full speed micro

[ezrab]

Posted on October 05, 2010 at 09:39

what is the full speed system clock i can

achieve with stm32-discovery?

and how?

now i work with 8Mhz cristal.

[Tesla DeLorean]

Posted on October 05, 2010 at 16:35

It is documented to be 24 MHz, you need to configure the PLL, and you can use the AHB/APB1/APB2 with no scaling (ie at 24 MHz). The flash will also run at this speed without wait states.

The PLL would be set to (HSE / 2) * 6

If you are using the standard library you can select the speed in system_stm32f10x.c by changing a #define, or program it yourself, either way review the code in the ST firmware library (at the address printed on the board) to see how to configure the clocks.

[ezrab]

Posted on October 06, 2010 at 08:10

thanks for the replay .

i used this configuration:

 RCC->APB2ENR |=0x14;

 RCC->CR = (uint32_t)0x00000000;

 RCC->CFGR=0x4000005;

 RCC->CR=0x1090000;

but still i cant get any higher then 8Mhz.

why?

[joa]

Posted on October 06, 2010 at 10:18

As far as I can see from your magic numbers you don't select the PLL as system clock. You can try something like this (it seems to work but I don't know if it's the correct way to do it)

    //// Configure system clock PLL*3 driven by  external high speed

    //// oscillator (8 MHz crystall) 24MHz

    // Turn on high speed external oscillator

    RCC->CR |= RCC_CR_HSEON;

    // Wait until it's ready

    while ((RCC->CR & RCC_CR_HSERDY) == 0)

        ;

    // Select PREDIV1 as PLL source and sett PLL mul to 3 (set bit 0)

    // for 8*3 = 24 MHz

    RCC->CFGR |= RCC_CFGR_PLLSRC | RCC_CFGR_PLLMULL_0;

    // Start PLL

    RCC->CR |= RCC_CR_PLLON;

    // Wait until it's ready

    while ((RCC->CR & RCC_CR_PLLRDY) == 0)

        ;

    // Select PLL as system clock

    RCC->CFGR |= RCC_CFGR_SW_PLL;

    // Here we can check if PLL is used, and maybe disable HSI

    // Disable HSI

    RCC->CR &= ~RCC_CR_HSION;

(Is there some kind of code tags one can use?)

[ezrab]

Posted on October 06, 2010 at 10:30

thank you very much it works :)