MB Bugg

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8 years, 8 months ago.

CPU clock of "upto" 100MHz ???

From the datasheet it seems that these boards as sold only run at 8MHz !

The "high speed" clock input is taken from X1 on the STLINK section of the board. There is the option of low speed clock X2 at 32kHz or buying, installing and configuring your own X3

Maybe the thinking is that this is aimed Ardiuino lovers and we don't want to give them whip-lash injuries by giving them a 100MHz board to play with.

But it seems rather desceptive marketing constantly refering to this "upto" 100Mhz but never mentioning the REAL clock speed of the product being sold.

Is this OSC freq really the CPU speed or is mulitplied up internally? If so what is the true CPU clock of this board as sold?

Thanks.

Question relating to:

Last updated: 20 Apr 2021
Affordable and flexible platform to ease prototyping using a STM32F411RET6 microcontroller.

1 Answer

Wim Huiskamp
8 years, 8 months ago.

ARM processors have extented clock source selection, PLL multipliers and peripheral clockspeed dividers on board. There is no 'as sold' clockspeed. It all depends on software settings. The mbed lib will typically initialise the processor to the clockspeed mentioned on the mbed platform page.

Many thanks for the clarification.

So NUCLEO-F411RE will run at 100MHz when using mbed initialisations.

posted by MB Bugg 01 Aug 2015

Yes, it should run at 100MHz. You can always check the current clockfreq by using this code:

pc.printf("CPU SystemCoreClock is %d Hz\r\n", SystemCoreClock);
posted by Wim Huiskamp 02 Aug 2015