(SOLVED) Gap in performance between HSI & HSE ( Internal /External Clock )

[Lagodolio]

Hi,

I have a Nucleo STM32F767ZI with a X-Nucleo-PLC01A1 and a test application that cyclically switches ON/OFF the outputs .

All works fine when I use HSI, with Output LEDs that stay solid during ON state.

If I use High Speed Clock (in Cube MX, PCC->HSE->Crystal/Ceramic Resonator), LEDs blink with high freq, as a sort of refresh.

As you can see , I set both HSE & HSI to 16MHz, so working frequency are the same.

Can you help me or give me any suggestions?

This is HSI Clock:

while this is HSE:

Thanks and best regards,

Mario

[AvaTar]

This is what Cube supposedly wants to do.

Have you checked what actually happens, like the pulse frequency on the ouputs, or the system clock frequency ?

[Lagodolio]

The system appears as it is "slowed down", a "5s. delay" takes approx 10-11s.

It seems as a sort of prescaler was applied, but I'm no able to find where...

Code for HSE is:

void SystemClock_Config(void)
{
  RCC_OscInitTypeDef RCC_OscInitStruct;
  RCC_ClkInitTypeDef RCC_ClkInitStruct;
    /**Configure the main internal regulator output voltage */
 
  __HAL_RCC_PWR_CLK_ENABLE();
  __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
 
    /**Initializes the CPU, AHB and APB busses clocks */
 
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = 8;
  RCC_OscInitStruct.PLL.PLLN = 216;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
 
    /**Activate the Over-Drive mode*/
 
  if (HAL_PWREx_EnableOverDrive() != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
 
    /**Initializes the CPU, AHB and APB busses clocks */
 
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                              |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;
 
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_7) != HAL_OK)
  {
    _Error_Handler(__FILE__, __LINE__);
  }
 
    /**Configure the Systick interrupt time */
 
  HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
 
    /**Configure the Systick */
 
  HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
 
  /* SysTick_IRQn interrupt configuration */
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
 

That is virtually the same for HSI (with HSE substitute by HSI).

[Piranha · Accepted solution]

By default that board is fed with 8 MHz external clock from ST-Link. If You haven't modified the board, then the correct code is:

RCC_OscInitStruct.HSEState = RCC_HSE_BYPASS;
RCC_OscInitStruct.PLL.PLLM = 4;

[Lagodolio]

Thanks!! It works!!

So, setting F7 HSE clock @16MHz caused a sort of erroneus clock syncronism, infact system took double time to execute code!