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.
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:
--buddy
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.
Mostly learning and experimenting.
Grr :-)
S.
it
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
You also would need to construct an antialiasing filter before the ADC input.
Jeroen
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.
USB
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
Elektor magazine has publised a USB soundcard AFAIK
Wim
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