Setting Up RTC with LSE and VBAT

[Iman Hosseinzadeh]

Posted on June 10, 2017 at 10:39

I would like to enable the internal RTC of STM32F103 MCU. RTC works fine with HSE clock source. But when I select LSE as clock source, RTC stops working. It is necessary to use LSE and VBAT because the real time should be saved after possible shut down of MCU.

  I use HAL libraries and the settings are made using CubeMX software. I found some code in Standard Peripheral Library. The code works, so the hardware does not have any special problem.

Thanks in advance.

#rtc #vbat #lse #stm32f103

[Imen.D]

Posted on June 12, 2017 at 13:33

Hi

Hosseinzadeh.Iman

,

Can you provide more detailsabout your project and initialization/configuration code.

Be sure to configure your poject with the last version of CubeMX.

Thanks

Imen

[Iman Hosseinzadeh]

Posted on June 15, 2017 at 19:21

Dear Imen,

Thanks for reply.

I upgraded theCubeMX. Here is the code:

RTC_TimeTypeDef sTime,sTime1;
uint32_t bp;
HAL_RTC_Init(&hrtc);
sTime1.Seconds=10;
sTime1.Minutes=20;
sTime1.Hours=17;
HAL_RTC_SetTime(&hrtc,&sTime1,RTC_FORMAT_BCD);
 /* USER CODE END 2 */
 /* Infinite loop */
 /* USER CODE BEGIN WHILE */
 while (1)
 {
 /* USER CODE END WHILE */
HAL_RTC_GetTime(&hrtc,&sTime,RTC_FORMAT_BCD);
sec = sTime.Seconds;
HAL_Delay(1000);
 /* USER CODE BEGIN 3 */
 }
 /* USER CODE END 3 */
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I use the debugger to watch 'sec' variable. This variable does not change.

The Cube-Generated initialization for RTC is here:

static void MX_RTC_Init(void)
{
 /**Initialize RTC Only 
 */
 hrtc.Instance = RTC;
 hrtc.Init.HourFormat = RTC_HOURFORMAT_24;
 hrtc.Init.AsynchPrediv = 127;
 hrtc.Init.SynchPrediv = 255;
 hrtc.Init.OutPut = RTC_OUTPUT_DISABLE;
 hrtc.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
 hrtc.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
 if (HAL_RTC_Init(&hrtc) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
}
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And finally this the clock configuration:

void SystemClock_Config(void)
{
 RCC_OscInitTypeDef RCC_OscInitStruct;
 RCC_ClkInitTypeDef RCC_ClkInitStruct;
 RCC_PeriphCLKInitTypeDef PeriphClkInitStruct;
 /**Configure the main internal regulator output voltage 
 */
 __HAL_RCC_PWR_CLK_ENABLE();
 __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
 /**Initializes the CPU, AHB and APB busses clocks 
 */
 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE|RCC_OSCILLATORTYPE_LSE;
 RCC_OscInitStruct.HSEState = RCC_HSE_ON;
 RCC_OscInitStruct.LSEState = RCC_LSE_ON;
 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
 RCC_OscInitStruct.PLL.PLLM = 25;
 RCC_OscInitStruct.PLL.PLLN = 336;
 RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
 RCC_OscInitStruct.PLL.PLLQ = 4;
 if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 /**Initializes the CPU, AHB and APB busses 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_DIV4;
 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV4;
 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_RTC;
 PeriphClkInitStruct.RTCClockSelection = RCC_RTCCLKSOURCE_LSE;
 if (HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct) != HAL_OK)
 {
 _Error_Handler(__FILE__, __LINE__);
 }
 /**Configure the Systick interrupt time 
 */
 HAL_SYSTICK_Config(HAL_RCC_GetHCLKFreq()/1000);
 /**Configure the Systick 
 */
 HAL_SYSTICK_CLKSourceConfig(SYSTICK_CLKSOURCE_HCLK);
 /* SysTick_IRQn interrupt configuration */
 HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);
}
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