Capturing Audio

Can anyone recommend a chip that I can use to capture simple
audio (44 Khz, 16-bit one channel for example). This is for
a hobby project where I would like to sample audio from a
microphone and send it to a PC through either USB or RS232.

I'm a complete newbie and I'm not sure where to start. Maybe
someone can point me to an existing project or a magazine
article that describes such a thing?

 S.

Stefan Arentz <stefan.arentz@gmail.com> wrote:

> Can anyone recommend a chip that I can use to capture simple
> audio (44 Khz, 16-bit one channel for example). This is for
> a hobby project where I would like to sample audio from a
> microphone and send it to a PC through either USB or RS232.

You can forget 44khz 16 bit audio going over RS232....

Is there a particular reason to design something yourself rather than 
using one of the existing audio/USB converters? (for the sake of doing it 
yourself/learning perhaps?)

If so, you might want to start with something simpler.

Good resources: www.embedded.com , www.circuitcellar.com 

--buddy

Buddy Smith <buddy@tpac.gatech.edu> writes:

> Stefan Arentz <stefan.arentz@gmail.com> wrote:
> 
> > Can anyone recommend a chip that I can use to capture simple
> > audio (44 Khz, 16-bit one channel for example). This is for
> > a hobby project where I would like to sample audio from a
> > microphone and send it to a PC through either USB or RS232.
> 
> You can forget 44khz 16 bit audio going over RS232....

I realized that after I sent that message :)

The audio quality is actually not very important. As long as speech will
be recognizable it will be fine.

> Is there a particular reason to design something yourself rather than 
> using one of the existing audio/USB converters? (for the sake of doing it 
> yourself/learning perhaps?)

Mostly learning and experimenting.

> If so, you might want to start with something simpler.

Grr :-)

 S.

"Stefan Arentz" <stefan.arentz@gmail.com> wrote in message
news:87u0t9thvj.fsf@keizer.soze.com...
> Buddy Smith <buddy@tpac.gatech.edu> writes:
>
> > Stefan Arentz <stefan.arentz@gmail.com> wrote:
> >
> > > Can anyone recommend a chip that I can use to capture simple
> > > audio (44 Khz, 16-bit one channel for example). This is for
> > > a hobby project where I would like to sample audio from a
> > > microphone and send it to a PC through either USB or RS232.
> >
> > You can forget 44khz 16 bit audio going over RS232....
>
> I realized that after I sent that message :)
>
> The audio quality is actually not very important. As long as speech will
> be recognizable it will be fine.
>
> > Is there a particular reason to design something yourself rather than
> > using one of the existing audio/USB converters? (for the sake of doing
it
> > yourself/learning perhaps?)
>
> Mostly learning and experimenting.
>
> > If so, you might want to start with something simpler.
>
> Grr :-)

What you could do, is use a parallel 8 bit ADC and a FTDI FT245 for the USB
interface. You can program the USB chip (there are ready made modules that
contain everything) to capture 8 bits of data at a certain rate. To the PC
it appears as another COM port. See www.ftdichip.com.

You also would need to construct an antialiasing filter before the ADC
input.

Jeroen

Stefan Arentz wrote:
> Can anyone recommend a chip that I can use to capture simple
> audio (44 Khz, 16-bit one channel for example). This is for
> a hobby project where I would like to sample audio from a
> microphone and send it to a PC through either USB or RS232.
> 
> I'm a complete newbie and I'm not sure where to start. Maybe
> someone can point me to an existing project or a magazine
> article that describes such a thing?
> 
>  S.

I've started messing with TI's PCM1801. It's two channel, goes down to 
4kHz, and is very affordable. Interface is serial clocked, so you'll 
need some glue before poking it into the PC. I guess you've considered 
using the microphone input? Most motherboards have them nowadays.

Regards,
Mike.

-- 
Mike Page BEng(Hons) MIEE           www.eclectic-web.co.uk
Quiet! Tony's battling the forces of conservatism, whoever we are.

"Jeroen" <jayjay.1974@xs4all.nl> wrote in message
news:4162cce1$0$78753$e4fe514c@news.xs4all.nl...
>
> "Stefan Arentz" <stefan.arentz@gmail.com> wrote in message
> news:87u0t9thvj.fsf@keizer.soze.com...
> > Buddy Smith <buddy@tpac.gatech.edu> writes:
> >
> > > Stefan Arentz <stefan.arentz@gmail.com> wrote:
> > >
> > > > Can anyone recommend a chip that I can use to capture simple
> > > > audio (44 Khz, 16-bit one channel for example). This is for
> > > > a hobby project where I would like to sample audio from a
> > > > microphone and send it to a PC through either USB or RS232.
> > >
> > > You can forget 44khz 16 bit audio going over RS232....
> >
> > I realized that after I sent that message :)
> >
> > The audio quality is actually not very important. As long as speech will
> > be recognizable it will be fine.
> >
> > > Is there a particular reason to design something yourself rather than
> > > using one of the existing audio/USB converters? (for the sake of doing
> it
> > > yourself/learning perhaps?)
> >
> > Mostly learning and experimenting.
> >
> > > If so, you might want to start with something simpler.
> >
> > Grr :-)
>
> What you could do, is use a parallel 8 bit ADC and a FTDI FT245 for the
USB
> interface. You can program the USB chip (there are ready made modules that
> contain everything) to capture 8 bits of data at a certain rate. To the PC
> it appears as another COM port. See www.ftdichip.com.
>
> You also would need to construct an antialiasing filter before the ADC
> input.
>
> Jeroen

Another possibility is to sample it at 8 KHz, 14-bit per sample. Then use
G.711 encoder (mju/A law) to get it down to 8 bits per sample. On the
receive side use G.711 decoder. That'll be phone line quality and it'll fit
RS232 bandwith (8000 bytes/second * 8 bits/byte = 64000 bits/second, whearas
all normal UARTs support at least 115200 bits/second; if you tune it to
230400, you can have better quality or stereo :).

Alex

"Stefan Arentz" <stefan.arentz@gmail.com> wrote in message
news:87pt3x32ud.fsf@keizer.soze.com...
>
> Can anyone recommend a chip that I can use to capture simple
> audio (44 Khz, 16-bit one channel for example). This is for
> a hobby project where I would like to sample audio from a
> microphone and send it to a PC through either USB or RS232.
>
> I'm a complete newbie and I'm not sure where to start. Maybe
> someone can point me to an existing project or a magazine
> article that describes such a thing?

Elektor magazine has publised a USB soundcard AFAIK

Wim