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CC2420: How does HSSD module work?

Bob Chou
Intellectual 530 points
Part Number: CC2420
Other Parts Discussed in Thread: CC1200

Hi there, 

On the 73 page of the CC2420 datasheet, I found a register named "IOCFG1 (0x1D) – I/O Configuration Register 1". The "HSSD_SRC" bit can be configured to 3 for "Output I/Q after digital down mix and channel filtering". What does this output mean? In what format is this output generated?

I am wondering if this register can be configured to output the I/Q phase information so that I can recover the phase from the I/Q information.

Thanks,

Baofeng

  • 0
    TI__Mastermind 36375 points
    Bob,

    The HSSD_SRC output is a high speed serial output that works as described in the datasheet. It will provide you with I and Q, you will need to calculate the phase of the signal based on the IQ samples. The I and Q samples are serialized at 37.5Mbps. I do have to warn you that the sensitivity of the devices is negatively affected while outputting this signal.

    Overall, I will not recommend using this devices for IQ sampling.

    Can you discuss more about what you need, maybe we have a different device that can help you.

    Regards.
    /TA
  • 0 in reply to TA12012
    Intellectual 530 points
    TA,

    Thanks for your reply!

    I'm doing new development on this old platform because cc2420 is still popular in academia:) I was inspired by the I/Q sampling register from CC1200, which is used by some researchers to recover the frequency and phase information of the received signal and use this information to estimate the carrier frequency offset. Then I found that CC2420 had very similar register: HSSD and ADCTST that has something to do with the I/Q sampling. So I am wondering if I can recover the carrier frequency offset information from this I/Q sample output values from cc2420. But the datasheet is not very clear for me to understand the function of this register.

    I did some reseach on the latest TI's transceiver series and I think they all now take carrier frequency offset estimation and I/Q output as an essential standard configurations. So I thought about utilizing this I/Q sample feature for this purpose and bring some new ideas on this popular transceiver platform.

    Thanks,
    Baofeng