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Old 10th March 2009, 05:34 PM   #11
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yeah! Comes with I2s and an active forum @ avrfreaks.
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Old 10th March 2009, 06:35 PM   #12
Pano is online now Pano  United States
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Cool board - would like to see someone do an audio project with it.

Back to the topic. If you can't pull I2S off a laptop board, that's too bad. Would be a nice hack. The only easy way I know for USB to I2S is one of the BurrBrown USB DAC chips. Pretty simple and cheap. Can be USB bus powered. Limited to 32, 44.1, 48 Khz/ 16 bits.

Have you looked at any of the mini-itx boards? Maybe they can do what you want within budget?
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Old 14th March 2009, 01:26 AM   #13
njepitt is offline njepitt  United Kingdom
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Sorry about the long delay in replying. I am learning the hard way that old laptops may (and usually do) have unexpected things wrong with them....

At this point I have given up on the original laptop hack idea - apart from the problems that people explained above, I am finding that any laptop cheap enough to make the project attractive on cost grounds probably has too many problems to make it attractive in terms of time invested.

So here are a couple of remarks on replies from above.

Quote:
Originally posted by panomaniac
this one?

http://www.atmel.com/dyn/products/to...p?tool_id=4102
This looks really nice. I am trying to convince myself that food/clothes and so forth for the kids aren't really so important and I really *need* one of these....

I know there's a wiki, which I plan on reading in detail, but has anyone here bought one and used it as I would like to, as the first half of an ethernet DAC? Do you like it?

Quote:
Originally posted by panomaniac
Cool board - would like to see someone do an audio project with it.

Back to the topic. If you can't pull I2S off a laptop board, that's too bad. Would be a nice hack. The only easy way I know for USB to I2S is one of the BurrBrown USB DAC chips. Pretty simple and cheap. Can be USB bus powered. Limited to 32, 44.1, 48 Khz/ 16 bits.

Have you looked at any of the mini-itx boards? Maybe they can do what you want within budget?
I have built an Alien DAC kit, which uses one of the BB chips, and is fine as far as it goes (which is already a long way, if you ask me) but the real heart of the idea was to avoid transforming an I2S stream to USB and then back again...

Actually one of the mini- or pico-itx boards was top of my list until I saw the beagle board, but all of the above have the problem of import taxes. The avr32 board above looks like a more cost-effective option. Again, if anyone has experience I'd love to hear about it. (A related non-audio question is how do people prefer to set up an interface with the board?)

Cheers

Nigel
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Old 24th June 2010, 02:05 PM   #14
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this board is until 96KHz, not support 192KHz
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Old 27th June 2010, 06:43 PM   #15
gmarsh is offline gmarsh  Canada
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Inside a laptop you'll probably see AC97, not I2S, connecting the audio codec.

With a bit of creativity (using a dsPIC or something) you might be able to grab the AC97 bus, pull out the primary audio signals and convert them to I2S. However, AC'97 runs at a fixed 48KHz sample rate and you're at the mercy of the soundcard driver or southbridge chipset and how well it SRC's its audio to that rate.

I'd go with a USB audio solution. Easier and a whole lot more people have done it that way.
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Old 28th June 2010, 09:13 PM   #16
njepitt is offline njepitt  United Kingdom
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Hi Guys,

Sorry, but it took a while for me to notice this old thread had been revived...

Quote:
Originally Posted by audiodesign View Post
this board is until 96KHz, not support 192KHz
While 192kHz would be nice, I'd still be pretty happy with 96kHz. In any event, do you have another suggestion for 192kHz at a reasonable price? When time and money permit I'd like to go back to these ideas...

Quote:
Originally Posted by gmarsh View Post
Inside a laptop you'll probably see AC97, not I2S, connecting the audio codec.

With a bit of creativity (using a dsPIC or something) you might be able to grab the AC97 bus, pull out the primary audio signals and convert them to I2S. However, AC'97 runs at a fixed 48KHz sample rate and you're at the mercy of the soundcard driver or southbridge chipset and how well it SRC's its audio to that rate.

I'd go with a USB audio solution. Easier and a whole lot more people have done it that way.
As I think I mentioned above somewhere, I've dropped the idea of pulling I2S out of an old laptop as being more trouble than it's worth - in part for reasons similar to those you are giving. When you mention a "USB solution" are you thinking of the TI PCM270* chips? Or something more sophisticated?
I've done a couple of circuits with the PCM2707 (and an Alien DAC with the PCM2702) but the idea of the project was to avoid converting I2S -> USB -> I2S. The board mentioned above should allow an input from the ethernet and a direct output to a I2S DAC such as PCM1793 or PCM1794. without the intermediate USB stage. Or that was the idea, anyway...

For the time being these ideas have taken a back seat to other projects (and in fact work pressure hasn't allowed me to do much diy lately) but I am still giving it some thought, and I'd be interested to read any posts people might have.

Cheers

Nigel
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