7 Replies Latest reply on Oct 16, 2014 5:52 AM by miko_283856

    RTC DST related problem






      I'm using the DST option of the RTC component (PSoC5LP CY8C5868AXI-LP035) in this way:


                          RTC_WriteDSTStartHour(1);                                                                   // + 1 at 01:00 last Sunday of March
                          RTC_WriteDSTStartWeek(5);                                                                   // last week of March
                          RTC_WriteDSTStopHour(1);                                                                    // - 1 at 01:00 last Sunday of October
                          RTC_WriteDSTStopWeek(4);                                                                    // Last week of October                    RTC_WriteDSTStopMonth(OCTOBRE);
                          RTC_WriteDSTOffset(60);                                                                     // 60-minute delay
                          RTC_WriteDSTMode(1);                                                                        // Relative


      When I set the date & time for the last Sunday of March, at 01:00 the time is correctly incremented by 60 minutes (01:00 => 02:00).


      However when I set it for the last Sunday of October, at 01:00 the time also shift to 02:00. However I expect to read 00:00.


      Am I missing something in the DST setup above?





        • 1. Re: RTC DST related problem

          Ooop's slight problem writing my previous thread.




          In the 2nd test, the time is neither incremented, nor decremented by 60 minutes. So shifting from 00:59 to 01:00 does in fact nothing which is still uncorrect.


          Apologize for this mistake.



          • 2. Re: RTC DST related problem

            Hmm, the clock should jump from 1:59 to 1:00. So your obviously in the wrong timezone for your test :)

            • 3. Re: RTC DST related problem

              Hi Hli,


              Thanks for the reply, you're correct I'm wrong compared to European specs.


              However, there is no direct relation as the shift is checked by the RTC firmware which applies intenal comparisons between the current time and the DST settings.


              So even if my DST triggering hours are false, there is no reason not to correctly run with these values.




              I'm now refering to this paragraph in the RTC component datasheet ():


              'RTC_STATUS_DST – Status of Daylight Saving Time. This bit goes high when the current
              time and date match DST time and date and the time is incremented. This bit goes low after
              the DST interval and the time is decremented.'


              Resetting the bord and setting the time one minute before DSTStop showed that the RTC_STATUS_DST was 0 before the shift and went to 1 after.


              So this behavior follow the 1st part of the above stated rule. However setting the RTC time between March and October should have raised it in the RTC initialization. This wasn't the case.


              Currently in this kind of situation it seems my RTC is running upside-down with respect to this status bit.


              I should state that I first start the RTC component without filling its registers, I then set the DST registers and a while after thru the use of a PC dedicated software and the USB link, I setup the date & time framed by the RTC_Disable/EnableInt. May be I should start the RTC after all this setup to have the RTC-STATUS_DST bit correctly initialized?


              Any idea?

              • 4. Re: RTC DST related problem

                What I meant is: on the last sunday of october, the time flows normally from 00:59 to 01:00 (this is what you tested and its correct). But then it jumps from 01:59 back to 01:00 - and you don't seem to have tested that.


                According to the datasheet, a relative start/stop date for DST is converted to a fixed date at the end of the first hour after _Start() has beend called (and then one year after that). So your test routine should accomodate for that. (Maybe you can, for testing purposes, set a fixed DST start/stop date instead of a relative one. Dont forget to enable DST functionality when setting the mode register)

                • 5. Re: RTC DST related problem

                  Sorry when I confuse you, but the time switchback is at 03:00h to 02:00h for the EU.


                  Nonetheless your observed behaving make me think, if the RTC is accepting an UTC which is then correctet according to your set timezone.





                  • 6. Re: RTC DST related problem

                    Since the original test was that DST turns on at 01:00, I was assuming that it works according to UTC.

                    • 7. Re: RTC DST related problem

                      Hli & All,


                      Bugs corrected.


                      In fact once more I was interpreting the datasheet without strictly applying what is written.


                      After having dug deeper into it, I made the following evolution for each update sent by the PC:


                                          RTC_currentTimeDate.DayOfMonth = xxx;
                                          RTC_currentTimeDate.Month      = xxx;
                                          RTC_currentTimeDate.Year       =   xxx;
                                          RTC_currentTimeDate.Hour       = xxx;
                                          RTC_currentTimeDate.Min        = xxx;
                                          RTC_currentTimeDate.Sec        = 0;

                                          RTC_WriteDSTMode(RTC_DST_ENABLE | RTC_DST_RELDATE);
                                          RTC_WriteDSTStartHour(2);                                                 // 01:59 => 03:00
                                          RTC_WriteDSTStopHour(3);                                               // 02:59 => 02:00
                                          RTC_Init();                                                                              // Mandatory for each update to be applied correctly


                      I may close this post, everything works right now (but wasn't really a piece of cake, a real good example would have help and save time ...)