+ Post New Thread
Results 1 to 7 of 7
  1. #1
    Newbie level 3
    Points: 96, Level: 1

    Join Date
    Mar 2019
    Posts
    6
    Helped
    0 / 0
    Points
    96
    Level
    1

    Every few Hours clock running fast rtc1307

    What may be the possible cause for RTC1307 Module(Purchased from Market) running fast approximately 1sec in 3hrs.

    Let me elaborate what I have done,

    My code is in xc8 and internal osc configured in 8mhz at mcu16f887.

    Display is 7segments, data being extracted from RTC1307 (MODULE) with I2C, technique Multiplexed and two button is used for time setting in h/w side. All are going correctly, but

    Once adjusting time with the actual, noticed that after (apprx) 3-4 hours 1-second running fast. Is it the problems of RTC1307 Module or others of my h/w or software.

    As per my opinion that could be only for the cause of RTC module, if so then how do i get rid of that..


    Than u.

    •   AltAdvertisement

        
       

  2. #2
    Super Moderator
    Points: 76,224, Level: 67
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    15,458
    Helped
    3514 / 3514
    Points
    76,224
    Level
    67

    Re: Every few Hours clock running fast rtc1307

    Hi,

    What do you expect from us?
    * If you want us to validate the hardware --> you need to show us
    * If you want us to validate the software --> you need to show us

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



    •   AltAdvertisement

        
       

  3. #3
    Super Moderator
    Points: 80,492, Level: 69
    Achievements:
    7 years registered
    Awards:
    2nd Helpful Member
    betwixt's Avatar
    Join Date
    Jul 2009
    Location
    Aberdyfi, West Wales, UK
    Posts
    13,190
    Helped
    4407 / 4407
    Points
    80,492
    Level
    69

    Re: Every few Hours clock running fast rtc1307

    Do what Klaus suggests first.
    If it is just the clock running fast, the problem is the crystal (or external clock if you are using one) is too high in frequency. That could be because of the crystal itself or the track layout around it. You have to follow the design guidelines in the 1307 data sheet if you want it to be accurate.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



    •   AltAdvertisement

        
       

  4. #4
    Super Moderator
    Points: 258,478, Level: 100
    Awards:
    1st Helpful Member

    Join Date
    Jan 2008
    Location
    Bochum, Germany
    Posts
    45,127
    Helped
    13718 / 13718
    Points
    258,478
    Level
    100

    Re: Every few Hours clock running fast rtc1307

    What does running fast for 1 sec actually mean? How much is the time advancing?



  5. #5
    Advanced Member level 4
    Points: 6,247, Level: 18
    kripacharya's Avatar
    Join Date
    Dec 2012
    Location
    New Delhi
    Posts
    1,209
    Helped
    182 / 182
    Points
    6,247
    Level
    18

    Re: Every few Hours clock running fast rtc1307

    Also what would be useful to know is - what clock are you using to compare this too ? Maybe your reference clock is actually running slow by 1 second per 3 hours !! 1 sec in 3 hours implies ~ 100ppm, which is not good. But then, DS1307 is not known for great accuracy or stability. Check out this writeup.



    •   AltAdvertisement

        
       

  6. #6
    Super Moderator
    Points: 29,544, Level: 41
    andre_teprom's Avatar
    Join Date
    Nov 2006
    Location
    Brazil
    Posts
    8,815
    Helped
    1114 / 1114
    Points
    29,544
    Level
    41
    Blog Entries
    9

    Re: Every few Hours clock running fast rtc1307

    Most 32.768KHz crystals (you did not mention, but it is presumably the one you're using) have good acuracy, ranging from ±5/10ppm up to ±20ppm in the worst cases; however it is possible to find brands with poor specifications of ±50ppm and even of ±100ppm (e.g this), which apparently is the one you have been got; as you took it in the retail, you certainly do not have any reference to the model/manufacturer, and in that case the tip would be to acquire a different one from this one.
    --------------------------------------------------------------------------------------------------
    Part of the world that you live in, You are the part that you're giving ( Renaissance )



  7. #7
    Advanced Member level 4
    Points: 6,247, Level: 18
    kripacharya's Avatar
    Join Date
    Dec 2012
    Location
    New Delhi
    Posts
    1,209
    Helped
    182 / 182
    Points
    6,247
    Level
    18

    Re: Every few Hours clock running fast rtc1307

    It would seem that OP was using an inappropriate reference to check the accuracy. A common noob mistake.



--[[ ]]--