Good afternoon everyone....
I am trying to learn more about the stm32 and am using a nucleo L476 and an oscilloscope. In particular I want to understand more about the output compares of the timers. I have read many an app-note , user guide and data sheet regarding these and am now at the stage of testing stuff out.....I am running into complete confusion with respect to this...
I have a 26MHz clock with a prescaler of 26 -1 (should be a 1MHz Cnt clock). I have the ARR register loaded with 100 - 1 (should create an UIF event every 100us). I am using CubeMX to set this up. There are a few questions:
- I had to code the macro (see below) bcz CubeMx doesn't seem to check the UIE bit when setting up as compare output.....Can anyone comment as to why?
__HAL_TIM_ENABLE_IT(&htim3, TIM_IT_UPDATE);The following below is my ISR.....My attempt was to have UIF interrupt me every 10khz (see above comment on this), turn the output on and arm the CCR with counter + 10. My thought was that after this expires (CNTR clock is 1MHz so my expectation was 10us later) I would get a CC1R interrupt and then clear the output using FORCED_ACTIVE and INACTIVE statements. There are a few things here:
- I notice with breakpoints set neither the macro nor the call after it clear the UIF flag....Why is this??(I have attached pic below showing enables or IRQs set and flags set
- I never get into the CC1 portion of the interrupt...any thoughts as to why?? as the expression solves to a '1'
- Where do I find the various priorities of the flags that can cause an interrupt in TIMER3?? is the UIE higher priority than the CCxE?
void HAL_TIM_OC_DelayElapsedCallback(TIM_HandleTypeDef *htim)
{
if (htim == &htim3)
{
if(htim->Channel == HAL_TIM_ACTIVE_CHANNEL_1)
{
if (__HAL_TIM_GET_FLAG(htim, TIM_FLAG_CC1))
{
__HAL_TIM_CLEAR_FLAG(htim, TIM_IT_CC1);
htim->Instance->SR &= ~TIM_SR_CC1IF;
htim->Instance->CCR1 = 0;
htim->Instance->CCMR1 = 0; //clears mode output bits --- freezes output
htim->Instance->CCMR1 |= TIM_OCMODE_FORCED_INACTIVE; //forces output to 0??
}
else if (__HAL_TIM_GET_FLAG(htim, TIM_FLAG_UPDATE))
{
__HAL_TIM_CLEAR_FLAG(htim, TIM_IT_UPDATE); //clear UIF Flag
htim->Instance->SR &= ~TIM_SR_UIF;
htim->Instance->CCR1 = htim->Instance->CNT + 10;
htim->Instance->CCMR1 = 0; //clears mode output bits --- freezes output
htim->Instance->CCMR1 |= TIM_OCMODE_FORCED_ACTIVE; //set output to 1 immediately
}
}
}
}
Notice ONLY CC1IE enabled.
htim3.Instance->DIER |= TIM_DIER_CC1IE;
htim3.Instance->CCR1 = 1000;
htim3.Instance->CR1 |= TIM_CR1_CEN;Setup for htim3 (done via cubeMX):
htim3.Instance = TIM3;
htim3.Init.Prescaler = 0;
htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
htim3.Init.Period = 20000 - 1;
htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_ENABLE;
if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
{
Error_Handler();
}
sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
{
Error_Handler();
}
if (HAL_TIM_OC_Init(&htim3) != HAL_OK)
{
Error_Handler();
}
sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
{
Error_Handler();
}
sConfigOC.OCMode = TIM_OCMODE_TIMING;
sConfigOC.Pulse = 0;
sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;The ISR that does it all:
void TIM3_IRQHandler(void)
{
if (htim3.Instance->SR & TIM_SR_CC1IF)
{
htim3.Instance->SR = ~TIM_SR_CC1IF;
htim3.Instance->CCR1 = htim3.Instance->CNT + 1000;
HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
}
}