From: "Sir Charles W. Shults III"
Subject: Re: How to implement an EEPROM for audio
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Tue, 17 Sep 2002 00:37:34 GMT
NNTP-Posting-Date: Mon, 16 Sep 2002 20:37:34 EDT
Organization: RoadRunner - Central Florida
Well, let's look at some numbers.
For CD quality audio, there are 44,100 samples per second per channel.
Let's call it 90Kbytes per second to get that. There are compression schemes
for getting better storage density bet we will skip that for now.
So, 20 tracks, 60 seconds, 90Kbytes- 108,000 Kbytes of flash storage to do
this. Or, in the parlance, about 100 megabytes. So a simple, brute-force
approach leads to you buying a 100 megabyte flash RAM unit and building up the
circuitry to run it- a processor, flash memory interface, input processing to
store the data (A to D conversion, two channels), and output circuitry (D to A
converters, 2 channels, audio amps, etc.)
For a simple sounding device, it quickly becomes a complex, rather expensive
project. But fun, of course.
Now, using a coding scheme (like an audio codec- they are available as
software or as hardware) you can compress this data considerably. You may cut
the storage down to 10 megabytes or so by using a good shareware ripper/codec
package, but you would want to run this on a fast PC- only to store the tracks
Playback can be fast and easy. The scheme can be exactly the same as MP3
and it can be very compact. In fact, they sell MP3 players, all ready to use.
The bottom line is-
a) buy a small MP3 player
b) get a good ripper program and MP3 compress your audio tracks on a PC or
c) program your OOPic or other small processor to control the audio playback
from the MP3 unit (which you pretty much have worked out)
d) the entire package will be under $100, done and nicely packaged
By writing your control tracks and audio tracks as you already do, you end
up with a system that looks just like a tape or CD system. You can determine
what your trigger conditions are, as with your existing system. Even Radio
Shack carries small MP3 players. I don't know how much capacity they have, but
they are cheap.
If it has a serial input or remote input, then you have it whipped. Even if
it doesn't, you can very easily run fine wiring from the contact points and use
your OOPic to trigger the closures you need.
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip