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Algo for rms computation?

ggabe

I’m entertaining a true rms computation on MSPM0G3507 for the 10Hz…100KHz range. 

The MCU is limited to 32K RAM, so I’d change the sampling frequency if I can determine the signal is periodic and in the lower frequency range.

Is there any algorithm that aims capture N periods of a periodic signal? 

Should I be better of by going into frequency domain with a proper window function, and possibly trying multiple sampling rates to choose the proper range?

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  • Interesting chip!

    image

    I didn't see the cycle counts for the math co-processor but it looks interesting.

  • in reply to scottiebabe

    If the TI part piqued your interest then there is STM32G431. It has single precision float, CORDIC and FMATH accelerators, imo better than IT's offering. 

    Cordic features

    • 24-bit CORDIC rotation engine

    • Circular and Hyperbolic modes

    • Rotation and Vectoring modes

    • Functions: Sine, Cosine, Sinh, Cosh, Atan, Atan2, Atanh, Modulus, Square root, Natural logarithm

    • Programmable precision up to 20-bit

    • Fast convergence: 4 bits per clock cycle

    • Supports 16-bit and 32-bit fixed point input and output formats

    • Low latency AHB slave interface

    • Results can be read as soon as ready without polling or interrupt

    • DMA read and write channels

    FMAC features

    • 16 x 16-bit multiplier

    • 24+2-bit accumulator with addition and subtraction

    • 16-bit input and output data

    • 256 x 16-bit local memory

    • Up to three areas can be defined in memory for data buffers (two input, one output), defined by programmable base address pointers and associated size registers

    • Input and output sample buffers can be circular

    • Buffer “watermark” feature reduces overhead in interrupt mode

    • Filter functions: FIR, IIR (direct form 1)

    • AHB slave interface

    • DMA read and write data channels

  • in reply to ggabe

    What I liked about the TI part is that it's so cheap !

    I have  a project for a client in mind where it's a prefect fit (and the cheapness matters).

    I've ordered a couple of the eval boards.

    MK

  • in reply to michaelkellett

    True! And it has one extra ENOB on the ADC specs, as TI boldly points out.

    What I also like about the TI EVB is the SMPS is implemented with software loop control. Allows exact power consumption measurement.

  • in reply to ggabe

    Your bandwidth isn't too far off audio

    image

    I wonder what some of the spare no expense sound level meters do, presumably all of the analysis is done in the digital domain, with perhaps a programable LNA up front...

    image

    Wish the teardown photos were higher resolution, lol 

    image

    https://fccid.io/2ASFB-2245-1/Internal-Photos/Internal-Photos-4337264 

    Oh and also a neat chip!

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