Interfacing I2S/SPI to USB

fatspan · 3rd December 2009, 02:32 AM

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 · 3rd December 2009, 03:21 AM

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 · 3rd December 2009, 06:24 PM

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 · 4th December 2009, 12:07 AM

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

gooki · 4th December 2009, 07:30 AM

Quote:

Originally Posted by fatspan

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 · 8th December 2009, 11:22 PM

Search TI's site for USB Streaming Controllers.

fatspan · 9th December 2009, 01:37 AM

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

3rd December 2009, 02:32 AM	#1
fatspan diyAudio Member Join Date: Dec 2009	Interfacing I2S/SPI to USB 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

4th December 2009, 12:07 AM	#4
star882 diyAudio Member Join Date: Mar 2007	Use a small CPLD or FPGA to convert SPI to I2S. __________________ "Fully on MOSFET = closed switch, Fully off MOSFET = open switch, Half on MOSFET = poor imitation of Tiffany Yep." - also applies to IGBTs!

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3rd December 2009, 03:21 AM	#2
Iain McNeill diyAudio Moderator Join Date: Oct 2007 Location: Santa Cruz, California	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?

3rd December 2009, 06:24 PM	#3
fatspan diyAudio Member Join Date: Dec 2009	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

8th December 2009, 11:22 PM	#6
TheSeekerr diyAudio Member Join Date: Jan 2008	Search TI's site for USB Streaming Controllers.

9th December 2009, 01:37 AM	#7
fatspan diyAudio Member Join Date: Dec 2009	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

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