Volatile variable is not updated in ISR in STM32F429 in Keil - stm32

Question

I am struggling with getting the value from Timer interrupt in STM32F429. I am using Keil. The HAL I am using is not the one from CubeMX but it is old version library. Due to some reasons, I must continue to work in this library.
I have declared the counter value in interrupt as "volatile". But the value I get is rubbish or it is not increasing.
The timer 4 is set to run execute ISR as 1us.
To verify it, I have toggled GPIOA Pin 1. And it toggles at 1us interval. But I need to up count variable "time4_tick" and it is not increasing.
I put two delays of 1000 ms and 2000 ms between start and stop of Timer 4. The count is not updating properly. I declared the variable volatile to not optimize it but it didn't solve my problem. Looks like something unknown is going here.
My code is below. What could be the problem here.
/********** Timer 4 interrupt *******/
__IO uint64_t time4_tick = 0;
void Sys_Timer4(void) // 1us
{
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE);
TIM_Cmd(TIM4, DISABLE);
TIM_ITConfig(TIM4, TIM_IT_Update, DISABLE); // Enable TIM3 Update interrupt
TIM_TimeBaseStructure.TIM_Period = 21-1; //
TIM_TimeBaseStructure.TIM_Prescaler = 4-1; // 21*4/84 MHz = 1 usec
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure);
TIM_SetCounter(TIM4,0);
TIM_Cmd(TIM4, ENABLE);
TIM_ClearITPendingBit(TIM4, TIM_IT_Update); //Added this
TIM_ITConfig(TIM4, TIM_IT_Update, ENABLE); // Enable TIM2 Update interrupt
// Enable the TIM4 Interrupt
NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
}
/********** Timer 4 IRQ Handler*******/
void TIM4_IRQHandler(void)
{
if (TIM_GetITStatus(TIM4, TIM_IT_Update) != RESET)
{
TIM_ClearITPendingBit(TIM4, TIM_IT_Update);
time4_tick++;
GPIO_ToggleBits(GPIOA, GPIO_Pin_1);
}
}
/********** Main program loop *******/
int main(void)
{
// Other initializations
while(1)
{
TIM_Cmd(TIM4, ENABLE);
Delay_ms(1000);
TIM_Cmd(TIM4, DISABLE);
dbgmsg("time4_tick 1: %d\n", time4_tick);
time4_tick = 0;
TIM_Cmd(TIM4, ENABLE);
Delay_ms(2000);
TIM_Cmd(TIM4, DISABLE);
dbgmsg("time4_tick 2: %d\n", time4_tick);
time4_tick = 0;
// Other tasks
}
}
time4_tick should have different values after delay of 1000 ms and 2000 ms but it is showing same value. What is the problem here ?

Answer 1

dbgmsg("time4_tick 1: %d\n", time4_tick);
time4_tick = 0;
You zero it every time. Delete this line, then check. If it does not update then it means that the interrupt handler was not invoked.