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RTOS/CC1310: external Crystal software setting issue

kim hanbeom
Expert 1395 points
Part Number: CC1310

Tool/software: TI-RTOS

I have a question.
I am currently using two external crystals on my custom board.

I saw the following in the reference document:

-A 24-MHz external crystal is required as the frequency reference for the radio. This signal is doubled internally to create a 48-MHz clock. ( X24M_P input and X24M_N output pins.)

-The 32.768-kHz crystal is optional. The low-speed crystal oscillator is designed for use with a 32.768-kHz watch-type crystal. (X32K_Q1 input   and X32K_Q2 output pins)

Each external crystal is connected to a pin. (X24M_P , X24M_N  ,X32K_Q1  , X32K_Q2 )

but I know that I need to set the software in order to use an external crystal.

Can you explain in detail how and where to set it up?

and Is there a way to check if it is actually in use after setting the external crystal?

Thank you.

  • 0
    TI__Guru 58425 points
    Hi Kim,

    You set the crystal source inside the ccfg.c file, look for the "SET_CCFG_MODE_CONF_SCLK_LF_OPTION" which should be set to 0x2 to use the 32.768 crystal. You can the use the "osc" API in driverlib to read out the clock source in application to verify the source (or simply look into the register while debugging).

    dev.ti.com/.../group__osc__api.html
  • 0 in reply to IUsedToBeARealPerson (M-W)
    Expert 1395 points

    My project settings are already set to 0x02.


    I have some questions here.

    I have not modified the clock settings.

    0x2 is the setting for using external clock. Why is 0x2 the default setting?

    If I set it to 0x2, am I using two external clocks?

     

    and I do not know the meaning of this setting.

    What is the difference between the "External LF clock" and the "LF XOSC"?

    Does XOSC mean external crystal and RCOSC mean internal crystal?

     

     

    Thanks 

  • 0 in reply to kim hanbeom
    TI__Guru 58425 points

    Hi Kim,

    I would expect LF XOSC (0x2) to be the default value as the development platforms we provide all use an external 32.768 kHz crystal. 0x2 does not mean you use two external crystal, it means you will be using the LF XOSC.

    The difference between "External LF clock" and "LF XOSC" is that one is an external clock signal source and the other is a crystal source (think oscillator vs crystal). XOSC does indeed mean external crystal, RCOSC is the internal RC-oscillator (not a crystal).

  • 0 in reply to IUsedToBeARealPerson (M-W)
    Expert 1395 points

    To set "LF clock derived from High Frequency XOSC" and "External LF clock", is it necessary to configure the clock source as hardware and set define?

    The documentation says that rf uses 24MHz external crystal 

         ( documnet  : A 24-MHz external crystal is required as the frequency reference for the radio. This signal is doubled  internally to create a 48-MHz clock. )

     

    Will RF use 32.768-kHz external crystal? or use 24-MHz external crystal?

  • 0 in reply to kim hanbeom
    TI__Guru 58425 points
    "To set "LF clock derived from High Frequency XOSC" and "External LF clock", is it necessary to configure the clock source as hardware and set define?"

    I'm not sure that I understand what you are after here. Do you want to derive LF clock from the HF XOSC or use an external LF clock (not LF/HF XOSC)?

    The radio will use the 24 Mhz crystal as cited in your post above.
  • 0 in reply to IUsedToBeARealPerson (M-W)
    Expert 1395 points

    I understand that I use external crystals.

    but I was wondering about the settings of 0x0 and 0x1, so I asked additional questions.

    (How to set s/w and h/w settings for 0x0 and 0x1)

  • 0 in reply to kim hanbeom
    TI__Guru 58425 points
    I'm not sure if I understand what you mean with setting SW and HW settings for these.

    There are some driverlib APIs available to switch between XOSC and RCOSC from inside SW if this is what you are after:

    dev.ti.com/.../group__osc__api.html