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Date:	Sun, 6 May 2012 19:23:04 +0200
From:	Peter Stuge <peter AT stuge DOT se>
To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] 16 bit signed PCM .wav file into an EEPROM
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Rob Butts wrote:
> Microchip 8 bit microcontroller with six IO pins
..
> My dilemma:
> 1.  What is the best/easiest file type to convert the quack to.
> 2.  How to get the .wav file (or other file type) from my hard drive
> into the eeprom.
> 3.  What type of cheap DAC chip to use (not familiar with them at all).

Need much more information about requirements to give good advice.
How cost and power sensitive is the final solution? What volume will
you manufacture and how? Are you hand soldering or not? Are you
comfortable with very small surface mount pitches?

16-bit .wav is probably much too high quality for the target system,
and the file may also be in stereo so if you have just one speaker
you could possibly reduce the .wav file size by 75%. 64kbyte EEPROMs
are not so hard to find.

Then, you have to produce the output. I assume that all six IO pins
are not available for audio output. How many are available? Does the
micro have a USART which is available, or will you have to bitbang
everything? This may matter since especially some smaller PICs don't
go too high up on the MIPS scale.

For mp3 you could look at some of the numerous PIC+STA013 projects
documented on the internet. They also include various DACs.

For a more all-in-one solution you could replace the PIC completely
and go for a fully open compressed format such as Ogg Vorbis or FLAC,
using VS8053:

http://www.vlsi.fi/en/products/vs8053.html

Note that it is possible to add user code into the VS8053, and it
includes the DAC, so it is truly a single chip solution. It's of
course more expensive and power hungry than a PIC though.


//Peter

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