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Original question:

CC1201: CC120x and CORDIC Module

CC1201: CC1201 RX BW and CORDIC Samples

Rui Gomes67
Prodigy 165 points
Part Number: CC1201


Hi.

I am trying to use the CC1201 to retrieve  angle samples from the CORDIC at a data rate of 100 kHz. However, the RX bandwidth is 833.33kHz (direct down-conversion), which means that the ADC sample rate and CORDIC update rate is much higher than 100 kHz. Am I able to read the CORDIC angle without problems? I am asking this because the angle register is distributed between two registers. If I read one register at the time, is there any possibility that the data changes in the mean time?

Thank you for your attention.

Regards

  • 0
    TI__Guru 67551 points

    Please see the section 3.2.4 and 8.6 regarding fifo access in the SWRU346 users guide.

    Regards,

    Chris 

  • 0 in reply to Chris Sterzik
    Prodigy 165 points

    Hi,

    I am already familiar with the datasheet, and neither of those two sections clarifies my question. Furthermore, the access to the CORDIC samples is not performed through the FIFO. Also, I tried reading the CORDIC registers in burst mode, which should be possible, but I could not obtain useful data. Hence, my question remains the same: If the CC1201 is sampling the signal at much faster rate than the speed I can read the CORDIC registers through SPI, will I have any problem reading the sample and magnitude registers given that the data is stored in two different registers (assuming that I am not reading in burst mode)?

    Thanks

  • 0 in reply to Rui Gomes67
    TI__Guru 67551 points

    Hello,

        What are you trying to do with the Cordic data?  What is the end goal?

    Regards,
    Chris

  • 0 in reply to Chris Sterzik
    Prodigy 165 points

    Trying to implement a custom 4-QAM demodulation. 

  • 0 in reply to Rui Gomes67
    TI__Guru**** 317180 points

    Normally QAM would require a linear PA (not sure when you only do 4). What  do you want to gain using 4-QAM compared to 4-FSK? Just trying to understand the objective.

  • 0 in reply to TER
    Prodigy 165 points

    Indeed the PA needs to be linear to support 4-QAM in transmit mode. However, I intend to use the CC1201 to (RX) receive the data only. We intend to use 4-QAM because M-QAM it is more spectrally efficient, and we want to support several M-QAM modulations in the future. Thus, we want to begin with 4-QAM.

    Can you help me with my question? How can I retrieve the CORDIC data and be sure about data integrity?

    With best regards

  • 0 in reply to Rui Gomes67
    TI__Guru 67551 points

    Hello,

        I am not aware of any information or testing that would provide certainty about the data integrity.  I am going to close this thread and leave as unresolved.  Thank you for the question as this helps identify gaps in our collateral and my understanding.

    Regards,

    Chris