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CC1200 AGC freeze for transparent Mode / synchronous serial

S C70
Prodigy 210 points
Other Parts Discussed in Thread: CC1200

Hi,

I need to communicate with a device (very short range - 10cm) whose properties are unknown appart from frequency. (bit rate and packet format unknown).

For this, I use CC1200 in Fifo mode, by oversampling data ( 50K for oversampling 5Kbps signals). (Fifo mode with no preamble - sync word).

My issue, is that I do not know how to freeze AGC when CS is detected.

I guess that the issue is very similar for application using transparent mode and synchronous serial.

How do you freeze AGC, (based on CS detection I guess) when you use these modes?

Do you have to access AGC registers, or is there a soft sync commmand? Are there examples of transparent/serial modes applications?

Thanks

BR

     S.C.

  • 0
    TI__Mastermind 39860 points
    Why do you need to freeze the gain at CS detection?

    For 10 cm range I suggest you minimize the maximum gain (AGC_CFG2). That is, set it fixed so that max gain is equal to min gain (AGC_CFG3). AGC_CFG2.AGC_MAX_GAIN = AGC_CFG3.AGC_MIN_GAIN = 0x11
  • 0 in reply to Sverre
    Prodigy 210 points

    I just saw my issue. Since I have no sync word and no preamble, I do need to synchronise.

    And I did not see in the user guide what you describe as "Blind mode"

    So I guess I need to perform External syncrhonisation by external GPIO, with EXT_SYN_DETECT active.

    ==> How shall it be used (Asserted when sync detectged == Pulled low?)

    When you set this GPIO, what exactly does the CC1200? Does it only freeze AGC? In this case, since I'm 10cm, AGC_Min = AGC_Max would do the same as EXT_SYNC_DETECT?

    Is it possible to perfom blind mode with data read from FIFO, and not from Serial Link?

    Thx

    BR

  • 0 in reply to S C70
    Prodigy 210 points
    Hi,
    Sorry, but i would really need a quick answer on these please :)
    ==> How shall I use EXT_SYNC_DETECT for blind mode ( which registers shall be set, what is status of GPIO2 (1=freeze AGC / 0 = free AGC)?
    ==> Do we need AGC_SYNC_BEHAVIOR = 001 ?
    ==> How can we monitor that Sync event is handled
    When AGC is "free"; I clearly see noise when no signal, but data is ok when signal is present
    By setting AGCMin = AGCMax I would have expected a lowered noise.
    What does Sync perform appart from AGC Freeze?
    Thx