PropBasic and RTC

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Comments

  • The clock gains two seconds a week making the error 114 seconds per year.

    My $40 Timex wrist watch is accurate to one minute a year. The wrist watch is kept at a relatively constant temperature due to its location on my wrist.

    I am sure that the crystal is temperature sensitive and has xxx parts per million sensitivity. I might be able to rig a miniature temperature sensor and heating element on the crystal and run experiments.

    Discovery
  • Discovery wrote: »
    The clock gains two seconds a week making the error 114 seconds per year.

    My $40 Timex wrist watch is accurate to one minute a year. The wrist watch is kept at a relatively constant temperature due to its location on my wrist.

    I am sure that the crystal is temperature sensitive and has xxx parts per million sensitivity. I might be able to rig a miniature temperature sensor and heating element on the crystal and run experiments.

    Discovery

    That's well within specs, even better than I have gotten. Just reset the clock every six months.
    Infernal Machine
  • If the drift is consistent (more or less) then you could also change the number of cycles per second from 80_000_000 to something else. If you're gaining two seconds per week then perhaps 79_999_750 or so would compensate.

    But as Publison said, 114 seconds per year isn't bad at all. If you really need more accurate timing then you'll probably need a GPS module.
  • I have only every used incredibly cheap crystals that were highly affected by PCB capacitance. Usually, I am timing things in the "minutes" order of magnitude. So, 3.3ppm is a dream to me. It is an open-loop system, after all.
  • Failure is not an option...it's bundled with the software.
  • Thanks for the information.

    Setting the cycles to 79_999_750 looks good...I will try that.

    Also, the chances are fairly good that I may have to make a parameter change in 6 months so the clock will be reset.

    Very good.

    Discovery
  • The Propeller Activity Board clock is under test with 79_999_750.

    Discovery
  • It appears that the Propeller Activity Board clock is running even faster with the change to 79_999_750.

    So, I will run another test with the setting at 80_000_250.

    Discovery
  • It appears that changing the 80_000_000 term does not affect the clock speed significantly.

    The clock runs fast whether the term is reduced by 250 or increased by 250.

    I may make a large change in the term as another test.

    Discovery
  • why should changing the clock speed of the propeller change the crystal based frequency of the rtc-chip?

    curious

    Mike
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  • msrobots wrote: »
    why should changing the clock speed of the propeller change the crystal based frequency of the rtc-chip?

    curious

    Mike

    It will not affect an rtc chip clock, but it could affect an rtc object running in a cog if the frequency setting was used in the timing calculation. I suspect that is not the case here.

    Since the clock gains two seconds a week (or 2s every 604800s) it might be better to increase the number of cycles counted for incrementing the seconds from 80,000,000 to 80,000,265 counts. That change would need to be made to the rtc object.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • PS - is this Propeller RTC Emulator the object you are using?
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
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