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How to use the mic on PropBOE — Parallax Forums

How to use the mic on PropBOE

AwesomeCronkAwesomeCronk Posts: 1,055
in Propeller 1
I have an interesting project involving frequency detection and isolation(audible).

I need a driver of spin/pasm type. I also need info.

Comments

  • Mike GreenMike Green Posts: 23,101
    There are several sample programs in the OBEX under Speech/Sound like this. Also look at the application note on sigma-delta analog to digital conversion (AN008) which is used for the microphone.
    pdf
    pdf
    AN008-SigmaDeltaADC-v1.0_0.pdf
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  • AwesomeCronkAwesomeCronk Posts: 1,055
    Sorry for the late follow-up. Can this object detect and isolate multiple frequencies and log their intensity to a memory address?
  • Mike GreenMike Green Posts: 23,101
    It sounds like you want much more than just a driver. It sounds like you want a Fourier transform sort of program. The OBEX has one that could be used as a model, but you'd need to understand the techniques and German as well (leaves me out). Maybe someone else can recommend a reference with examples, maybe in C.
  • AwesomeCronkAwesomeCronk Posts: 1,055
    My idea is a VGA-based audio visualizer reading off of the mic.
  • kwinnkwinn Posts: 8,697
    AwesomeCronk wrote: »
    My idea is a VGA-based audio visualizer reading off of the mic.

    If you mean producing a real time Fourier transform display on VGA using the P1 (or even P2) I think you will find that it does not have the number crunching horsepower to accomplish the task. Even using the FFT would most likely be more than it can do.
  • AwesomeCronkAwesomeCronk Posts: 1,055
    So, could the prop precalculate the transform from a .wav file, then play the .wav while simultaneously displaying the transform by reading it from memory?
  • AwesomeCronkAwesomeCronk Posts: 1,055
    I would only want to chunk frequencies in groups of around 300Hz to 400Hz difference. This way I could capture the audible spectrum(20Hz-20kHz) with only 50 bars on screen
  • kwinnkwinn Posts: 8,697
    edited 2019-09-06 18:03
    AwesomeCronk wrote: »
    I would only want to chunk frequencies in groups of around 300Hz to 400Hz difference. This way I could capture the audible spectrum(20Hz-20kHz) with only 50 bars on screen

    That might be possible if you use filters to separate the frequencies and ADC's to measure the power of each band. That requires a lot of filter and ADC circuitry for 50 channels though. Typical high end HiFi units use fewer bands with different band widths for each range.

    EDIT - I wonder if there is a reasonably priced DSP available to do this.
  • AwesomeCronkAwesomeCronk Posts: 1,055
    So, chock it down at 25ish channels, make some adc/frequency filters, connect them to the prop, display them?
  • kwinnkwinn Posts: 8,697
    AwesomeCronk wrote: »
    So, chock it down at 25ish channels, make some adc/frequency filters, connect them to the prop, display them?

    Yes, something like that would work, however since many adc's come in 8 channel versions using a multiple of 8 channels might be a good idea. Perhaps a modular design using a small board with 8 filters and an 8 channel adc. That way you could add additional boards to increase the number of channels and use a dedicated cog for each board if required.
  • AwesomeCronkAwesomeCronk Posts: 1,055
    Yes, then we could have as many boards as pins.(as soon as the P2 is done, we need a 64io P1!)

    I have blank tht proto boards in my drawer, about 30x17 holes, 2.54mm spacing. Just need to source some adcs and some filters!
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