STM32WB HSE校准

通过改变RCC_HSECR寄存器中的HSETUNE[5:0]位域的值来校准HSE的输出频率

1、将HSE时钟配置为MCO模式输出到PA8引脚

HAL_RCC_MCOConfig(RCC_MCO1, RCC_MCO1SOURCE_HSE, RCC_MCODIV_1);

2、改变RCC_HSECR寄存器中的HSETUNE[5:0]位域的值（0-63）

LOOP((0<=p_otp->hse_tuning<=63):

__HAL_RCC_HSE_CONFIG(RCC_HSE_OFF);

 while (LL_RCC_HSE_IsReady())；

LL_RCC_HSE_SetCapacitorTuning(p_otp->hse_tuning);

__HAL_RCC_HSE_CONFIG(RCC_HSE_ON);

 while (LL_RCC_HSE_IsReady())；

通过不断改变p_otp->hse_tuning的值调整HSE的时钟频率直到PA8引脚上的时钟信号满足要求

3、保存HSETUNE[5:0]位域的值，将校准后的值保存在OTP区

#ifdef __GNUC__
typedef struct __attribute__((packed))
#else
typedef __packed struct
#endif
{
  uint8_t additional_data[6]; /*!< 48 bits of data to fill OTP slot (e.g: BD or MAC address, key..) */
  uint8_t hse_tuning;         /*!< Load capacitance to be applied on HSE pad */
  uint8_t index;              /*!< Structure index */
} OTP_DATA_t;

OTP_DATA_t otp_data;

memcpy(otp_data.additional_data, (void*)ADDITIONAL_DATA_PTR, 6);
otp_data.hse_tuning = val & 0x3F;
otp_data.index = OTP_HSE_STR_IDX;

idx = GetOTPFreeIdx();

/* Store OTP structure in OTP area */
 __HAL_FLASH_CLEAR_FLAG(FLASH_FLAG_ALL_ERRORS); /* Clear all Flash flags before write operation*/
   
  err = HAL_FLASH_Unlock();
  err |= HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, STORE_ADDRESS + idx, *(uint64_t*) (&otp_data));

  err |= HAL_FLASH_Lock();
  if (err != HAL_OK) {
    ErrorHandler();
  }

4、校准完成后重新上电获取OTP保存的值并写入HSETUNE[5:0]位域，以后HSE输出的时钟就是校准后的精确时钟

  int32_t idx;
  OTP_DATA_t *potp_data;

  /* Get last calibration index in OTP area
  * if idx<0 it means that no structure with idx=OTP_HSE_STR_IDX has been found in OTP;
  * => so calibration is not done yet
  */
  idx = CheckOTPIndex(OTP_HSE_STR_IDX);
  if (idx >= 0)
  {
    potp_data = (OTP_DATA_t *) (STORE_ADDRESS + idx);
    /* load capacitance value is then set in HSE config register */
    LL_RCC_HSE_SetCapacitorTuning(potp_data->hse_tuning);
    return (HAL_OK);

  }
  else
  {
    return (HAL_ERROR);
  }

当校准之后后续程序启动就只有第4步骤，前123步骤是校准时候需要做的