
    timer_reset(TIM3);
    timer_set_mode(TIM3, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
    timer_set_prescaler(TIM3, 0);
    timer_set_clock_division(TIM3, 0);
    timer_set_period(TIM3, PERIOD);
    timer_set_oc_mode(TIM3, TIM_OC1, TIM_OCM_PWM1);
    timer_set_oc_polarity_high(TIM3, TIM_OC1);
/*    timer_set_dma_on_compare_event(TIM3);*/
    timer_set_master_mode(TIM3, TIM_CCMR1_OC1M_PWM1);
    timer_enable_oc_output(TIM3, TIM_OC1);
    timer_enable_counter(TIM3);
}