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MSP430FR5988: FFT And high rate ADC

HY yang
Expert 1960 points
Part Number: MSP430FR5988

We need to analyze the spectrum and phase of 1kHz periodic signal. We need to use ADC to sample the 1kHz signal, and then perform FFT operation. Is there a suitable MCU recommended? The price shall be less than 2USD.

  • 0
    Guru 88460 points

    I encourage you to read over Application Report SLAA698B. While this report is focused on the LEA (not present in the FR5988) it contains some other useful items.

    Table 3 row 2 indicates the clocks / time for a 256-point complex FFT without the LEA, at  106k clocks / 13.3 msec at 8MHz. With a 2ksps ADC, 256 samples is 128 msec, a 10:1 margin, so this seems feasible. This is 16-bit fixed-point; a floating-point FFT is probably infeasible.

    Aside from the LEA, the FR5 series has (as far as I know) no particular DSP advantage over the FR2 series, so I would expect these numbers to (roughly) hold there. The FR2 series is where you'll find the $2 devices. TI's product selector is a resource here. Things to watch for:

    1) None of the FR2 series has DMA

    2) Only some of the FR2s have 12-bit ADCs (the rest are 10-bit or nonexistent).

    3) Be sure there's enough SRAM to hold your samples (some of the FR2s are pretty small).

    4) Only some FR2s have a hardware multiplier (MPY32)

    [Edit: forgot the MPY32]

  • 0
    Guru 18795 points

    How often do you do this? What resolution is required? What sample rate?

    In any case, this is the sort of analysis you pay engineers to do. Hire one.

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