timer_set_oc_value(TIM4, TIM_OC2, T4_CYCLE / 2);
timer_set_oc_polarity_high(TIM4, TIM_OC2);
timer_enable_oc_output(TIM4, TIM_OC2);
timer_set_oc_value(TIM4, TIM_OC2, T4_CYCLE / 2);
timer_set_oc_polarity_high(TIM4, TIM_OC2);
timer_enable_oc_output(TIM4, TIM_OC2);