Delay function with TIM14 in nucleo G031K8

[Tommino]

void TIM14_init(void){
	RCC->APBENR2|=(1<<15);
	TIM14->PSC= 31;
	TIM14->SR=0;
	TIM14->CNT=0;
	TIM14->EGR|=(1<<0);
}
void TIM14_delay_us (int delay_us){
	TIM14->ARR = delay_us;
	TIM14->CR1|= (1<<0); // counter enabled
	while (!((TIM14->SR)&1)); // wait Update flag to be set
}

Hi,

I have written these two functions to init TIM14 and perform a us delay. It seems to not work. Can you help me?

[Antoine Odonne]

Dear Tomino,

The fact the SR LSB is already set is surprising in this setup indeed, but I don't see something incorrect. Did you tried to clear it within the delay_us function ?

Thank you and regards,

Antoine

[waclawek.jan]

> It seems to not work.

 How do you know?

JW

[Tommino]

Hi @Community member​ 

Sorry if I was not complete but I thought that the mistake was in myTIM14 functions.

I discovered that they works correctly but only if TIM14_delay_us is put after this function  MX_GPIO_Init(); that MX produces automatically (I am not using any HAL functions but only creating the project automatically in STM32 cube ide selecting the nucleo board that I am using and  MX_GPIO_Init(); comes out)

TIM14_delay_us works fine if it is used in the while(1) loop after all the init functions.

TIM14_delay_us does not work if it is used before MX_GPIO_Init();

I did not figure out why it is happening so far

[waclawek.jan]

> TIM14_delay_us does not work

I still don't know what do you mean by "does not work" here.

JW

[Tommino]

Sorry @Community member​ 

Does not work means that the function does not produce the delay (I can see it because I blink a led). I will try to give you some more details

Forget what I wrote before. My function TIM14_delay_us produces the delay in the led blinking only if write it twice.

example:

TIM14_delay(10000);

TIM14_delay(10000);

produces a 10 ms delay.

I will try to describe what happens

If I call the function only one time, in the TIM14 register I can see the UIF flag immediately raised (eventhough I write TIM14->SR=0;). I can see it in live expression

[waclawek.jan]

> TIM14->EGR|=(1<<0);

This sets the Update flag so clear SR before you start the counter in delay.

Also stop the counter after delay.

JW​

[Tommino]

Hi @Community member​ ,

I still have the same issue. The delay is produced only if I call TIM14_delay twice. Do you have any other suggestion?

Below there is the updated code.

void TIM14_init_delay(void){
	RCC->APBENR2|=(1<<15);
	TIM14->PSC= 16000-1; // 16 MHz clock --> 1000 Hz timer clock
	}
 
void TIM14_delay (int delay_ms){
	TIM14->SR=0;
	TIM14->CNT=0;
	TIM14->ARR = delay_ms;
	TIM14->CR1|= (1<<0); // counter enabled
	while (!((TIM14->SR)&TIM_SR_UIF)); // wait Update flag to be set
	TIM14->CR1&= ~(1<<0);
}

[waclawek.jan]

At this point I have no more ideas.

JW

[waclawek.jan]

Isn't it that only the very first delay after reset "does not work" (finishes much faster than all subsequent calls of the function)? If yes, that's because you *do* need the forced update (by setting EGR.UG) after setting PSC, as PSC is unconditionally preloaded. In other words, the very first run of that function works with the default PSC=0, and only after the Update happens at the end of that first run, PSC gets loaded and subsequent calls use it.

JW