How to measure speed of STM32F429

[danielturcanu]

Posted on December 10, 2013 at 06:34

I have a STM32429I-EVAL board, initialized it and made it work, but I am not sure if the processor speed is up to max. The function RCC_GetClocksFreq returns 180 MHz, but cannot trust its return.

I did a loop to toggle LED1 and the max speed of toggle is 4 MHz.

while(1)

{

  STM_EVAL_LEDToggle(LED1);

}

This 4 MHz seems too low to me, I don't think the processor spends 45 cycles to toggle the led.

Is there a more precise way to measure the speed?

[Tesla DeLorean]

Posted on December 10, 2013 at 06:56

Use a TIMx_CHx pin of known ratio, or one of the MCOx pins?

[francescatodiego]

Posted on December 10, 2013 at 09:48

RCC_GetClocksFreq header note:

 * @note   The system frequency computed by this function is not the real

  *         frequency in the chip. It is calculated based on the predefined

  *         constant and the selected clock source:

You must define the correct HSE_VALUE (if external clock is used)

Add the compiler symblo define

HSE_VALUE=*clockvalue*

Example for 8MHz clock

HSE_VALUE= (8000000)

Check also PLL_M and PLL_N constants in system_stm32f4xx.c file

Default value for PLL_M and PLL_Nobtain max HCLK frrequency but with HSE_VALUE = 25MHz

You must change PLL_M and PLL_N values to obtain correct PLL frequency (must be between 190...400MHz)

HCLK is PLL freq/PLL_P value PLL_P minimum value 2 --> HCLK max value is half of PLL frequency