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ADS5294: Oversampling, 12 tap filter

Gerhard Stresing
Prodigy 10 points
Part Number: ADS5294
Other Parts Discussed in Thread: ADS5292

Hi, the datasheet of the ADS5294 is describing a key feature "Oversampling to Minimize Harmonic Interference" and in figure 55 is a 12-tap filter shown. I have not found any documentation on either of these topics. In my application I want to do a moving average for the current and the last few values. This isn't possible with the 24-tap and 23-tap filters, because they are symmetric, am I right? Is it possible to achieve a moving average like I described and when yes, how?

www.ti.com/.../ads5294.pdf

  • 0
    TI__Genius 12025 points

    Hi,

    Thanks for using ADS5294 device.

    For your concern about the device's symmetrical coefficients of the filter,

    you may also refer to ADS5292 Data sheet page 39 to page 42 for more details

    which is very similar to ADS5294's decimation filters.

    Hope this can help for your application.

    Best regards,

    Chen

  • 0 in reply to Chen Kung
    Prodigy 10 points

    Hi Chen,

    thanks for your reply. I looked into this datasheet https://www.ti.com/lit/ds/symlink/ads5292.pdf and didn't find any difference to the ADS5294 datasheet regarding the decimation filters. So there are no addtional informtion.

  • 0 in reply to Gerhard Stresing
    TI__Genius 12025 points

    Hi,

    Yes, that is also showing you how ADS5294 is working in details.

    For your special application, yes, you can use ADS5294 device Tap filter

    to work on your moving average function.

    Could you please let me know whether the following example is correct or not?

    Assume you want to do this kind of moving average shown as:

    y(3) = 1/3 * (x(3) + x(2) + x(1))

    assuming y3 is Moving Average result

    x3, x2, x1 are your current and last few values

    (of course, you can continue to do more x4, x5, ... and so on.)

    If this is what you want to run on ADS5294 device,

    then I can explain more to you.

    Thank you!

  • 0 in reply to Chen Kung
    Prodigy 10 points

    Yes, this is exactly what I want to do.

  • +1 in reply to Gerhard Stresing
    TI__Genius 12025 points

    Hi,

    How are you?

    Here is one example to show you how to modify and setting the on-chip register.

    and also here are some assumptions for explanation (later you and modify and add more as you need.)

    Thank you!

    1. Assume we only need to use x3, x2 and x1 captured data.

    2. Assume we only apply Channel 1 right now.

    3. Assume we are using 23-tap FIR <ODD_TAPn>=1 is implemented for this case.

    4. Please look at the ADS5294 Data Sheet Page 53,

        and you can see the equation (3).

        you can set h0=h1=...=h9=0 and also set h10=h11=(2^11)/3.

        This will delay by 13 captured samples before you can star to read the y result.

    5. You can see the 1st captured valid y result as: Please see the data sheet page 53.

        y(13)=(1/2^11) (0+0+...+0+h10*x(3)+h11*x(2)+h10*x(1)+0+0+...0)

        Please set h10=h11=(2^11/3)

    6. And then you can continue and see

        y(14)=(1/2^11) (h10*x(4)+h11*x(3)+h10*x(2))

        y(15)=(1/2^11) (h10*x(5)+h11*x(4)+h10*x(3))

        ... and so on

        Note: please set h10=h11=(2^11/3)

    7. The please setup the control register

        Please see Data Sheet page 55 Table 17

        Please use Bypass decimation option

    8. Also Set the register as

        (Assume using Channel 1 only in this case)

        (Please see the Data Sheet page 55)

        Hex 5A address, h0 data set to = 0

        Hex 5B address, h1 data set to = 0

        Hex 5C address, h2 data set to = 0

        Hex 5D address, h3 data set to = 0

        Hex 5E address, h4 data set to = 0

        Hex 5F address, h5 data set to = 0

        Hex 60 address, h6 data set to = 0

        Hex 61 address, h7 data set to = 0

        Hex 62 address, h8 data set to = 0

        Hex 63 address, h9 data set to = 0

        Hex 64 address, h10 data set to = 2^11/3

        Hex 65 address, h11 data set to = 2^11/3

    9. Of course, this is just one example.

        Please continue to change any setup as you need.

    Thank you for using ADS5294 device.

  • 0 in reply to Chen Kung
    Prodigy 10 points

    Thank you very much. I got the idea now!