Posted on November 28, 2016 at 10:59Hi,
I'm using STM32L476RG microcontroller and I'm configuring the RTC to get the instant time value. I'm using LSE with 32,786 KHz as a clock source for my RTC . I have followed this application note (
http://www.st.com/content/ccc/resource/technical/document/application_note/group0/71/b8/5f/6a/8e/d5/45/0a/DM00226326/files/DM00226326.pdf/jcr:content/translations/en.DM00226326.pdf
) to set correctly the initialization process as well as the PREDIV_SYNCH and PREDIV_ASYNCH values (which are respectively in my case 0x00FF and 0x7F ) . However, when I let my application run for too long ( 24 Hours ) and then I check the RTC Time value , I found a gap of 10 seconds ( difference between my RTC time and the desktop time ). This difference is so huge for me because I'm working on medical app.
Here's my Init function:
&sharpdefine RTC_ASYNCH_PREDIV 0x7F
&sharpdefine RTC_SYNCH_PREDIV 0x00FF
BSP_RTC_Status Status= RTC_OK;
/**** Configure the RTC peripheral ******************/
/* Configure RTC prescaler and RTC data registers */
/* RTC configured as follow:
- Hour Format = Format 12
- Asynch Prediv = Value according to source clock
- Synch Prediv = Value according to source clock
- OutPut = Output Disable
- OutPutPolarity = High Polarity
- OutPutType = Open Drain */
__HAL_RTC_RESET_HANDLE_STATE(&RtcHandle);
RtcHandle.Instance = RTC;
RtcHandle.Init.HourFormat = RTC_HOURFORMAT_12;
RtcHandle.Init.AsynchPrediv = RTC_ASYNCH_PREDIV;
RtcHandle.Init.SynchPrediv = RTC_SYNCH_PREDIV;
RtcHandle.Init.OutPut = RTC_OUTPUT_DISABLE;
RtcHandle.Init.OutPutPolarity = RTC_OUTPUT_POLARITY_HIGH;
RtcHandle.Init.OutPutType = RTC_OUTPUT_TYPE_OPENDRAIN;
if(HAL_RTC_Init(&RtcHandle)!= HAL_OK)
{
Status = RTC_ERROR;
}
__HAL_RTC_WRITEPROTECTION_DISABLE(&RtcHandle);
RtcHandle.Instance->CR |= RTC_CR_BYPSHAD;
/* Enable the write protection for RTC registers */
__HAL_RTC_WRITEPROTECTION_ENABLE(&RtcHandle);
Any ideas please ?
#rtc #l4 #time #stm32
