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CC1120 Time From Start RX Until Valid RSSI

KAZUHIKO TAKRYAMA
Prodigy 110 points
Other Parts Discussed in Thread: CC1120

We are developing a apparatus using CC1120.

The 14 page of the application note "swrs112b" have the following description.
 *Time From Start RX Until Valid RSSI: 4.6ms (12.5 kHz channels)

But we need to read the RSSI at a faster than 4.6ms. (We need to read below 2ms)
We want to know only the RSSI value, the signal is not read rightly.

I set the following register.
 - AGC_CFG0.RSSI_VALID_CNT: minimum
 - AGC_CFG1.AGC_SETTLE_WAIT: minimum
 - AGC_CFG1.AGC_WIN_SIZE: minimum
 - CHAN_BW.ADC_CIC_DECFACT: minimum

The BB_CIC_DECFACT(RX BW:25kHz) is not change, because of adjacent channel interference.

Please advise us the setting of the other register for fast readout of the RSSI.

Thanks.

  • 0
    TI__Guru* 86731 points

    Hi

    There have been some changes to the user guide regarding the equations used to calculate the Max CS response time. Please see the attachment. The new User guide will be available on the web next week.

    BR

    Siri

    6428.RSSI.pdf

  • 0 in reply to Siri
    Prodigy 145 points

    Hi Siri,

    I am also getting problem while getting right RSSI value. I am programming using LabView. My procedure to get RSSI value is as follows:

    1. I send 0x34 strobe to start RX mode.

    2. I send in series: 0x2F OR 0x80, 0x71, 0x0 to get RSSI[11:4]

    3. then I send in series: 0x2F OR 0x80,0x72,0x0 to get RSSI[3:0]

    Now I am getting integer value 67 from RSSI0 till my input signal strength is from -120 db to -40 db. For the value below -40 db, I get integer value 71 on the same register.

    I am getting integer values ranging 229-260 from RSSI11:4] till my input signal strength is from -120 db to -40 db. For the value below -40 db, I get integer values ranging 0-10 on the same register.

    I also do not understand the calculation about how 0x200 is interpreted as 32 dbm and how 0x3A0 as -70 dbm.

    Please help me regarding this problem.

    Thanking you,

    BR

    Shishir