continuous-play DAC

Apr 02, 2012 8 Replies

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John Larkin 14 years ago

Hi,

We have a customer who has a mess of digitized data from some sort of aircraft system, and wants to play it back into some box for testing. It will be 2 channels of 16-bit data originally sampled at about 500 KHz, several hours worth. They want us to design a VME module with dacs and a huge amount of DRAM to store the data. We don't really want to do it - they only need a couple of boards - but we don't like to say no to these guys either.

So, couldn't he just use a small-box PC and a sound card? How fast can a high-end sound card output points? The CD standard was 44KHz, but I think there are 4x versions at least. Depending on his analog bandwidth requirements, 196K might work.

Can a fast sound card accept data at the 4x (or whatever) rate, or does it always accept 44K data and interpolate?

Who makes good high-end sound cards?

Thanks

John

John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation

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Tim Wescott 14 years ago

If you want to do this with the least muss and fuss, your best off-the- shelf solution is probably something from National Instruments or DAQ.

I'm just guessing -- but I'd look there first.

Tim Wescott Control system and signal processing consulting www.wescottdesign.com

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Nico Coesel 14 years ago

500kHz, 16 bits and 2 channels adds up to 4MB/s. I'd go for an SD card and an NXP ARM controller. Use an SPI DAC and use the SPI timing to get the sample rate right. Piece of cake :-)

Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------

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Martin Riddle 14 years ago

Direct Stream digital recording is interesting....

pretty cheap recorder...

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Uwe Hercksen 14 years ago

John Larkin schrieb:

Hello,

5 hours with 500 kHz sampling rate, 2 channels with 2 bytes each will need about 36 GB of RAM. So look for a small-box PC with 40 GB of RAM and 64 bit adressing. Or a disk with more than 2 MB per second data rate, sustained for hours.

Bye

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langwadt 14 years ago

you don't need all that ram, most PCs will play HD video just fine so bandwidth from disk shouldn't be an issue

I wonder if you could graft an SD card onto one of your arbitrary waveform generators it is basically spi so it not that many pins and if the data on it is just a big flat file it shouldn't be that hard to read from an FPGA

or maybe something like this:

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-Lasse

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bitrex 14 years ago

24 bit 192kHz sample rate soundcards are commodity hardware these days:

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among many others.

They can playback 192kHz sample rate files, no interpolation needed.

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Ralph Barone 14 years ago

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I wouldn't bet much on the analog output of this being flat up to 90-odd kHz.

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josephkk 14 years ago

AodPC6x0g

And that ain't half the incoming sample rate. 500 ksps. Playing with a small disk and an arb sounds like the way to go.

?-)

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