STM32G431 bug #2727

Buldakov-A · 2025-05-18T14:04:55Z

Buldakov-A
May 18, 2025

I am configuring the stm32g431 chip to be powered by an external quartz oscillator to operate at 32 MHz.
The MCO pin must have a frequency of 16 MHz to check the correct operation of the generator settings.
Version 2 of the code works fine from an external oscillator and outputs a frequency of 16 MHz at the MCO output.
But if I remove an unused interrupt from the code, then everything stops working.
// SystemClock_Config();
//void SystemClock_Config(void)
//{}
After that, the chip starts operating from an internal generator at a frequency of 170 MHz and on the MCO pin we have a frequency equal to 85 MHz.
Version 1 of the code does not work.

STM32G431_ver1.txt
STM32G431_ver2.txt

Answered by fpistm

May 21, 2025

Well, I've tested a simple sketch with a Nucleo G431RG, set the HSE_VALUE to 24MHz, and configure the clock to use HSE and have a sysclock at 100MHz:

extern "C" void SystemClock_Config(void) {
  RCC_OscInitTypeDef RCC_OscInitStruct = {};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {};

  /** Configure the main internal regulator output voltage
  */
  HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1);

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI | RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSIState = R…

View full answer

fpistm · 2025-05-19T07:47:39Z

fpistm
May 19, 2025
Maintainer

Hi @Buldakov-A

But if I remove an unused interrupt from the code, then everything stops working.

SystemClock_Config is not an "unused interrupt from the code".
You redefine the default SystemClock_Config to nothing. This function is called very soon in the init of the board.
So instead of doing this, simply define the new clock config in the SystemClock_Config.
Add an extern "C" before to prevent any issue as ino is converted in cpp file.

extern "C" SystemClock_Config() {
}

Note that HSE value used to compute freq is:

#if !defined  (HSE_VALUE)
#define HSE_VALUE    (8000000UL)            /*!< Value of the External oscillator in Hz */
#endif /* HSE_VALUE */

So if your HSE is not 8MHz, you have to redefine it to the correct value.

2 replies

Buldakov-A May 19, 2025
Author

I fixed and made changes to the version 3 code. Everything works too.

STM32G431_ver3.txt

And one more question.
When I clock from an internal generator, the time parameters are calculated correctly.
For example:
the time of 1 second is micros()=1000000.
But if I start clocking from an external oscillator at 8 MHz,
the time of 1 second is micros()=333333.
The micros() and millis() functions are clocked exactly 3 times slower.
I think that the external quartz frequency is spelled out incorrectly in the settings file and counts incorrectly when booting micros().
Where can I find the setting of this frequency?

fpistm May 19, 2025
Maintainer

No need to call the SystemClock_Config in the setup as said it is called early.
Nothing to do for the micros it is properly computed if the HSE value is correct as stated above.

Buldakov-A · 2025-05-21T06:31:59Z

Buldakov-A
May 21, 2025
Author

This statement is incorrect.
I checked it out. I am using an external quartz oscillator at a frequency of 8 MHz. With the frequency meter,
I checked the frequency on the MCO pin. I have written a test program for this check.
1 - I set the clocking from the external oscillator to a frequency of 100 MHz.
2 - I start timer 2 at the expense of clock pulses.
3 - Every 1000000 microseconds, I display the LCD2004 microsecond value and the Timer counter value 2.
The value should be displayed on the screen:
MICROS = 1000000
TIMER2 = 100000000
But my display shows the value
MICROS = 1000000
TIMER2 = 299517000
This means that the value of micros() is calculated incorrectly.

STM32G431_ver4.txt

1 reply

fpistm May 21, 2025
Maintainer

Well, I've tested a simple sketch with a Nucleo G431RG, set the HSE_VALUE to 24MHz, and configure the clock to use HSE and have a sysclock at 100MHz:

extern "C" void SystemClock_Config(void) {
  RCC_OscInitTypeDef RCC_OscInitStruct = {};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {};

  /** Configure the main internal regulator output voltage
  */
  HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1);

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI | RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = RCC_PLLM_DIV3;
  RCC_OscInitStruct.PLL.PLLN = 25;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
  RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
  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_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK) {
    Error_Handler();
  }
}

void setup() {
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);  // turn the LED on (HIGH is the voltage level)
  uint32_t s = micros();            // wait for a second
  while ((micros() - s) <= 1000000)
    ;
  digitalWrite(LED_BUILTIN, LOW);  // turn the LED off by making the voltage LOW
  s = micros();                    // wait for a second
  while ((micros() - s) <= 1000000)
    ;
}

Looking with a logic analyzer it is very close to the target.

micros() simply relies on the systick which is linked to the system core clock config.
So if really wrong then all clocks where wrong.

Testing your code to setup the TIM2 I found that the PSC is simply not properly configured as the tim internal clock is 100MHz and PSC is configured to 0 so clock still 100MHz. in 1 second, TIM2 counter count 100 000 000 . So you have to set PSC to 99 to have a clock divided by 100 (PSC+1) equal to 1MHz then you will have a counter of 1000000 as expected.
I've tested and it works:

static uint32_t lastm = 0;

extern "C" void SystemClock_Config(void) {
  RCC_OscInitTypeDef RCC_OscInitStruct = {};
  RCC_ClkInitTypeDef RCC_ClkInitStruct = {};

  /** Configure the main internal regulator output voltage
  */
  HAL_PWREx_ControlVoltageScaling(PWR_REGULATOR_VOLTAGE_SCALE1);

  /** Initializes the RCC Oscillators according to the specified parameters
  * in the RCC_OscInitTypeDef structure.
  */
  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI | RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.HSIState = RCC_HSI_ON;
  RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLM = RCC_PLLM_DIV3;
  RCC_OscInitStruct.PLL.PLLN = 25;
  RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
  RCC_OscInitStruct.PLL.PLLQ = RCC_PLLQ_DIV2;
  RCC_OscInitStruct.PLL.PLLR = RCC_PLLR_DIV2;
  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_CLOCKTYPE_PCLK2;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

  if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_3) != HAL_OK) {
    Error_Handler();
  }
}

void setup() {
  Serial.begin(115200);
  __HAL_RCC_TIM2_CLK_ENABLE();  // Включение тактирования таймера TIM2
  //---Инициализация таймера TIM2----------------------------------------------------------------------//
  TIM2->CR1 = 0;             // Остановка таймера
  TIM2->CCMR1 = 0x00000000;  // Сброс настроек каналов
  TIM2->CCER = 0x00000000;   // Сброс управления выходами
  TIM2->PSC = 99;             // Установка предделителя = 1  (PSC = 0)
  TIM2->ARR = 0xFFFFFFFF;    // Максимальное значение счетчика
  TIM2->EGR |= TIM_EGR_UG;   // Обновление регистров
  TIM2->CR1 |= TIM_CR1_CEN;
}

void loop() {
  while (1) {
    uint32_t curm = micros();
    uint32_t curt = TIM2->CNT;
    uint32_t delta = curm - lastm;
    if (delta >= 1000000) {
      TIM2->EGR |= TIM_EGR_UG;
      Serial.printf("Micros = %u, TIM2 = %u -> diff = %i\n", delta, curt, delta-curt);
      Serial.flush();
      lastm = curm;

    }
  }
}

Result:

11:49:12.063 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:13.059 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:14.054 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:15.050 -> Micros = 1000000, TIM2 = 1000000 -> diff = 0
11:49:16.049 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:17.047 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:18.042 -> Micros = 1000000, TIM2 = 1000000 -> diff = 0
11:49:19.040 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:20.069 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:21.066 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:22.061 -> Micros = 1000000, TIM2 = 1000000 -> diff = 0
11:49:23.059 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:24.054 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:25.048 -> Micros = 1000000, TIM2 = 999999 -> diff = 1
11:49:26.045 -> Micros = 1000000, TIM2 = 999999 -> diff = 1

Answer selected by fpistm

Buldakov-A · 2025-05-22T06:08:57Z

Buldakov-A
May 22, 2025
Author

I am using the STM32G431CBU6 chip.
An 8 MHz external quartz is soldered on the board.
Since the system frequency is correct, the quartz 8 MHz is used correctly to set the system frequency.
But to set the Micros() function, instead of an 8 MHz variable, a 24 MHz variable is used.
Therefore, an additional frequency division by 3 is necessary.

The question was: How can I change the frequency of 24 MHz for Micros() to 8 MHz?.

I checked your code.
The code is working correctly. Micros() = 1000000.
But you are using a pre-divider by 3 in the row RCC_OscInitStruct.PLL.PLLM = RCC_PLLM_DIV3;
and therefore the system frequency is 33.333 MHz instead of 100 MHz.
I feed this system frequency to the MCO pin and can measure it very accurately.

STM32G431_ver5.txt

2 replies

fpistm May 22, 2025
Maintainer

I already answered this. Default HSE_VALUE is 8MHz. I've define it to 24MHz for the nucleo as the HSE is 24MHz. I've simply reproduce your setup to have a sysclok at 100MHz.

fpistm May 22, 2025
Maintainer

The question was: How can I change the frequency of 24 MHz for Micros() to 8 MHz?.

No need to change as the default HSE_VALUE is 8MHz. micros works as expected you simply do not properly configure the timer. Simply set the PSC to 99 then your code will work.

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STM32G431 bug #2727

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