HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_SYSCLK, RCC_MCODIV_4);

/**
  * @brief  Select the clock source to output on MCO pin(PA8).
  * @note   PA8 should be configured in alternate function mode.
  * @param  RCC_MCOx  specifies the output direction for the clock source.
  *          For STM32L4xx family this parameter can have only one value:
  *            @arg @ref RCC_MCO1  Clock source to output on MCO1 pin(PA8).
  * @param  RCC_MCOSource  specifies the clock source to output.
  *          This parameter can be one of the following values:
  *            @arg @ref RCC_MCO1SOURCE_NOCLOCK  MCO output disabled, no clock on MCO
  *            @arg @ref RCC_MCO1SOURCE_SYSCLK  system  clock selected as MCO source
  *            @arg @ref RCC_MCO1SOURCE_MSI  MSI clock selected as MCO source
  *            @arg @ref RCC_MCO1SOURCE_HSI  HSI clock selected as MCO source
  *            @arg @ref RCC_MCO1SOURCE_HSE  HSE clock selected as MCO sourcee
  *            @arg @ref RCC_MCO1SOURCE_PLLCLK  main PLL clock selected as MCO source
  *            @arg @ref RCC_MCO1SOURCE_LSI  LSI clock selected as MCO source
  *            @arg @ref RCC_MCO1SOURCE_LSE  LSE clock selected as MCO source
  @if STM32L443xx
  *            @arg @ref RCC_MCO1SOURCE_HSI48  HSI48 clock selected as MCO source for devices with HSI48
  @endif
  * @param  RCC_MCODiv  specifies the MCO prescaler.
  *          This parameter can be one of the following values:
  *            @arg @ref RCC_MCODIV_1  no division applied to MCO clock
  *            @arg @ref RCC_MCODIV_2  division by 2 applied to MCO clock
  *            @arg @ref RCC_MCODIV_4  division by 4 applied to MCO clock
  *            @arg @ref RCC_MCODIV_8  division by 8 applied to MCO clock
  *            @arg @ref RCC_MCODIV_16  division by 16 applied to MCO clock
  * @retval None
  */
void HAL_RCC_MCOConfig( uint32_t RCC_MCOx, uint32_t RCC_MCOSource, uint32_t RCC_MCODiv);