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I/Q data on CC253x

David Oswald
Prodigy 70 points

Other Parts Discussed in Thread: CC2530

Hi,

I'm planning to access the (raw) I/Q baseband data on CC253x. This appears to be possible on CC253x (cf. page 269 in the user's guide http://www.ti.com/lit/ug/swru191f/swru191f.pdf, using register ADCTEST2), however, it was not clear to me to which pins the signal is output, in which format the data is, and so on.

Is the CC253x similar to a CC1101(http://e2e.ti.com/support/rf__digital_radio/etc_rf/f/228/p/134903/514228.aspx), where one gets the delta-sigma bitstream directly after the downconverter?

Thanks,

Best

David

  • 0
    TI__Mastermind 36415 points

    This is a feature that has been included for the sole purpose of debugging and optimizing the IF-ADC. Hence, it is not well documented. On the CC2530 it is possible to extract the I/Q data using the settings provided in the User Guide, however please note that you will see a severe effect on the RF performance. We have noted an RX performance degradation of approximately 30dB, effectively rendering this interface useless for anything else but debug.

    Regards,
    /TA

     

  • 0 in reply to TA12012
    Prodigy 70 points

    Hi,

    thanks for the info. For our particular purpose, a 30dB degradation may actually be acceptable. I assume the data is then output as the delta-sigma bitstream (when using the appropriate settings for ADCTESTx)? Which pins are used for this?

    Thanks

    David

  • 0 in reply to David Oswald
    TI__Mastermind 36415 points

    David, 

    I am sorry that information is not really well documented anywhere. I believe it has to be selected thru the "RFC_OBS_MUX0" register. There is an option there to get random data from the RF ADC see, "rfc_rand_q" register. However there is no mention of getting the I/Q data out, but I believe it is contained in the 20 or so "reserved" registers.

    I am looking into the design documentation on this device to try to extract what the remaining options are, this will take some time. In the mean time it might also be an option for you just to go down the list and see if one works.

    This register will connect the internal signal to one of 5 IO on the CC2530 as documented in the UG, this is where the IQ signal will appear.

    Regards,
    /TA

  • 0 in reply to TA12012
    Prodigy 70 points

    Hi,

    great, thanks, we'll try that, if we happen to find this out before you do I'll post this info here.

    Best

    David