STM32H743I-EVAL running off frequency

Posted on March 03, 2018 at 03:40

The consequences of not initializing local/auto variables properly...

Original code:

static void SystemClock_Config(void)

{

RCC_ClkInitTypeDef RCC_ClkInitStruct;

RCC_OscInitTypeDef RCC_OscInitStruct;

HAL_StatusTypeDef ret = HAL_OK;

/*

CORE=401060800, 401.06 MHz

CPUID 411FC271 DEVID 450 REVID 1001

Cortex M7 r1p1

C0000038 200017C0 00000000

10110221 12000011 00000040

FPU-D Single-precision and Double-precision

HCLK=200530400, 200.53 MHz

APB1=100265200, 100.27 MHz

APB2=100265200, 100.27 MHz

PLL1_Q_CK=200530400, 200.53 MHz

PLL2_R_CK=0, 0.00 MHz

480 x 272

*/

...

}

Modified code:

static void SystemClock_Config(void)

{

RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

RCC_OscInitTypeDef RCC_OscInitStruct = {0};

HAL_StatusTypeDef ret = HAL_OK;

/*

CORE=400000000, 400.00 MHz

CPUID 411FC271 DEVID 450 REVID 1001

Cortex M7 r1p1

STM32H7xx

C0000038 200017C0 00000000

10110221 12000011 00000040

FPU-D Single-precision and Double-precision

HCLK=200000000, 200.00 MHz

APB1=100000000, 100.00 MHz

APB2=100000000, 100.00 MHz

PLL1_Q_CK=200000000, 200.00 MHz

PLL2_R_CK=0, 0.00 MHz

480 x 272

*/

...

}

The USART can recover from this, TIM might be marginally off frequency. Also has the potential to be unpredictable.

Here from 

STM32Cube_FW_H7_V1.2.0\Projects\STM32H743I_EVAL\Applications\Display\LTDC_PicturesFromSDCard\Src\main.c

but systemic in the examples.