ditital voice

[Jeff]

Can anybody help me design a circuit that will digitize voice and
place the data into RAM, then read it and convert it back? The chips
from ISD won't work for my situation because there is no access to the
data. I want to be able to read the data in reverse to play the audio
backwards. I am going to have to use A/D and D/A converters and a PIC
microcontroller to do the job for me. My question is: Which is the
best A/D and D/A converters to use for a clear voice recording? What
should the sampling rate be? How many bits/resolution should I be
looking for? The PIC16F872 has a 10-bit A/D converter built in but I
am not well versed in Assembly Language and my BASIC compiler doesn't
support this function as far as I know. So, my thought is to build a
circuit around the PIC16F872 which will provide the address for the
RAM and sync pulse for the A/D converter. The converter will send
serial data to the RAM to store the recording. The PIC16F872 will
interpret which button is pushed by the user and access the RAM either
forwards or backwards (count up/ count down). Data will be sent to the
D/A converter and play the audio. Any suggestions?

Thanks.

 

[Kirk Shirley]

There are many PC based solutions to digitize and play your message
backwards.
Is there a reason you can't do this?
Kirk

 

[Jeff]

There are many PC based solutions to digitize and play your message
backwards.
Is there a reason you can't do this?
Kirk

My project must be stand-alone. It can't rely on a PC. It should be a
rather simple circuit. I'm just not sure if simply accessing the
digital data in reverse will convert the original audio to play
backwards. There are hundreds of A/D converters out there. If anybody
has experience using them to digitize audio, I just need to know which
one to choose.

 

[nemo]

Do a Google search on the phrase "analogue to digital converter" It will
point you towards other chips and searching on the phrase, "analogue to
digital conversion" might turn up the sort of info you're after.

The ones I know about like the ZN 435 which can work both ways round BTW but
blows up at the slightest hint of static, are rather obsolete nowadays.

Hope this helps,

Nemo