STM32 Timers + Interruptions - Error

[ee06091]

Posted on August 28, 2013 at 12:46

Hi,

I set an interruption handler for a timer. Each time it calls the handler I change the state of a IO. But I'm getting problems for frequency above 80kHz. If I set the period to:

TIM_TimeBaseStructure.

TIM_Period

= SystemCoreClock/

160000

-

1

; I got an 80kHz in the channel output and in the IO that is changed by the interruption: Channel-0: PA2 - Timer 2 Chanel 2 Channel-1: PC9 - IO But if I set the period to:

TIM_TimeBaseStructure.

TIM_Period

= SystemCoreClock/

160000

-

1

;

It will create a 85kHz on OC2 but the IO drive by the interruption can't handle it. Am I in the limit of normal io speed? The measured frequency for the IO is 42kHz.

The code:

#include <stm32f10x.h>

#include <stm32f10x_rcc.h>

#include <stm32f10x_gpio.h>

#include <stm32f10x_tim.h>

#include <misc.h>


#define STPDRV_TIMFREQ 100000


static
__IO uint8_t ledval;

static
__IO uint8_t change;


int
main(
void
)

{

ledval=0;

change=0;


GPIO_InitTypeDef GPIO_InitStructure;

TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;

TIM_OCInitTypeDef TIM_OCInitStructure;


//Configure Clocks

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM2, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);


//Configure GPIO PC9

GPIO_StructInit(&GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;

GPIO_Init(GPIOC, &GPIO_InitStructure);


//Configure GPIO PA1

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_Init(GPIOA, &GPIO_InitStructure);


//configure NVIC

NVIC_InitTypeDef NVIC_InitStructure;


NVIC_InitStructure.NVIC_IRQChannel = TIM2_IRQn;

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);


//configure timer

TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);

TIM_TimeBaseStructure.TIM_Prescaler = 0;

TIM_TimeBaseStructure.TIM_Period = SystemCoreClock/170000 - 1;

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;

TIM_TimeBaseInit(TIM2, &TIM_TimeBaseStructure);


//configure channel TIM2 C2

TIM_OCStructInit(&TIM_OCInitStructure);

TIM_OCInitStructure.TIM_OCMode = TIM_OCMode_Toggle;

TIM_OCInitStructure.TIM_OutputState = TIM_OutputState_Enable;

TIM_OC2Init(TIM2, &TIM_OCInitStructure);


/* TIM2 TRGO selection */

TIM_ITConfig(TIM2, TIM_IT_Update, ENABLE);

TIM_Cmd(TIM2, ENABLE);


while
(1){

if
(change){

GPIO_WriteBit(GPIOC, GPIO_Pin_9, (ledval)? Bit_SET : Bit_RESET);

ledval = 1 - ledval;

change=0;

}


};


return
0;

}


void
TIM2_IRQHandler(
void
){


change=1;


TIM_ClearITPendingBit(TIM2,TIM_IT_Update);

}



#ifdef USE_FULL_ASSERT

void
assert_failed(uint8_t* file, uint32_t line)

{

while
(1);

}

#endif

Thanks for your help :) #stm32 #timer #interrupt #exti

[Tesla DeLorean]

Posted on August 28, 2013 at 13:38

Interrupting the processor at several hundred KHz, is probably getting close to saturating a 24 MHz processor. Limited by the number of instructions per interrupt.

You'd definitely want to change your interrupt so it doesn't re-enter (M3/NVIC pipeline hazard), by doing the clearing early.

void TIM2_IRQHandler(void)
{
TIM_ClearITPendingBit(TIM2,TIM_IT_Update);
change=1;
}