Skip to main content

STM32F4 Discovery: Clock frequency

So you have got an STM32F4 discovery board in your hands. I can surely assume one of the reason you got this nifty little development board is it's computing capability at 168MHz.
However if you are not cautious, you may not achieve the maximum clock speed the device could achieve.If u are not careful (sometimes it happens) the controller would run at lower clock.Obviously that is not a bad thing in power critical applications.Here are some steps to ensure the system is running at its peak performance

STEP 1:

Download clock configuration tool from ST, file named AN3988
http://www.st.com/internet/mcu/product/252149.jsp

STEP 2:

Open the clock configuration tool using excel and change HCLK to 168 MHz.You can select on other options and PLL frequencies also (Know what you are doing else leave it as it is).Click generate.If values are OK then no errors would be shown.Then click on generate.Then close the excel file.You should have got a system_stm32f4xx.c file in the folder.Use it in your project.

STEP 3:

In stm32f4xx.h file ensure HSE (external clock) value is 8 MHz



STEP 4:
In startup_stm32f4xx.c file change comment on SystemInit() function



to


STEP 5:
On the same file down under there will be a function Default_Reset_Handler(void)after assembly code towards the end add a line of code calling SystemInit() BEFORE calling main()
ie, change to

SystemInit();
main();

That`s it!
now in main function we can add 

RCC_HSEConfig(RCC_HSE_ON);
while(!RCC_WaitForHSEStartUp())
{
}

this ensures HSE is enabled and will wait for clock to be stabilized.
Hope this helps

Comments

  1. SIR,
    I HAVE A STM32F4-DISCOVERY BOARD & I WANT TO PASS LOOK-UP TABLE ( STORED IN FLASH ) THROUGH ANY ONE GPOI PORT OF IT...(THE DATAS ARE ALL 16 BIT)
    & I NEED EACH 16 BIT DATA IN ONE INSTRUCTION TO OUT AT PORT PIN (i.e. NOT AS 2 SUCCESSIVE 8 BIT DATA BY 2 CONSECUTIVE CYCLE OF CLK OR LIKE )IT MAY BE 32 BIT DATA .WITH PADDED ZEROS ...U CAN OFFER ANY CLK SPEED ...grateful to you..for your previous post also... helped me a lot for my final year project... I like to have a chat with u at your will

    ReplyDelete
  2. sending 16bit data can be easily done by writing the ODR register of the port in an instruction say, GPIOA-> ODR &= (16-bit data).Glad that the posts was something useful for you! regards

    ReplyDelete
  3. what do we do if the excel tool won't work in Excel 2010 ?
    pccmd@comcast.net

    ReplyDelete
  4. It should be compatible i used office 2010 to view it.never had any problem.try reinstalling it

    ReplyDelete
  5. This comment has been removed by the author.

    ReplyDelete
  6. Hi Thank you for this article.

    I am trying to use HSI and PLL. I am NOT using the Excel tool.
    I am not sure if I'm doing it right. PLL ready flag is not set.

    I have included the following code in my main.c


    //------ To Select PLL source clock ---------------
    RCC->PLLCFGR &= ~RCC_PLLCFGR_PLLSRC; // Enable HSI for PLL source

    //*************To set PLL out put as 152MHz***********************

    // VCO ip clock freq (VCO ip/PLLM) => HSI/16 => 1Mhz
    // PLLM = 16
    RCC->PLLCFGR &= ~RCC_PLLCFGR_PLLM;
    RCC->PLLCFGR |= RCC_PLLCFGR_PLLM_4;

    // VCO op => VCO ip x PLLN => 1 * 304 => 304MHz
    // PLLN = 304 => B100110000
    RCC->PLLCFGR &= ~RCC_PLLCFGR_PLLN;
    RCC->PLLCFGR |= RCC_PLLCFGR_PLLN_4;
    RCC->PLLCFGR |= RCC_PLLCFGR_PLLN_5;
    RCC->PLLCFGR |= RCC_PLLCFGR_PLLN_8;

    // PLL op => VCO op/PLLP => 304/2 => 152Mhz
    // PLLP = 2
    RCC->PLLCFGR &= RCC_PLLCFGR_PLLP;

    //--- Turn ON PLL
    RCC->CR |= RCC_CR_PLLON;

    //---- Wait for PLL lock
    while( !(RCC->CR & RCC_CR_PLLRDY) ); // GET STUCK HERE


    //------ SET PLL output as SYS clock -------
    RCC->CFGR &= 0xfffffffe;
    RCC->CFGR |= RCC_CFGR_SW_PLL;



    I am ok running Sys Clock directly by HSI at 16Mhz


    Thank you
    John

    ReplyDelete
  7. configuration de clock de microcontroleur
    par exemple : fréquence1= 30 méga ,80 méga, 120 méga, Max
    --------------------------------------------------------------------------------------
    un volantaire pour travail ce projet SVP

    ReplyDelete

Post a Comment

Popular posts from this blog

Arduino as USB to Serial converter

Electronics prototyping was taken to new heights by the introduction of arduino. The small board could do many wonderful things,but the beauty that makes it stand apart from others is it`s versatility and easiness. Most of us while doing our projects would have searched for a communication method with PC, and ended up using USART by level converters (MAX232) or perhaps a USB-Serial cable.Serial ports are disappearing from systems these days. Obviously USB is the only choice..So what to do? First thing you would say is to use a USB to serial converter cable that is cheap to buy. Unfortunately as many of you would have observed these are not  reliable many a times. next option is to use a FTDI breakout boards like this https://www.sparkfun.com/products/9115 . So if you can`t reach out for an FTDI board or any of those serial converter cables, you`l think you are doomed just like i did at that time.So no way out? Nope there is a way! Do you have an arduino sitting around

STM32F4 Discovery : GPIO

The most basic thing one would do with an MCU would be how to control the IO pins right? So how do we program the GPIO pins on STM32F4Discovery board? Let's take a look at it now, First and foremost we need to add stm32f4xx_gpio.h and stm32f4xx_rcc.h header files to be included in the project. Once that is done we must enable clock to the port (whichever port you would like to use) Each peripheral bus is detailed in the datasheet and we can use this information to enable system clock programmatically based on our application. Then we have to set parameters for configuring GPIO pins The various options are self explanatory.You can adjust the settings based on your application. Now lets try to toggle pin14 from PORTD which is an onboard LED on our discovery board. We've done it! Now you can compile it and see the onboard LED blinking ON and OFF! So the final code looks something like