RTC Backup register is not preserved on STM32F4xx within Cube code

[ivan239955_stm1_stmicro_com]

Posted on January 23, 2015 at 11:19

Hello all,

I have a user board with STM32F405VGT6 using RTC (LSE). Firmware is based on STMCubeF4. I have found that RTC loses the time during a power-down although a battery is properly connected to VBAT pin. Then I check the RTC drop-out by a simpler way: testing of a preservation of a mark value in one from the RTC Backup registers. Adapted example STM32F4xx_StdPeriph_Examples\RTC\RTC_BKPDomain works O.K. (as LEDs show) but the same procedure based on HAL drivers and Cube code (see bellow) does not. I have found that it works without the SystemClock_Config function. If the function is inserted either in 1st or 2nd position, the backup register is preserved after reset but not after power-down. It is very strange, isn't it? I cannot debug the function immediatelly after power-up, since the JTAG adapter has to be initialized sooner. Does anybody has any opinion? Thank you. Ivan

#define BACKUP_MARK 12345678
#define BACKUP_TEST_REG 19
#include ''stm32f4xx_hal.h''
static void MX_GPIO_Init(void);
static void SystemClock_Config(void);
// Macro -------------------------------------------------------------
#define SETPIN(port,pin) (port->BSRRL = pin)
#define CLRPIN(port,pin) (port->BSRRH = pin)
// Pin definitions
#define LED_B_PIN GPIO_PIN_12 // modra LED
#define LED_DR_PIN GPIO_PIN_14 // cervena z dvojite LED
#define LED_DG_PIN GPIO_PIN_13 // zelena z dvojite LED
#define LED_PORT GPIOE
RTC_HandleTypeDef hrtc;
//------------------------------------------------------------------------------
int main(void)
{
HAL_Init();
// SystemClock_Config(); // Pos #1, causes reset of Backup Register if the power has been off
MX_GPIO_Init();
__PWR_CLK_ENABLE(); // normally in SystemClock_Config()
HAL_PWR_EnableBkUpAccess();
if (HAL_RTCEx_BKUPRead(&hrtc, BACKUP_TEST_REG) == BACKUP_MARK)
SETPIN(LED_PORT, LED_B_PIN); // blue LED ON, if the backup value persists
else
SETPIN(LED_PORT, LED_DR_PIN); // red LED ON, if the backup value dismisses
// SystemClock_Config(); // Pos #2, causes reset of Backup Register if the power has been off
__HAL_RTC_WRITEPROTECTION_DISABLE(&hrtc); // set the backup register
HAL_RTCEx_BKUPWrite(&hrtc, BACKUP_TEST_REG, BACKUP_MARK);
__HAL_RTC_WRITEPROTECTION_ENABLE(&hrtc);
HAL_PWREx_EnableBkUpReg(); // turn on VBAT regulator
while (1);
}
// System Clock Configuration ----------------------------------------------
void SystemClock_Config(void)
{
RCC_ClkInitTypeDef RCC_ClkInitStruct;
RCC_OscInitTypeDef RCC_OscInitStruct;
__PWR_CLK_ENABLE();
__HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);
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 = 8;
RCC_OscInitStruct.PLL.PLLN = 336;
RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
RCC_OscInitStruct.PLL.PLLQ = 7;
HAL_RCC_OscConfig(&RCC_OscInitStruct);
RCC_ClkInitStruct.ClockType = 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_DIV2;
HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5);
}
//----------------------------------------------
void MX_GPIO_Init(void)
{
GPIO_InitTypeDef GPIO_InitStruct;
__GPIOE_CLK_ENABLE();
/* Configure GPIO pins : LEDs */
GPIO_InitStruct.Pin = GPIO_PIN_12|GPIO_PIN_13|GPIO_PIN_14;
GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_LOW;
HAL_GPIO_Init(GPIOE, &GPIO_InitStruct);
}