TIM: Down counter with interrupts

Set timer to count down to 300ms, from 4800 to 0 counts, and trigger an interrupt on every underflow.

#include "bsp.h"

int main( void )
{
    TIM_HandleTypeDef TIM_Handler;    /*TIM initial structure*/
    
    HAL_Init();                                     /*Init HAL library*/
    __HAL_RCC_TIM1_CLK_ENABLE();                   /*Enable clock on TIM1*/

    /*configure timer 1 with a preescaler of 1000 and starting count of 4800
    by default the timer get a Tfrec of 16MHz from the APB bus*/
    TIM_Handler.Instance = TIM1;                          /*Timer TIM to configure*/
    TIM_Handler.Init.Prescaler = 1000;                    /*preescaler Tfrec / Prescaler*/
    TIM_Handler.Init.CounterMode = TIM_COUNTERMODE_DOWN;  /*count from Period value to zero*/
    TIM_Handler.Init.Period = 4800;                       /*down count from 4800*/
    /*use the previous parameters to set configuration on TIM1*/
    HAL_TIM_Base_Init( &TIM_Handler );
    
    /*Enable interrupt vector TIM1_BRK_UP_TRG_COM_IRQ where the CPU will jump in any of 
    the following events: TIM1 Break, Update, Trigger and Commutation */
    HAL_NVIC_SetPriority( TIM1_BRK_UP_TRG_COM_IRQn, 2, 0 );/*se fija la prioridad a nivel 2*/
    HAL_NVIC_EnableIRQ( TIM1_BRK_UP_TRG_COM_IRQn );

    /*init the timer count from oveflow value (4800  in this case) and trigger an interrupts*/
    HAL_TIM_Base_Start_IT( &TIM_Handler );

    while (1)
    {
        /*Do nothing*/
    }
}

/* when the timer TIm1 reaches its count down to zero this function will be called by HAL_GPIO_EXTI_IRQHandler
which is in turn called from the TIM1_BRK_UP_TRG_COM_IRQHandler interrupt vector*/
void HAL_TIM_PeriodElapsedCallback( TIM_HandleTypeDef *htim )
{
    /*This code will reached every 300ms according to TIM1 configuration and the formula:
    Period = 300ms / (Preeescaler / Tfrec)
    Perios = 300ms / (1000 / 16MHz) = 4800*/    
}

ints.c

/*it is necesary to make a reference to TIM structure*/
extern TIM_HandleTypeDef TIM_Handler;

/*Declare interrupt service rutine as it is declare in startup_stm32g0b1xx.s file*/
void TIM1_BRK_UP_TRG_COM_IRQHandler( void )
{
    /*HAL library function that attend interrupt on TIM timers
    this fucntion amount other things will clear the timer flag and the corresponding 
    callback functio*/
    HAL_TIM_IRQHandler( &TIM_Handler );
}