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PICList Thread
'[PIC] Need advise on sound recording'
2009\06\04@035327 by Harry H. Arends

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Hello Group,

I need some advice on the following.
We want to make a recording device that records sounds for up to 30
mins and stores that on a MCC/SD card.
It should be in the .WAV file format on that card so it can be
prosessed on a Laptop computer.

Are there allready project amoung the list users and are there any
pitfals using a PIC.

Regards

Harry

2009\06\04@122228 by Herbert Graf

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On Thu, 2009-06-04 at 09:54 +0200, Harry H. Arends wrote:
> Hello Group,
>
> I need some advice on the following.
> We want to make a recording device that records sounds for up to 30
> mins and stores that on a MCC/SD card.
> It should be in the .WAV file format on that card so it can be
> prosessed on a Laptop computer.
>
> Are there allready project amoung the list users and are there any
> pitfals using a PIC.

I'm sure there are, but to be honest, unless this is for a learning
experience I wouldn't bother. There are and have been many devices sold
for many years that do this. I have a 5 year old MP3 player with an SD
card slot that does this. No point re-inventing the wheel unless that's
what you're interested in doing.

TTYL

2009\06\05@000430 by Carey Fisher

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Working on a similar special purpose project...record audio using a PIC A/D
(w/filter) and write it out to RAM.  After delay, retrieve data from RAM and
send it out PIC Port w/filtering.  Need <10 sec so using SRAM.  Lots of
programmable options.
Chip suggestions would be helpful.  Now planning to use PIC18F452 or 4520.
Is it worth implementing AGC to avoid overloading the PIC A./D? Firware
filter of external OP-AMP with Digital Pot?

On Thu, Jun 4, 2009 at 12:22 PM, Herbert Graf <spam_OUThkgrafTakeThisOuTspamgmail.com> wrote:

{Quote hidden}

> -

2009\06\05@090149 by Gerhard Fiedler

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Carey Fisher wrote:

> Is it worth implementing AGC to avoid overloading the PIC A./D?

Probably it is. Uncompressed, raw audio can have a pretty wide amplitude
range. And human perception is closer to logarithmic than to linear --
but the ADC works linearly. So some degree of compression probably
helps.

> Firware filter of external OP-AMP with Digital Pot?

That would work. There are also pretty simple hardware solutions
(basically the same: low-pass into a VCG stage).

Gerhard

2009\06\05@092514 by olin piclist

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Gerhard Fiedler wrote:
>> Firware filter of external OP-AMP with Digital Pot?
>
> That would work. There are also pretty simple hardware solutions
> (basically the same: low-pass into a VCG stage).

You can also run a few different fixed gains into multiple A/D inputs.

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2009\06\05@134031 by Alan B. Pearce

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> Is it worth implementing AGC to avoid overloading the PIC A./D?

Microchip have just announced some variable gain code for DSPics. I haven't
looked at it at all, but it sounded like it would do this when set up
properly.

2009\06\05@161744 by Carey Fisher

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Thanks everyone!  I'll let you know how it turns out.Carey

On Fri, Jun 5, 2009 at 1:39 PM, Alan B. Pearce <.....Alan.B.PearceKILLspamspam@spam@stfc.ac.uk>wrote:

> > Is it worth implementing AGC to avoid overloading the PIC A./D?
>
> Microchip have just announced some variable gain code for DSPics. I haven't
> looked at it at all, but it sounded like it would do this when set up
> properly.
>
> -

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