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A/D, D/A, & analog switches @audio freq's - your recommendations? — Parallax Forums

A/D, D/A, & analog switches @audio freq's - your recommendations?

CounterRotatingPropsCounterRotatingProps Posts: 1,132
edited 2009-06-20 01:26 in General Discussion
Posting here in the sandbox because the MC could be either a Prop, SX or both.
Intention = generic and wide-ranging·audio experimentation and signal generation

Min sample speed: uncompressed CD audio, mono, c.a. the 44.1 kHz 'standard'
Max s.s: 128 kbps
Prefer 16 bit, 24 could be better.

I am·aware that the Prop. is fully capable of serious audio work, but I'd like to off-load the conversions.

So the·parameters·are the typical Functionality vs. Price vs. Pins consumption.

1] Straight pin-4-pin, MC to A/D - D/A = Pros: speed, price. Cons: gobbles up pins.

2] I2C or SPI interface --- though·I understand the protocols generally, I don't·know if these are too expensive or difficult to control.

3] Even using the SX as a virtual A/D - D/A device wouldn't be out of the question, but am really looking for chips.


Any recommendations would be very much appreciated.
thanks,
- Howard

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Comments

  • LeonLeon Posts: 7,620
    edited 2009-06-14 22:23
    Codecs are usually used for audio instead of separate ADCs and DACs. They are available with I2S interfaces that connect directly to DSPs.

    Leon

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    Post Edited (Leon) : 6/14/2009 10:28:44 PM GMT
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-06-15 00:27
    Interesting - thanks, Leon - don't know why I hadn't thought of codecs ... ok, will do some research on them.

    Still would appreciate some suggestions for A/D & D/A stuff though as I'd like to 'roll my own' for a little practice again.

    Forgot to mention what's in the title ... am also looking for analog switches that are low-noise (when switching on/off that is) and inexpensive - for building a digitally controlled audio patch bay.

    cheers
    - Howard

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    Got Electrons?
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-06-18 15:35
    Leon, do you know of any sample code for using codecs for basic signal/function generation?

    thanks
    - H

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    and re-integrated into brand new marvels... We strongly encourage you
    to contact the provided information and recycle yourself always. "
  • LeonLeon Posts: 7,620
    edited 2009-06-18 17:44
    I have done that with an ADI DSP and codec, but it was a long time ago. The code was written in ADSP-21xx assembler.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-06-18 19:11
    That it needs a DSP attached makes sense - almost seems like I have the choice really between jumping the Parallax ship temporarily, using something like the ADI (I've always liked Analog Devices' components and support), or using TI's MSP430xxx --- or going back to rolling my own.

    Actually, I guess I shouldn't be so amazed at how many DSP+MC combo's there are. (Off topic: maybe the PropII will have some DSP onboard?)

    If you were wanting to build your own function generator (for example), what would you suggest. Yes, I know that's a really very broad specification... just the general drift...

    thanks again
    Cheers,
    Howard

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "This device contains recyclable materials, which can be re-decomposed

    and re-integrated into brand new marvels... We strongly encourage you
    to contact the provided information and recycle yourself always. "
  • LeonLeon Posts: 7,620
    edited 2009-06-19 13:09
    The MSP430 doesn't have any DSP functionality. The latest Microchip dsPICs are very good - 40 MIPS controllers with a DSP engine - and cheap.

    I've used an AVR with a software DDS as a function generator up to 200 kHz or so:

    www.geocities.com/leon_heller/minidds.html

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-06-19 19:43
    OK cool Leon --- I appreciate that you've put these things up on your site --- you've got quite a treasure trove of info there! - H

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  • LeonLeon Posts: 7,620
    edited 2009-06-19 19:49
    If I do anything that I think other people might find interesting I put it up on there.

    Leon

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Amateur radio callsign: G1HSM
    Suzuki SV1000S motorcycle
  • CounterRotatingPropsCounterRotatingProps Posts: 1,132
    edited 2009-06-20 01:26
    That extra effort pays off on many levels --- least of which is having to re-explain everything!

    I'm thinking of doing the same at some point, more along the line of learning notes. But it's time consuming...

    Posting your circuit board diagrams is helpful too. You "radio men" know a thing or two about RF - which certainly applies to the frequencies of controller and ancillary circuits these days. (E.g., the recent thread on capacitor placement.)

    - H

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