One thing to watch for is that the hardware MUST cutoff above 4khz to
avoid aliasing. Or else you sample at, say, 128KHz and filter with an IIR,
but this may not be achievable with a PIC.

I would be very interested to know if your XOR encoding trick really
works, I'm no wavehead but it seems like you are pushing information
out-of-band, for example one sample XOR's into 00 and the next into FF,
but the radio won't go from 00 to FF in 125 uS (call it slew rate, call it
bandpass). Not to mention the problem of syncing the receive with the
send.

You might try posing the question to usenet comp.dsp and see what those
guys have to say (for me, it's usually something like "What are you,
insane?" followed by a bunch of really excellent ideas and comments which
you must then downconvert into embedded reality :).

Rich

On Thu, 6 Jan 2000, Wesley Moore wrote:

> Date: Thu, 6 Jan 2000 17:26:10 +1100
> From: Wesley Moore <wmoore@CS.RMIT.EDU.AU>
> Reply-To: pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
> To: PICLIST@MITVMA.MIT.EDU
> Subject: ADC and voice sampling
>
> Hello all,
> I am interested in making a PIC based project in which I need to encrypt
> voice. The voice is encrypted for transmission using a UHF radio.
> Basically the person speaks into the microphone normally, the PIC samples
> the analog data from the microphone at a minimum rate of 8kHz, XOR's it
> with a preset 'key' and converts it back to analog for transmission. At
> the other end the opposite is done. My question is does you run of the
> mill ADC0831 8-bit ADC have what it takes to sample a voice signal?