Interfacing I2S/SPI to USB

[fatspan]

Hi

I am currently working on a USB signal acquisition module which has to be able to have at least two input and two output channels. I am working under the assumption that I will need ADC's, DAC's and a USB interfacing chip. So far I have found that the majority of data converters in the high quality 24 bit sampling region use I2S bus. I was wandering if anyone knew how these data converters normally communicate with PC's. I currently have access to a USB interface with SPI and UART ports, although I am finding it hard to find a DAC with an SPI data port.

Just wandering if anyone knows the norm for this kind of system?

Any help greatly appreciated

Dan

 

[Iain McNeill]

Micronas has a wide range of USB ADC/DAC's I would guess TI and AD do also.

Failing that, you need to set up a buffer and then serial stream the data out onto I2S. Buffer management is the problem with USB. Are you using isochronous USB or bulk?

 

[fatspan]

Hey
Thanks for the swift reply, I'm having trouble locating any kind of product list from Micronas, would it be possible to post a link maybe, I only came across their MAP-M device which does have many nice features but no USB connectivity.

As for streaming the data onto I2S I'm not sure I quite understand your point. The USB interface that I have can communicate only via SPI or UART (or I2C but I understand that this is even more useless for this application) I think this is synchronous communication but I could be wrong....

Analog and TI certainly have a wide range of A/D's but anything near audio quality seems to use this I2S format which I can't find out how to interface with USB.
I did find a suitable A/D from Analog which uses SPI (AD7764) but there is no equivalent quality D/A.

Thanks again for the help

Dan

 

[star882]

Use a small CPLD or FPGA to convert SPI to I2S.

 

[gooki]

Analog and TI certainly have a wide range of A/D's but anything near audio quality seems to use this I2S format which I can't find out how to interface with USB.

CMedia has sound chips that will interface between USB and I2S in/out.

 

[TheSeekerr]

Search TI's site for USB Streaming Controllers.

 

[fatspan]

Thank you everyone for your suggestions. I have researched into the FPGA, CPLD approach although I'm thinking it might be a little out of my skill rang, I know a little VHDL but I don't know how far this will get me and I also noticed Altera have posted a solution with their Max II CPLDs. As for Cmedia, that was a very helpful find, although I'm thinking the sound quality of the devices may be a little low for my needs.
Can anyone suggest a suitable CPLD/FPGA that would be able to be programmed to give me multiple channels to convert I2S to SPI, so basically for example 4 I2S bus in and 4 SPI out, all independent?
Thanks again evryone
Dan