Measuring a crystal PPM

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    Question: What do I need to do to measure crystal PPM?

     

    Answer:

    After powering up the radio, write 0x20 to XTAL_CTRL_ADR register.  Then use a high precision frequency counter (HP53181A or eq.) to measure crystal PPM via the XOUT pin:

      // XTAL_CTRL_ADR=0x20 - drives 12MHz onto XOUT pin
      RadioWrite(0Ch,20h);

    Expect the measurement to be within the 11,999,640Hz to 12,000,360Hz range. If the measurement falls outside the expected range verify that the crystal's load capacitance is 10pF.