Is it possible to trigger an event with the same timer used for a PWM generation?

[JGreg.2]

Hello,

Working on STM32F030R8 nucleo board, using MXcube, i am trying to use the same timer as the one who is used to generate a PWM output.

For this, i am used to use HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef* htim) with if(htim->Instance == TIM1) but nothing happens whereas it does for other timer with the same settings.

Maybe the way to used the same timer event is different because already used for PWM, is it ?

Thank you,

[waclawek.jan]

TIM1 is different from other timers in that it has a separate interrupt for Capture/Compare, and a different one for Update and other events. Make sure you have enabled the latter (TIM1_BRK_UP_TRG_COM_IRQn) and that the ISR is appropriately named, too.

Also read out and check the TIM registers, mainly if TIM1_DIER.UIE is set.

JW

[JGreg.2]

Hello Waclawek.jan and thank you for your answer.

(TIM1_BRK_UP_TRG_COM_IRQn) was already enable.

I have set the UIE bit of TIM1_DIER which i did not found configured at all, but it changes nothing.

And what do you mean by "the ISR is approriately nammed" ?

As i was worknig exclusively with HAL functions thanks to CubeMX and i was not really understanding the fundamental aspect of the way it works, i have decided to run through the datasheet (DMA, Interrupts and Events, ADC and finally timers chapters) in order to have the knowledge for what i need in my project.

My english is not my native language and as i am quite new in STM32 microcontroller, i have some basic questions. It would be great if you could bring lights on it (thanks in advance :smiling_face_with_smiling_eyes: )

I know it will take some time to answer, but i think it will be helpfull for the next new developpers =)

1.DMA chapter:

• A peripheral must send a request to DMA to launch the data transfer:
  • For example: to launch ADC acquisition with DMA at a fix frequency, i must set a timer triggering an interruption at the fix frequency (TIM1_TRGO or TIM1_CC4 or TIM3_TRGO or TIM14_TRGO), which will launch an ADC acquisition followed by a request sent to DMA which will launch the transfer of the converted data to memory?
  • In more details:
    • DMA channel can be enable thanks to EN bit 0 ofr DMA_CCRx which activate the DMA channel
    • DMA_CSELR register is for DMA request mapping, for example: ADC on channel 1.

=> Which of the above condition trigger the DMA transfer ? As i understand the DMA channel Configuration sequence code exampe,

I guess DMA channel should be enable first and the DMA request mapping triggers the DMA. Is that correct ?

2.Interrupts and Events chapter:

• What's the difference between NVIC and EXTI (this is not clear for me):
  • EXTI is used for GPIO events/interruptions wheareas NVIC couldn't.
  • EXTI can be used to wake up the uC whereas NVIC couldn't
  • Both EXTI and EXTI can be used with internal peripherals
  • EXTI are parts of the NVIC ?
  • In which case should i use NVIC or EXTI ?
• What is the difference beween EVENT and interrupts? I see that for EVENT, there is no need to clear EXTI peripheral interrupt bit and the peripheral NVIC IRQ channel bit after a uC wake-up.
• Configuring the mask bit in the EXTI_IMR or EXTI_EMR register means to set the bit corresponding to the good GPIO. For example: i want an interruption trigrered by PB1. I should first put 0010 into EXTI1 bits of the SYSCFG_EXTICR1 register and set the bit #1 of the EXTI_IMR. Is that correct?
• What happens if i set up a rising AND failing trigger at the same time for that PB1 interruption example, both will be detected ?
• The EXTI_SWIER register let us the user to trigger an interrupt/event by itself instead of an automatic trigger by the peripheral. Is that correct ? This set the corresponding into the EXTI_PR register. What's the point of doing a not automatic triggered interruption/event ?
• What's the point to send a request to DMA by a Timer? what could be the data transfered from one to the other except the counting value ? I see for PWM, that it could send duty cycle or period with DMA but i still don't get the point

3.ADC chapter

• When we want the ADC to be triggered thanks a timer, the ADC should be configured for it and the ADCSTART bit must set manually as a prerequisite to let the ADC be triggered by the timer. Is that correct?
• I see that if DMA has reached the last DMA transfer, a DMA_EOT interrupt occurs . But I don't see such a bit called this way in the DMA chapter. Is it the TCIFx bit of DMA_ISR register ?
• Moreover, to let the ADC makes new request to DMA after a DMA_EOT interrupt, the CTCIFx bit of DMA_IFCR must be set. Is that correct ?
• I see on Single conversion sequence code example - Software trigger that the scan direction is made after the conversion itself. Is that a mistake that it is not done before the conversion?

4.For the Timers part, i am still studying..:anxious_face_with_sweat:

Thank you ,

[waclawek.jan]

> I guess DMA channel should be enable first and the DMA request mapping triggers the DMA. Is that correct ?

Yes. But ADC presents an extra complication, maybe as an initial experiment, you may want to do a timer-triggered transfer, maybe from memory to GPIO or other TIM.

Try using it to blink a LED without any software running in main loop, only initializing peripherals. I may have some examples in that direction on efton.sk.

Doing that exercise will maybe answer your "why".

> EXTI

NVIC is part of processor core handling all interrupts. EXTI only interface the pin-related interiors, plus some few others which are wakeup related. Both edges generate interrupt, if you are able to process them fast enough.

>DMA_EOT

I don't use Cube not any other "library" exactly because they do these unnecessary renames. Cube is open source so you can look these things up yourself.

> DMA_IFCR

That's a register to *clear* already set flags.

>studying..:anxious_face_with_sweat:

The key is to both read and experiment. After reading about some feature, write a simple test program to verify if you've understood correctly what you've just read.

JW