Unclear how to setup STM32L4+ clocks for SD card and LPUART

[magene]

I'm slowly learning how to use the STM32 family starting with the STM32L4R9-Discovery board. I use mostly VisualGDB and have run and modified a variety of UART examples and FATFs/uSD card examples. When I try to put them together so I can log data on the uSD card from sensors connected to a UART I seem to be running into errors where the examples I've used for just writing to the uSD card setup the clock one way but that configuration doesn't work for the UART.

My basic question is what reference can I go to to figure out how to setup the clocks properly for an app that uses both a UART and FATFs/uSD functionality? And more generally for any combination of peripherals?

I've also tried to use STM32CubeIDE and CubeMX to better understand how to configure the clocks but with less success.

More specifically, here's the SystemClockConfig subroutine from my working uSD example followed by the SystemClock_Config subroutine from my working UART example. They seem to be identical through line 27 then the uSD version does some more stuff but I don't see how that would break the UART. Any suggestions about what is wrong here would be greatly appreciated.

void SystemClock_Config(void)
{
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
 
  /* Enable voltage range 1 boost mode for frequency above 80 Mhz */
  __HAL_RCC_PWR_CLK_ENABLE();
  HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1_BOOST);
  __HAL_RCC_PWR_CLK_DISABLE();
 
  /* Enable MSI Oscillator and activate PLL with MSI as source */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
  RCC_OscInitStruct.MSIState = RCC_MSI_ON;
  RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
  RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
  RCC_OscInitStruct.PLL.PLLM = 1;
  RCC_OscInitStruct.PLL.PLLN = 60;
  RCC_OscInitStruct.PLL.PLLR = 2;
  RCC_OscInitStruct.PLL.PLLQ = 2;
  RCC_OscInitStruct.PLL.PLLP = 7;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
    /* Initialization Error */
    while(1);
  }
 
  /* To avoid undershoot due to maximum frequency, select PLL as system clock source */
  /* with AHB prescaler divider 2 as first step */
  RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV2;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;
  if(HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK)
  {
    /* Initialization Error */
    while(1);
  }
 
  /* AHB prescaler divider at 1 as second step */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  if(HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
  {
    /* Initialization Error */
    while(1);
  }
}

And here's the SystemClockConfig subroutine from the working UART app.

void SystemClock_Config(void)
{
	RCC_ClkInitTypeDef RCC_ClkInitStruct = { 0 };
	RCC_OscInitTypeDef RCC_OscInitStruct = { 0 };
  
	/* Enable voltage range 1 boost mode for frequency above 80 Mhz */
	__HAL_RCC_PWR_CLK_ENABLE();
	HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1_BOOST);
	__HAL_RCC_PWR_CLK_DISABLE();
 
	/* Enable MSI Oscillator and activate PLL with MSI as source */
	RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_MSI;
	RCC_OscInitStruct.MSIState = RCC_MSI_ON;
	RCC_OscInitStruct.MSICalibrationValue = RCC_MSICALIBRATION_DEFAULT;
	RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
	RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_MSI;
	RCC_OscInitStruct.MSIClockRange = RCC_MSIRANGE_6;
	RCC_OscInitStruct.PLL.PLLM = 1;
	RCC_OscInitStruct.PLL.PLLN = 60;
	RCC_OscInitStruct.PLL.PLLR = 2;
	RCC_OscInitStruct.PLL.PLLQ = 2;
	RCC_OscInitStruct.PLL.PLLP = 7;
	if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
	{
		/* Initialization Error */
		cout << "Error in SystemClock_Config" << endl;
		while (1) ;
	}
}

[Tesla DeLorean]

>>My basic question is what reference can I go to to figure out how to setup the clocks properly for an app that uses both a UART and FATFs/uSD functionality? And more generally for any combination of peripherals?

The reference manual should be pretty definitive.

UARTs will usually clock off the APB they are connected too.

The SD wire clock typically coming from the HCLK/SYSCLK for the CPU, or a "48 MHz" source from one or more PLL source.