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CC1310: CC1310 RTC accuracy

Archil Pirmisashvili
Prodigy 90 points
Part Number: CC1310

Hello,

We have an NoRTOS application that needs accurate RTC on CC1310 chip.

Previously we used LF_RCSOC as clock source (configured in ccfg.c) and got very big drift. So we decided to use external crystal to get more accurate RTC.

So we put external 32kHz crystal (taken from CC1310-Launchpad) and set ccfg.c to LF_XOSC as clock source. But unfortunately we got the same results in accuracy.

May be we need to make some additional calibrations? But we haven't found any explanation how to do it.

Please suggest us how to fix the issue.

Thank you,

Archil

  • 0
    TI__Guru* 79271 points

    I would expect the accuracy to be better when using the 32-kHz crystal oscillator compared to the RC oscillator.

    How are you actually testing this (please provide a small test program) and what accuracy are you measuring in the two cases?

    Also, what do you mean by "we put external 32kHz crystal (taken from CC1310-Launchpad) and set ccfg.c to LF_XOSC as clock source"

    Does this mean that you are measuring on some custom HW? Are you using correct values for the load cap's?

    Do you see the same thing when you are doing the same test on the CC1310LP and use the crystal?

    Siri

  • 0 in reply to Siri
    Prodigy 90 points

    How are you actually testing this (please provide a small test program) and what accuracy are you measuring in the two cases?

    We are comparing RTC value (AONRTCSecGet function) to current time once it was taken and after 1 day.

    Does this mean that you are measuring on some custom HW? Are you using correct values for the load cap's?

    Yes we use custom HW and we use correct values for load cap's.

    Do you see the same thing when you are doing the same test on the CC1310LP and use the crystal?

    We will try to check it on CC1310LP and update you ASAP.

  • 0 in reply to Archil Pirmisashvili
    TI__Guru* 79271 points

    If you have the same problem on our HW, please provide a complete demo code that will demonstrate the problem, so that we can try to reproduce it.

    We also need info regarding what accuracy you are measuring to know if this is as expected or not.

    Siri

  • 0 in reply to Siri
    Prodigy 90 points

    We've made additional test with our HW and got 57ppm. Is is possible to calibrate it to be more accurate?

  • 0 in reply to Archil Pirmisashvili
    TI__Guru* 79271 points

    What is the accuracy of the 32 kHz crystal you are using? You will not get better accuracy than this.

    Siri