Audio to Digital - any sample around?

[flotulopex]

Hello,

I would like to use HOPE's RFM70 RF transceiver modules (http://www.hoperf.com/upload/rf/rfm70.pdf) as multiple headphone system - kind of audio "broadcasting" system for museum's visits or so (one sender, multiple receivers).

I have found quite a lot of (complicated) information all around internet, but no simple example.

Some sites propose to use TI LM4811 (http://www.ti.com/product/LM4811) or more complex chips such as DIX4192 (http://www.ti.com/lit/ds/symlink/dix4192.pdf) chips.

Did anyone make a project based on a PIC and that could share his information?

Thanks

[flotulopex]

Hello again,

Does nobody have done any audio to digital converter project up to now?

[Normnet]

Audio to digital is fairly simple.
Any PIC with an AD will convert the analog audio signals to digital (numerical value).
Simply take the reading at the preferred frequency (interval) for samples per second and select the AD whether 12 bit or 8 bit etc.

When received use a digital to analog converter to convert back.
I think some PIC's now have a basic built in DAC.
Add a pot for volume control, amp and a speaker.

I have done this successfully on a few designs.


Norm

[flotulopex]

Thanks Norm,

If you can share this, would you have a simple example of what you have made?

I would really appreciate a high level schema for the audio amp, for the mic and its input schema.

I think I can make it with the code ;-)

Did you do something like having two PICs connected via I2C; one is the "mic" and the other is the "loudspeaker"?

[Jerson]

First a clarification - why PIC? is it really needed?

To me, this looks like a classic radio broadcast problem. A straightforward solution (assuming the PIC is not needed) is to use a FM broadcast unit that you would connect to a TV/audio system and send the broadcast on the FM band.

My reply may be useless if there is a specific purpose to ADC the audio and then transmit via PIC. This however, IMHO, can be very under performing. The audio quality may be un-intelligible. Just off-the-cuff impressions.

[Normnet]

Jerson has a point.
Unless you are storing or reading from memory digitizing isn't required as the mic and speaker are both analog.
Also much more bandwith required for digital transfer.
Analog is roughly either amplitude modulation (AM) or frequency modulation (FM) which is just a signal where as digital requires many bits of information depending on the resolution whether it be 8 bit or 16 bit.

I you wish to digitize however I have a very complete example of reading audio posted at PIC iPod wav player (http://www.norm-online.net/PIC_iPod_wav_player.php)

I started with just a mic to a preamp to an amp to a speaker.
From their I digitized the pre amped mic signal on a PIC and then returned the signal to analog then to an amp and speaker with the same PIC.
Wired or wireless transfer of the digitized data between 2 PIC's would be next.

Audio is cool because you can hear the results.


Norm