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AFE5809EVM: Demodulator

Mateo Recalde
Intellectual 290 points
Part Number: AFE5809EVM
Other Parts Discussed in Thread: AFE5809

Hello,
            I am testing the demodulator of the afe5809evm, below I detail some configurations that so far I am taking into account, I have already read the manual (TIDU702, SLOS738E, SLOU338A) and I have not satisfactorily obtained good results, it will be for my little experience in some concepts, but I am making the effort to understand this, below I show some captures regarding my configuration,

Regarding to the ADC block, I have not had major problems, I have been able to get my echo signal without problems.

 

Unfortunately, when I made settings for the demodulator block, I get results similar to the image below


 

I look forward to a specific help, I would appreciate it.

Regards,

  • 0
    TI__Expert 6040 points

    It is good news you can make the ADC run and see echos.  the problem you faced is the demod configuration.  right coefficents and other settings are required. Plus some hardware. 

    I noticed that there may not have SYNC word 0x2727 comes out from your capture. Thus i feel there is a missing TX_SYNC signal. In the user manual, we require to have ADC CLK, TX_SYNC, Signal source are correlated.  see Figure 10. Hardware Setup for Demodulation Mode Capture

    2. I saw your are using the Decimation of 32. Thus you will need to load the M=32 coefficients. 

    3. after demod, you will need to run a post-processing in the AFE5809 GUI. HSDC Pro only shows raw data with many channel compressed on the same LVDS. Thus is a little bit difficult to see each channel data from the raw capture. 

    in order to make sure everything is OK on the EVM side. i would suggest you follow the user manual and make the test mode working first. for example, 

    there is a Demod M=4 I/Q Test Mode under test mode tap.  TI EVM GUI will load the coefficents and other setttings. you can run the EVM GUI to post-process the data.  as for the signal concerned, I think you can use a 2-CH funtional generator first. 

    After that, you can feed your echo signal in, assume echo signal is synchronized with ADC clock. 

    hope it helps. 

    Thanks!

  • 0 in reply to Xiaochen (Sean)Xu
    Intellectual 290 points

    I really appreciate your help dear Xiaochen, I realise that I have some troubles beacuse it still very unclear for me some definitions and the user manual isn't friendly to me, but I am continuing with my testing.

    Now I have one particulary problem is that I generate the trigger PRF from a FPGA, this trigger is about 10ms separated, this signal is conected to the AFE TSW and my signal generator, this generator generate 3 sinusoidal burst of 200 mVPP, unfortunally inside the TSW i can see only the first capture that is the first incoming trigger signal, I set up the trigger option mode in HSDC pro GUI, reading the manual it says that I can capture all of the trigger but it is no real.

    I will be thankful if you guys can helpme with this.

  • 0 in reply to Mateo Recalde
    TI__Expert 6040 points

    The Trig is 10ms. the TSW1400 has limited memory for saving all data points. That could be the reason why you only see one capture. if you run the ADC at 40MSPS, 10ms means 400K points.  the TSW will repsond to the first trig, then capture the points your entered. If you want to capture more, then you need to adjust the capture points in the TSW setting. typically for evaluation purpose, the first capture should be OK since we assume that all following signals are the same. 

    when Trig is not sync with signal and ADC, you will see inconsitant waveforms from mulitple capture. becuase the starting phase of I/Q SIN/COS signals are different from time to time. 

    the device is complex. I am sure you can use it well after more testing. Thanks!

  • 0 in reply to Xiaochen (Sean)Xu
    Intellectual 290 points

    thanks for your answer sir!, 

    firstable, I reduce the ADCCLOCK to 20MSPS in order to work better with low frequency, that is 40KHz, following your explanation I have aprox 10ms of PRF, trigger signal, so 20Mx10m = 200K points, that can adjust in the HSDC PRO GUI/data capture options/capture option and set the #samples acording to my election? for example 450K samples to capture two triggers?, 

    that is my doubt since the beginning beacuase I have several emisions and several triggers to send to the evals to receive each echoes but i am only capable to receive the first data produced by only the first trigger signal.

    my adcclok, trigger and signal are syncs

  • 0 in reply to Mateo Recalde
    TI__Expert 6040 points

    The TSW GUI is designed to respond the first trig. Then capture N points as user set. 

    Let us say, 200K point per trig, you set as 655K in the TSW capture. you will capture 3 trig events. I assume you will see 0x2727 codes three times in the captured data. this is the most visiable sign for demodulated data. 

    Thanks!

  • 0 in reply to Xiaochen (Sean)Xu
    Intellectual 290 points

    thank you very much sir!, It is very helpful the direct answer regarding the trigger, now I can see for example two events for the moment because the analysis window is up to  524288.

    about the 0x2727 (is not 0x2772?) is that the sync word? I read this post(https://e2e.ti.com/support/data-converters/f/73/t/530333?Is-it-possible-to-configure-the-demodulator-in-AFE5809-to-pass-through-ADC-data-to-LVDS-) and I will follow those steps in order to get the sync signal(sync word), after that I am available to enable the demod stage?

  • 0 in reply to Mateo Recalde
    TI__Expert 6040 points

    yes, should be 0x2772. typo:)

    Thanks!

  • 0 in reply to Xiaochen (Sean)Xu
    Intellectual 290 points

    don't worry!, one more question regarding to the demod stage, what is the specific job of this two options, MODULATE_BYPASS and DIG_DEMODULATOR(DISABLED/ENABLE)?
    -how should be the setup about those?
    DIG_DEMODULATOR(ENABLED)
    MODULATE_BYPASS checked
    for demod stage? or how?
    -what is their priority regarding to the demodulation procedures, please if you can clarify this for me

    Regards

  • 0 in reply to Mateo Recalde
    TI__Expert 6040 points

    DIG_DEMODULATOR will shut down everything in demod digital , include MODULATE_BYPASS

    DIG_DEMODULATOR(ENABLED)
    MODULATE_BYPASS checked

    means you only doing deciatmion. 

    please refer to the datasheet for more details on the register settings. 

    Thanks!

  • 0 in reply to Xiaochen (Sean)Xu
    Intellectual 290 points

    Thanks you so much for helping me sir!,