Sound recording methods?

Morgan

Hi all,

· I have built a·couple BS2 projects in the past and·am now trying to build a sound (voice, mainly)·recording device, which I've not worked with before.· I searched through the forum and found a lot of information on voice synthesis & sound output, but not much on recording·input from a microphone.· Basically, what I am trying to come up with is a way to constantly (24/7) record sound to RAM, with new audio·data being written·and·old audio·data purged (maybe a 4 minute buffer or so), until a sensor is triggered.· When the sensor is triggered, the audio in RAM will be transferred to ROM for storage, then the·process starts over again.· The "sound bytes" sent to ROM would be approximately 1-2 minutes in length.· I would like to be able to retrieve the ROM recordings in a standard format, such as .wav, but could·maybe settle for just being able to play the files back directly (would definitely prefer creating PC savable files).

· Has anyone done something like this before (or have any ideas)?· I need to fit the device into a fairly small package, so I'd rather not have to·use a big "fully loaded" component that has extra features I don't need to use in this application.· Would it be possible to do this somehow with simple·discrete components,·such as·an A/D converter connected to memory, microphone, BS2, and misc. components?· Or does anyone know of an all-in-one·IC that may be up to the task?

Thanks for reading my post and in advance for any assistance you can provide!

Morgan

Jon Williams

That's a lot to ask -- your sample rate will affect the amount of RAM required. At CD quality you'd need 44.1K bytes for one second of sound (mono) -- multiply that by 240 (four minutes) and that's a huge chunk of RAM. Even if you get down to an 8K sample rate, you're looking at almost 2 megs of RAM.

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Jon Williams
Applications Engineer, Parallax