Posted on September 05, 2013 at 10:22From example code given in STM32F2 , I used RTC example & use it with LSI.
I have 3V on Vbat pin. I found that when VDD gets removed LSI oscillator gets off also, even if Vbat is present. Is it property of LSI or I am making some mistake in correct operation of RTC. However once RTC_BKP_DR0 is written on initialization , it maintains its value.
void rtc(void)
{
RTC_InitTypeDef RTC_InitStructure;
RTC_TimeTypeDef RTC_TimeStructure;
RTC_DateTypeDef RTC_DateStructure;
if(RTC_ReadBackupRegister(RTC_BKP_DR0) != 0x32F2)
{
/* RTC configuration */
RTC_Config();
/* Configure the RTC data register and RTC prescaler */
RTC_InitStructure.RTC_AsynchPrediv = AsynchPrediv;
RTC_InitStructure.RTC_SynchPrediv = SynchPrediv;
RTC_InitStructure.RTC_HourFormat = RTC_HourFormat_12;
/* Check on RTC init */
if (RTC_Init(&RTC_InitStructure) == ERROR)
{
while(1);
}
RTC_TimeRegulate();
}
else
{
/* Check if the Power On Reset flag is set */
if(RCC_GetFlagStatus(RCC_FLAG_PORRST) != RESET)
{
// printf(''\r\n Power On Reset occurred....\n\r'');
}
/* Check if the Pin Reset flag is set */
else if (RCC_GetFlagStatus(RCC_FLAG_PINRST) != RESET)
{
//printf(''\r\n External Reset occurred....\n\r'');
}
/* check if LSI is on */
AsynchPrediv = RCC->CSR; /* return zero in LSB indicating LSI is off */ /* Enable the PWR clock */
RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR, ENABLE);
/* Allow access to RTC */
PWR_BackupAccessCmd(ENABLE);
/* Wait for RTC APB registers synchronisation */
RTC_WaitForSynchro();
}
while(1)
{
configure_tim3_wait( 100000 );
RTC_GetTime(RTC_Format_BIN, &RTC_TimeStructure);
RTC_GetDate(RTC_Format_BIN, &RTC_DateStructure);
}
}
