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CC2640R2F: High frequency counting with edge counter

Part Number: CC2640R2F

I need to use a CC26xx counter to determine the frequency of an RF input signal up to 50Mhz.  I could not locate specs on maximum input frequency to the 32-bit counters, but have seen reports of issues with edge counting at 100 kHz, so now this is a bigger concern.

Since I don't require high accuracy (within 10 kHz should be accurate enough), I was thinking of sampling an edge counter every 20 to 50 msecs to determine the frequency of the incoming signal.  I would prefer not to use an external prescaler or Schmitt trigger circuit, as the signal will be at least 3 v p-p.

Is this likely to work up to 50Mhz or will another approach be needed in addition to the CC26xx counter?

  • Hello Rick,
    Please read the note in the TRM section 13.3.2.2 Input Edge-Count Mode. The maximum input frequency for edge detection is ¼ of the system frequency. I can ask some colleagues for advice in case there is any other alternatives.
  • Ok. Thanks Eirik.

    I figured it would be limited.  I decided to prescale down from Mhz to Khz outside the CC2640r2 using a PIC12F675 front ended by a proper Schmitt trigger:

    So should be good now.

    Appreciate the reply.

    Best,

    Rick