How to Fix Error: 'RCC_PLLConfig' was not declared in this scope

Identify the Error Scope

• Ensure your include paths are set up correctly. The error ‘RCC\_PLLConfig’ was not declared in this scope usually indicates a missing or inaccessible declaration, commonly in header files.
• Verify that you have included all necessary headers. A typical header file for STM32 series would be #include "stm32f10x\_rcc.h" or something corresponding to your specific MCU series.
• Check the project settings to confirm that MCU-specific library paths are correct and the right microcontroller family is chosen.

Review Your Environment

• Ensure you are using a compatible IDE or build system like STM32CubeIDE, Keil, or Eclipse with ARM toolchain support. Misconfigured toolchains often lead to such errors.
• If using STM32CubeMX, regenerate the initialization code to ensure all peripheral setup and configuration files are included.
• Ensure you have the latest CMSIS version compatible with your MCU, as newer releases can deprecate or rename functions.

Check Function Existence

• Open the relevant header/source files (like stm32f10x_rcc.c/.h) to locate ‘RCC_PLLConfig’. It might be deprecated or renamed in newer HAL/LL libraries.
• If the function is not found, consult the STM32 MCU family reference manual or the ST Microelectronics webpage for alternative or updated functions.
• Review the latest STM32Cube MCU Package for your device to understand differences in peripheral setup between SPL (Standard Peripheral Library) and HAL/LL.

Adopt Alternative Approaches

• If ‘RCC_PLLConfig’ is deprecated, use the HAL library counterparts. A typical PLL configuration setup might replace direct register programming with function calls like HAL_RCC_OscConfig() and HAL_RCC\_ClockConfig().
• For instance, the pllConfig structure is used in HAL for configuring RCC rather than direct function calls. An example setup might look like this:

  RCC_OscInitTypeDef RCC_OscInitStruct = {0};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
  
  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.PLLMUL = RCC_PLL_MUL9;
  
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
  {
      // Handle Error
  }
  
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
  
  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_2) != HAL_OK)
  {
      // Handle Error
  }
  

Refactor and Simplify Code

• Evaluate any macro definitions or shortcut configurations to ensure they are referenced correctly. Sometimes, macros might obscure the actual function calls or cause misconfiguration.
• Simplify the initialization process by compartmentalizing the code into distinct configuration blocks for ease of debugging and clarity.