Hi there,
I am looking for a recording device that would allow "non stop" digital audio recording. By non stop, I mean the device is always recording, and keeps around only the last 30 seconds of audio.
From a usage point of view, each time one presses the play button, the kit would play back the exact last 30 seconds of audio it's been recording til that very moment. There are kits out there that will digitally record 20 or 30 seconds, but this is not what I want - I need the device to use its memory as a circular buffer to always store the last 30 seconds (or 10 minutes) of audio.
I was wondering if it'd be easy to do something where you one would make the current memory pointer where the sound data must be written turn around and come back to the start of the buffer and the end is reached ?
Thanks for the input!

Denis

 

In principle, the simplest (solid state) way to do this is to have a variable-modulus address counter. You would read and then write the same address, and then advance the address counter. That way, your write pointer is right behind your read pointer. The variable modulus changes the delay time.
You will need DRAM (or a LOT of SRAM) to get the density to delay the audio by 10 minutes, and DRAM is a real pain to control compared to SRAM.
Perhaps an electromechanical storage solution would be simpler, like an endless tape loop, or your computer hard drive and some software (don't know if this is feasible).

__________________
Ron

 

Has to be all digital? How about using some ASDs (analog storing device) chips?

__________________
If is too complicated.....most of the times is the wrong way.

 

Ron, Harsil
Thanks for responding.
To answer your questions, I guess the recording doesn't have to be digital, but the device has to be portable, so no tape, and no pc. As for ASD, I guess it doesn't matter at first.
Still looking around on the web, and haven't found anything about such a device. :-(

 

I've seen that term used in a hoby revue (maybe wrong translation ). Anyway I was talking about some specialised chips like the ones from ISD1400 series:
http://www.jameco.com/Jameco/Products/ProdDS/107334.pdf
Maybe are some similar chips using volatile memory.I've seen that chip used in a kit. U could register a new msg few tens of thousands times. It's a long shot.
The advantage with that chip is that has almost everything in same pakage (ADC, memory, sampler etc.).
U'l need to use a uC to comand the chip. It has quite simple comands.
BTW....what's this project used for?

__________________
If is too complicated.....most of the times is the wrong way.