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EK-TM4C1294XL: CMSIS DSP Library for TM4C129

Sumit Mourya
Expert 1790 points
Part Number: EK-TM4C1294XL

Hello All,

I'am trying to use CMSIS DSP Library with TM4C1294XL Launchpad. I'am implementing the low pass filter of the library using arm_fir_f32 function. 

In the Fir example for the library it is written

* Note that the filter is symmetric (a property of linear phase FIR filters)
* and the point of symmetry is sample 14. Thus the filter will have a delay of
* 14 samples for all frequencies.

That means the filter will have a delay of (N-1) samples i.e. (NUM_TAPS -1)/2 in its output

Now this property does not gives a real time continuous  filter output signal which can be plotted further.

How to remove this delay in the output signal?

kindly suggest a solution for the problem

  • 0
    Guru 27665 points
    Design a circuit to sample the future waveform instead. Or perhaps simpler, don't use a symmetric FIR.

    A general DSP guide that contains a reasonable discussion of filters.

    www.analog.com/.../scientist_engineers_guide.html

    Robert
  • 0 in reply to Robert Adsett
    Guru 117855 points

    *** LIKE ***

    To your "well thought TAG" (it also warrants a "LIKE") - the clause, "become a skilled tech investigator" may deserve consideration.    

    Regarding the "TAG" entry - is not vendor's: "Forced, MCU IDs inclusion" - too often an "ILL CONSIDERED" LIMITATION!    Robert's advice here, "Is surely NOT bound to any SINGLE vendor MCU" - thus forcing the post's Tag to MCU_X (may) preclude this valuable posting from being found by those employing a "different, vendor supplied, MCU!"    Had that fact been noted - even considered?    (appears similar to the most unfortunate, highly troubling: "Banning of LIKE" - justified via grade-school logic!      (a slow grade school - at that!)

    Most always more appropriate - "broad based investigations" provide:

    • added detail
    • competing viewpoints
    • limitations of the approach (possible suggestions of "other" methods")   [illustrated by you - right here - "Don't use a symmetric FIR!"]

    Poster "has" made good effort - yet "broadening his investigatory base" (far beyond this MCU forum) will prove his best "roadmap to success!"   (R.A. may not (always) be at "beck & call!")