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CC2540: CC2540 32K crystal oscillator frequency test

Expert 1910 points

Replies: 5

Views: 69

Part Number: CC2540

Whether the 32K crystal oscillator of CC2540 can be measured through GPIO port, just as CC2640 can output the actual frequency through IO port.

How to optimize the ppm for 32K crystals

  • Guru 240310 points

    The frequency tolerance is given by the xtal so if you need a smaller ppm number you have to find a xtal with smaller tolerance. 

    The center frequency will also be dependent on the load caps to the xtal. If the center frequency is off always in one direction it's possible to adjust the load cap slightly to tune the center frequency.

     OOO until September 30th. If your thread is not answered by someone after 2-3 days after your last post, please repost with a link referring to your original post. 

  • In reply to TER:

    “If the center frequency is off always in one direction it's possible to adjust the load cap slightly to tune the center frequency"

    How should "the center frequency" be tested

  • Guru 240310 points

    In reply to Hank Zhang:

    As you wrote you can get the 32 kHz signal out on a pin. The method will depend a bit with regards to which instrument you have in hand but you have to measure the frequency of this signal and get it to be as close to the wanted frequency as possible. 

     OOO until September 30th. If your thread is not answered by someone after 2-3 days after your last post, please repost with a link referring to your original post. 

  • In reply to TER:

    That's the problem, which pin.Can GPIO output this 32K frequency?I have a frequency meter

  • Guru 240310 points

    In reply to Hank Zhang:

     OOO until September 30th. If your thread is not answered by someone after 2-3 days after your last post, please repost with a link referring to your original post. 

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