2021-07-03 10:03 PM
void SystemClock_Config(void)
{
RCC_OscInitTypeDef RCC_OscInitStruct = {0};
RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};
RCC_PeriphCLKInitTypeDef PeriphClkInit = {0};
/** Configure the main internal regulator output voltage
*/
__HAL_PWR_VOLTAGESCALING_CONFIG(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_LSI
|RCC_OSCILLATORTYPE_HSE;
RCC_OscInitStruct.HSEState = RCC_HSE_ON;
RCC_OscInitStruct.HSIState = RCC_HSI_ON;
RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
RCC_OscInitStruct.LSIState = RCC_LSI_ON;
RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
RCC_OscInitStruct.PLL.PLLMUL = RCC_PLLMUL_3;
RCC_OscInitStruct.PLL.PLLDIV = RCC_PLLDIV_3;
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_HSE;
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_1) != HAL_OK)
{
Error_Handler();
}
PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART1|RCC_PERIPHCLK_I2C1
|RCC_PERIPHCLK_RTC|RCC_PERIPHCLK_USB;
PeriphClkInit.Usart1ClockSelection = RCC_USART1CLKSOURCE_PCLK2;
PeriphClkInit.I2c1ClockSelection = RCC_I2C1CLKSOURCE_PCLK1;
PeriphClkInit.RTCClockSelection = RCC_RTCCLKSOURCE_LSI;
PeriphClkInit.UsbClockSelection = RCC_USBCLKSOURCE_PLL;
if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInit) != HAL_OK)
{
Error_Handler();
}
}
Ams this ias code of RTC.c
2021-07-04 01:57 AM
LSI is a very imprecise clock source, see datasheet. You can "calibrate" it by changing the asynchronous and synchronous pedalers, but it will never be stable and precise.
JW
2021-07-04 02:14 AM
so what is the best option to go with?
2021-07-04 02:29 AM
Best option for what?
To maintain real time, you need to use LSE and a 32.768kHz crystal.
If you have a crystal on HSE and you don't want to use some of the low-power modes (in some of which LSI doesn't work either, btw.), you can derive the RTC clock from HSE too.
JW