SystemClock_Config(void) unexpected behavior

[AirchipTeknoloji]

Desktop:

OS: macOS 14.3.1
Arduino IDE version: 2.3.1
STM32 core version: 2.7.1
Upload method: STM32 Cube Programmer (Serial)

Board:

Name: STM32F0 based

Board PART NUMBER:

Name: STM32F030C8TX

Description:

I have custom STM32F030C8T6 based board and when I use HSI or nothing change at sketch level everything works as expected.
But when I want to use HSE and use SystemClock_Config(void) at sketch level, the problem arises. Everything goes up to 2x faster. If I set usart to 9600 baud rate, I can read it correctly at 19200 baud rate. If I make a led on and off for 10 secs, It goes for 5 sec.

Here my very basic skech to reproduce error:

HardwareSerial Serial1(PB7, PB6);
extern "C" void SystemClock_Config(void);
extern "C" void SystemClock_Config(void) {
  RCC_OscInitTypeDef RCC_OscInitStruct = { 0 };
  RCC_ClkInitTypeDef RCC_ClkInitStruct = { 0 };

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  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_MUL3;
  RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;
  if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK) {
    Error_Handler();
  }

  /** Initializes the CPU, AHB and APB buses clocks
  */
  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_SYSCLK
                                | RCC_CLOCKTYPE_PCLK1;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_HSE;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1) != HAL_OK) {
    Error_Handler();
  }
}
// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  Serial1.begin(9600);
  pinMode(LED_BUILTIN, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  Serial1.println("HEY");  // turn the LED on (HIGH is the voltage level)
  delay(5000);                      // wait for a second
                    // wait for a second
}

I use 16mhz external btw.
Nothing changes when I change RCC_PLL_MUL3 to anything or RCC_PREDIV_DIV1 to anything. Using Arduino IDE 2.3.1 and latest version of (2.7.1) STM32 Based Boards. I tried so many things but can't make it work. Is this issue related to me or core related? Any help will be appreciated.

Thanks in advance.
Aykut.

[AirchipTeknoloji]

For anybody facing this issue:

It requires also to redefine the default HSE_VALUE using the build_opt.h:
-DHSE_VALUE=16000000U