exaU2I - Multi-Channel Asynchronous USB to I2S Interface
 

Hi Everyone,

I’ve been working on a new design for 8-channel Asynchronous USB to I2S interface. It started as a fun project and eventually became more involving than just a hobby. A couple of friends joined in and helped with the development of bit-perfect ASIO driver covering all sampling rates up to 352.8 kHz. At the present time I am testing it with a ES9018 DAC.

Here are the details:
• Sampling frequencies (kHz): 44.1, 48, 88.2, 96, 176.4, 192, 352.8
• Resolution (bits): 16, 24, 32
• 8, 4 or 2 channels for sampling rates up to 192 kHz
• 4 or 2 channels for 352.8 kHz
• Galvanic isolation between the USB ground and the I2S outputs.
• Two quartz oscillators for the 44.1 kHz and 48 kHz sampling rate groups
• FPGA implementation
• 256 kB FIFO buffer to support asynchronous operation
• Two analogue voltage regulators with filters
• Sample rate LED indicators
• USB power LED indicator
• Buffer level LED indicator
• Four I2S data outputs (8 channels) powered by the DAC power supply (3.3V or 5V)
• USB 2.0 interface, Mini USB connector
• Proprietary bit-perfect ASIO driver completely independent from the Windows sound system; No software volume control or mixing.
• ASIO driver implements automatic sampling rate switching; no re-sampling
• Works on Windows XP, Windows Vista and Windows 7.
• Tested with Foobar and J.River Media Center
• Project homepage – http://www.exaDevices.com

I am about to make the USB to I2S interface commercially available as a kit.

Any feedback is highly appreciated.

OS X version?

Why not firewire?

dave

Are you using Vbus to power any on-board devices?
FPGA used?
Price & Kit contents i.e fully built or part-built or board + parts?

Hi Dave,
OS X drivers are on the to-do list.

FireWire in my opinion is a matter of convenience. It will make the device more expensive. Asynchronous mode of operation will work equally well with FireWire, USB or Ethernet. I’d like to hear more about the need for FireWire.

exa

jkeny,
We are not using vBus. The kit will be fully built. Sorry, features and pricing are not finalized yet.

1/ seems that a bus designed for media makes more sense than one where media is an afterthot.
2/ in my experience it works better

It trades some hardware development (firewire) for software development (USB).

dave

What you have listed in the first post is great Exa. Let us know pricing and availability.

Great project! hope price comes out good to ;)

Thank you, Dave. There is more than one way to do it right.
It was a design decision not to use a media interface. Making a proprietary solution gave us a complete control. We can go as high as 352.8 kHz sampling rate and we can verify bit-perfect operation in the driver and in the hardware. Ultimately what really matters for sound quality is the true asynchronous operation.

exa

How many channels can it support?

dave