STM32 runın at 16 mhz

[FaintSmile]

Posted on December 14, 2013 at 09:32

I wrote 1 sn delay code for stm32 and ı used 168 mhz system clock.My delay cycle ıs 16000 for each ms and ıt work led blınk 1 sn.It dıdn't work when ıt was 168000 shouldn't it have worked at 168000 cycle.my code ıs

**

**  File        : main.c

**

**  Abstract    : main function.

**

**  Functions   : main

**

**  Environment : Atollic TrueSTUDIO(R)

**                STMicroelectronics STM32F4xx Standard Peripherals Library

**

**  Distribution: The file is distributed “as is,�? without any warranty

**                of any kind.

**

**  (c)Copyright Atollic AB.

**  You may use this file as-is or modify it according to the needs of your

**  project. This file may only be built (assembled or compiled and linked)

**  using the Atollic TrueSTUDIO(R) product. The use of this file together

**  with other tools than Atollic TrueSTUDIO(R) is not permitted.

**

*****************************************************************************

*/

/* Includes */

#include ''stm32f4xx.h''

/* Private macro */

/* Private variables */

/* Private function prototypes */

/* Private functions */

/**

**===========================================================================

**

**  Abstract: main program

**

**===========================================================================

*/

void delay_ms(int delay1)

{

delay1 = delay1*16000;

while (--delay1)

{

}

}

int main(void)

{

GPIO_InitTypeDef GPIO_InitStruct;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

GPIO_InitStruct.GPIO_Pin = GPIO_Pin_15 | GPIO_Pin_14 | GPIO_Pin_13 | GPIO_Pin_12; // we want to configure all LED GPIO pins

GPIO_InitStruct.GPIO_Mode = GPIO_Mode_OUT; // we want the pins to be an output

GPIO_InitStruct.GPIO_Speed = GPIO_Speed_100MHz; // this sets the GPIO modules clock speed

GPIO_InitStruct.GPIO_OType = GPIO_OType_PP; // this sets the pin type to push / pull (as opposed to open drain)

GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL; // this sets the pullup / pulldown resistors to be inactive

GPIO_Init(GPIOD, &GPIO_InitStruct);  // this passes the configuration to the Init function which takes care of the low level stuff

  /* Infinite loop */

  while (1)

  {

// if(1 == GPIO_ReadInputDataBit( GPIOA,GPIO_Pin_0))

// {

// while(1 == GPIO_ReadInputDataBit( GPIOA,GPIO_Pin_0));

 GPIO_SetBits ( GPIOD, GPIO_Pin_14) ;

 delay_ms(1000);

 GPIO_ResetBits (GPIOD, GPIO_Pin_14) ;

 delay_ms(1000);

// }

  }

}

/*

 * Callback used by stm32f4_discovery_audio_codec.c.

 * Refer to stm32f4_discovery_audio_codec.h for more info.

 */

void EVAL_AUDIO_TransferComplete_CallBack(uint32_t pBuffer, uint32_t Size){

  /* TODO, implement your code here */

  return;

}

/*

 * Callback used by stm324xg_eval_audio_codec.c.

 * Refer to stm324xg_eval_audio_codec.h for more info.

 */

uint16_t EVAL_AUDIO_GetSampleCallBack(void){

  /* TODO, implement your code here */

  return -1;

}

[Tesla DeLorean]

Posted on December 14, 2013 at 13:16

If you are concerned about the processor speed, use the MCOx pins and output internal clocks, and measure them on a scope.

Observe that the processor in fact starts for a 16 MHz HSI clock, and has to be switched to something else, typically via SystemInit() in system_stm32f4xx.c

Finally look at the assembler code generated by the compiler, and the optimization level selected. Unless you're writing code in assembler you probably have little control of cycle level performance.

[FaintSmile]

Posted on December 15, 2013 at 09:11

Clive you are right but why ıs ıt happening for  exapmle when ı use systemclick for delays lle these 

 if (SysTick_Config(168000000 / 1000))

 {

   /* Capture error */

   while (1);

 }

Delay(1000);

it does really waits for 1 second but when ı use my 1 second delay code lke these

void delay_s

 

(int delay2)

{

delay2 = delay2*168

0

0

0;

while (delay2--)

{

}

}

Delay(1000);

it waits more than 10 second ı dıdn't understant why it waits more.ısn't ıt te same thing its like my main fuction has a diffrent clock speed from systemclock and it is like 8mhz or smtn like that

[Tesla DeLorean]

Posted on December 15, 2013 at 15:00

The processor doesn't natively run C code, so assuming it's going to take a single cycle per loop iteration probably isn't going to hold water. To understand where the 10 cycles go you'll want to review the code output by the compiler.

[Andrew Neil]

Posted on December 16, 2013 at 01:16

''The processor doesn't natively run C code, so assuming it's going to take a single cycle per loop iteration probably (sic?) isn't going to hold water''

I'd say it is certainly  not going to hold water!

In fact, any assumption - unless fully  qualified by compiler, version, and complete settings - about a direct correspondence from 'C' source lines to machine code is unlikely to hold water.

http://www.8052.com/forum/read/162556