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CC1120: RSSI value is not accurate enough

Allen Tang26
Prodigy 240 points
Part Number: CC1120

Hi,

I am developing the driver to manipulate the CC1120 chip.

My problem is that I can not get an accurate RSSI value which is provided by the register RSSI1(0x2f71) and RSSI0(0x2f72).

As the datasheet says the resolution of the RSSI is 0.0625dB, but I can not see a one bit change of the RSSI0 register[6:3].

The RSSI_OFFSET is configured around -102dB and CS_THRESHOLD is 0x18, RSSI_VALID_CNT = 2.

How to achieve the designed 0.0625dB resolution?

Thanks

Allen

  • 0
    TI__Genius 11810 points
    Hi Allen,

    Even if the resolution is 0.0625 dB, the actual accuracy is not that good. Typical accuracy is 1-2 dB. Do you get something in that range?

    -Simon
  • 0 in reply to Simon J
    Prodigy 240 points

    Thanks Simon,

    Understand that the absolute accuracy is 1-2 dB, that is fine.

    I am expecting to get a better relative accuracy of the RSSI change.

    For example, if the input signal is -6.25 dB, the read RSSI maybe -7.25 dB.

    Then the input signal changes to - 5.25 dB, are we going to read the - 6.25 dB?

    Are there any configuration to the CC1120 to enable the LSB 4 bits of RSSI to be activated and following the RSSI change well?

    Thanks

    Allen

  • 0 in reply to Allen Tang26
    TI__Guru**** 317180 points
    No,
    what you will see is if you input, lets say -50 dBm, from a signal generator the 4 LSB bits will just give random values.