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FREQOFF KHz Calibration CC1101

Zebryk
Expert 1240 points
Other Parts Discussed in Thread: CC1101

Hello,

For a 26MHz crystal, what is FREQOFF calibrated to in KHz?

If the default is binary 0, how is +/- indicated?

I would like to apply an offset by measuring the transmit frequency error with a spectrum analyzer.

(The app notes describe applying FREQEST but do not detail the engineering units.)

Thanks,

Jay Zebryk

  • 0
    TI__Mastermind 39860 points

    Please refer to page 90 in the CC1101 data sheet, register FREQEST. The estimated frequency offset is a 2's complement number and the resolution is crystal frequency/2^14.

  • 0 in reply to Sverre
    Expert 1240 points

    Simply repeating the contents of the data sheet's cryptic description is of little help towards understanding how to utilize this function.

    Assumming that the result of 26,000,000 / 16,384 = 1586.9140625 is distributed over a 8 bit range or 1587Hz per bit, we plan to firstly measure the TX CW frequency without any offset to find a baseline. Next, we plan to apply increments/decrements in 10Bit steps whilst recording the changed carrier frequency. This may provide confirmation as to whether this function behaves as we speculate. Hopefully this should work out to the +/-202KHz (203.125) metioned in the data sheet.

    Very time consuming reverse engineering these things.