[Timer] Add set prescaler register function

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Author: Tjeerdie

cores/arduino/stm32/timer.c

@@ -1086,6 +1086,17 @@ uint32_t getCCRRegister(stimer_t *obj, uint32_t channel)
  return __HAL_TIM_GET_COMPARE(&(obj->handle), channel);
 }
 
+/**
+ * @brief Set the TIM Capture Compare Register value.
+ * @param timer_id : id of the timer
+ * @param prescaler : prescaler value to set for this timer.
+ * @retval None
+ */
+void setTimerPrescalerRegister(stimer_t *obj, uint32_t prescaler)
+{
+ __HAL_TIM_SET_PRESCALER(&(obj->handle), prescaler);
+}
+
 /**
  * @brief Attached an interrupt handler
  * @param timer_id : id of the timer

cores/arduino/stm32/timer.h

@@ -214,6 +214,7 @@ uint32_t getTimerCounter(stimer_t *obj);
 void setTimerCounter(stimer_t *obj, uint32_t value);
 void setCCRRegister(stimer_t *obj, uint32_t channel, uint32_t value);
 uint32_t getCCRRegister(stimer_t *obj, uint32_t channel);
+void setTimerPrescalerRegister(stimer_t *obj, uint32_t prescaler);
 
 uint32_t getTimerIrq(TIM_TypeDef *tim);
 uint8_t getTimerClkSrc(TIM_TypeDef *tim);