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TIDA-010231: FFT execution time

Part Number: TIDA-010231

Hi champs,

I have read the Design Guide of TIDA-010231 and I cannot find the data of FFT execution time. In this design it use 1024 sampling points FFT and how long or how many cycles it will cost? Could you please help to confirm it? Thanks!

Best,

Julia

  • Hi Julia,

    In the latest version of our test software we use FPU for the FFT calculation. With this implementation the whole arc detecting algorithms need about 55 MIPS in worst case for one channel. 
    The amount of required MIPS depends on the configurable parameters of the algorithm, like how wide the spectrum for arc detection is selected. We are working further on improving this.

    Best regards,

    Andreas

  • Hi Andreas,

    Thanks for your information. I want to double check with you how long does 55 MIPS correspond to? When MCU is F280049, if this algorithm only use CPU without CLA, total MIPS will be 100MIPS and 55MIPS will cost 0.55s? If this algorithm use CPU and CLA, total MIPS will be 200MIPS and 55MIPS will cost 0.275s?

    I don't know if my understanding is correct. Thanks!

    Best,

    Julia

  • HI Julia,

    Let me clarify that. My first response was not that precise.
    If we run our algorithm continuously we use 55 MIPS out of the 100 MIPS the F280049C CPU provides.
    We do not use CLA at the moment. So we basically need 55% of the processing power of the F280049C to run 1 Channel of arc detection continuously.

    Now we can break this down. We use 250 kHz of sampling frequency and do a 1024 point FFT for the algorithm. This means we execute the algorithm every 4.1 ms. With 55% MIPS used this means one round of the algorithm takes roughly 2.3 ms. Which would be 230000 cycles at 100 MHz clock frequency.
    I do not have the exact numbers at hand. but this is good estimation. 

    I hope this helps.

    Best regards,

    Andreas

  • Hi Andreas,

    Thanks for your clarification, that is clear.

    Best,

    Julia