Hot!FFTComplex32bIP on dsPIC33(CK): examples or documentation?

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u741
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2019/02/24 15:17:52 (permalink)
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FFTComplex32bIP on dsPIC33(CK): examples or documentation?

Hello all,
 
I got the 16-bit complex FFT (using FFTComplexIP(), and TwidFactorInit(), BitReverseComplex(), SquareMagnitudeCplx() ) successfully running on a dsPIC33CK device, using the updated library provided by Microchip support, and the excellent "application note" TB3141 of 2015.
 
I need more dynamic range in the magnitude for smaller-magnitude signals (which I confirmed in MATLAB I could get by 32bit, using the same, 12bit input data from the ADC), so I want to try FFTComplex32bIP(). The 33CK devices should have enough power even for 32bit, since a 512-point 16bit FFT takes less than 0.5 ms.
 
There are several very old threads on this topic, all commenting: the lack of source code examples, lack of documentation, some fundamental uncertainty whether FFTComplex32bIP() only works for 1024 array size despite having arguments allowing variable size, uncertain data composition of complex (long) input vectors, unknown twiddle factor calculation, unknown bit-reverse calculation, etc. No solutions are in the forum to these questions.
 
By now, has anyone a complex 32bit FFT successfully running on any dsPIC33? could you share your source code? or is there any other documentation on 32bit complex FFT on dsPIC available by now?
 
thank you.
post edited by u741 - 2019/02/24 15:19:00
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    u741
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    Re: FFTComplex32bIP on dsPIC33(CK): examples or documentation? 2019/02/26 02:23:17 (permalink)
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    seems not much people doing signal processing using DSP functions ... perhaps DSP functionality is obsolete?
     
    perhaps everyone is using the cheap and low-power 32-bit microprocessors with 32-bit float, which are with software-coded FFT/IIR/FIR as fast (and much more accurate) as a 16-bit DSP core with hardware implementation?
     
    or what are the applications out in the real world for the DSP functionality of the dsPIC MCUs? are the MAC-units used for something else nowadays than classical time-domain signal processing?
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    firmwareNovice
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    Re: FFTComplex32bIP on dsPIC33(CK): examples or documentation? 2019/03/13 11:19:00 (permalink)
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    Hi u741,
     
    As it turns out, I actually am looking to use the DSP libraries for my application (need to compute cross-correlation on two 1000-element vectors, hoping to use an FFT-based algorithm for that).
     
    To do this, I'm using ADC data sampled from a dsPIC33CK256MP506 device.
     
    Question: 
    Where/how do I get access to these DSP libraries? The alternative is to write my own software functions, which I've done (but are way too slow for my application).
     
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    u741
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    Re: FFTComplex32bIP on dsPIC33(CK): examples or documentation? 2019/04/16 22:40:02 (permalink)
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    I received working DSP libraries for the dsPIC33C devices, after filing a support ticket.
     
    I confirmed that FFT (complex, 16bit), IIR and FIR functions as well as auxiliary functions around these functions work as expected, and also very fast.
     
    I might at some point also be interested in testing 32bit realFFT, but I have no need for that now
     
    It's 500 kB; if you tell me how I can send you the library, I will do so, and then you don't have to bother Microchip with another support ticket which will take some time to resolve.
     
    It could be that a newer version (I'm using XC-16 v1.35) already has the updated libraries included, which also work for the Cx devices.
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