Input capture problem

[LLah.1]

Hi all!

I'm trying to measure a PWM frequency signal using the input capture channel 1 of TIM3, but it won't work.

i'm using NUCLEO F446RE board, here is my code:

#include "stm32f4xx.h" // Device header

#include "lcd_H.h"

int main(void)

{

uint16_t capt1 = 0, capt2 = 0;

uint8_t lock = 1;

float Freq = 0.00;

//Clock Setup

RCC ->CR |= 1 << 18; //Enable bypass HSE

RCC ->CR |= 1 << 16; //Enable HSE

while(!(RCC ->CR & (1 << 17))); //wait HSE is ready

RCC ->CFGR &= ~(1 << 1); //HSE is used as system clock

RCC ->CFGR |= 1 << 0;

/**************************************************************************************/

//Configure PA6 as Input Capture channel 1

RCC ->AHB1ENR |= 1 << 0; //Enable clock for GPIOA

GPIOA ->MODER &= ~(1 << 12); //PA6 is used as Alternate function Mode: 10

GPIOA ->MODER |= (1 << 13);

GPIOA ->PUPDR &= ~(1 << 12); //Pull Down in PA6 : 10

GPIOA ->PUPDR |= (1 << 13);

GPIOA ->AFR[0] |= 1 << 24; //PA6 is Alternate function 1: 0001

/**************************************************************************************/

//Configure TIM3

LcdInit();

RCC ->APB1ENR |= 1 << 1; //Enable clock for TIM3

TIM3 ->ARR = 0xFFFF;

TIM3 ->PSC = 0;

TIM3 ->CR1 |= 1 << 0; //Enable counter

TIM3 ->CCMR1 = 0x01; //01: CC1 channel is configured as input, IC1 is mapped on TI1

//IC1F: 0000 No filter, sampling is done at fDTS

//IC1PSC: Input capture 1 prescaler: 00 no prescaler, capture is done each time an edge is detected on the capture input

TIM3 ->CCER |= (1 << 0); //1: Capture enabled

//positive edge

/**************************************************************************************/

while(1)

{

TIM3 ->SR &= ~(1 << 1); //CLEAR Flag

while(!(TIM3 ->SR & (1 << 1))); //Wait a capture occurs

if(lock){

capt1 = TIM3 ->CCR1;

lock = 0;

}

else{

capt2 = TIM3 ->CCR1;

if(capt2 > capt1)

{

Freq = capt2 - capt1;

}

else{

Freq = ((0xffff-capt1)+capt2) +1;

}

Freq = (float)8000000.00/Freq;

//Print value in the LCD

LcdSendData(0x01, COMMAND_MODE); //Clear LCD

LcdSetCursor(1, 1);

LcdSendString("F=");

LcdPrintfloat(Freq);

LcdSendString("Hz");

lock = 1;

}

}

}

In debugging the code stuck here while(!(TIM3 ->SR & (1 << 1))); please any help?

Thank you.

[TDK]

Enable CC1IE in DIER.

TIMx->DIER |= TIM_DIER_CC1IE

[LLah.1]

It doesn't work! And i don't want to use interrupt.

[berendi · Accepted solution]

Read back the registers, all of them. Do they contain what you expect?

There should be a few cycles delay after enabling peripheral clocks in RCC (see Delay after an RCC peripheral clock enabling in the errata). I'd just change the order of initialization

RCC ->AHB1ENR |= RCC_AHB1ENR_GPIOAEN; //Enable clock for GPIOA
RCC ->APB1ENR |= RCC_APB1ENR_TIM3EN; //Enable clock for TIM3, provides the required delay
//Configure GPIO
//Configure TIM3

Enable the counter i.e. TIM_CR1_CEN as the last thing after all other timer registers are set up.

Check PA6 - TIM3 mapping in the Alternate function table of the datasheet.

[waclawek.jan]

> GPIOA ->AFR[0] |= 1 << 24; //PA6 is Alternate function 1: 0001

Exactly as berendi said above:

JW

[LLah.1]

Thank you guys for the help, now it's working very well!