[sdiy] $53 Intel Edison dual 500MHz Atom 1GB RAM SOC board has I2S + Intel Xeon Phi 72 core . . .

[Robin Whittle]

Summary:

  1 - The I2S interface is not documented, in part at least due to
      Intel not yet having verified that it works according to its
      design.  (I guess they cut and pasted some VHDL into the
      design and will get around to testing it any month now.)

  2 - There's no ALSA code to support the I2S interface - nor do there
      seem to be concrete plans to create this.

2 is not surprising considering 1!


I think this thread:

 (1)  https://communities.intel.com/thread/56958

probably sums up the current state of I2S drivers for the Intel Edison.

AlexT of Intel apparently has ALSA installed in the kernel, and
apparently instructs on how to do this at:

 (2)
http://alextgalileo.altervista.org/blog/install-kernel-from-repo-onto-edison-official-image/
 (3)
http://alextgalileo.altervista.org/edison-package-repo-configuration-instructions.html
 (4)  https://communities.intel.com/message/261851#261851

however, at the end of (2), in a message of 2014-11-21, he writes that
it would be best to use a USB sound card (not the I2S interface).

In (1) he wrote (2014-11-17):

    You need to use the USB sound card or equivalent device (I
    used a USB headset, for example, it can be e.g. an external
    DAC) - that is the approach I had in mind, it's probably
    the cheapest and most straightforward one.

    You probably can buy or create a sound card using i2c or SPI
    buses too, but that would be noticeably more advanced stuff.

I think the natural place to find kernel drivers for the Intel Edison
I2S interface is the ALSA SoC Layer:

  http://www.alsa-project.org/main/index.php/ASoC

However, at present there's no mention of the Edison.

I haven't seen any low-level hardware doco for the Edison, such as I/O
register locations - which would include details of how to drive the I2S
interface.  Maybe that information has not been released yet.

The silicon is certainly ahead of the software - for instance the Quark
Pentium-like microcontroller is there, but it will be some time in 2015
before Intel releases details or software which enable it to be used.

So I guess the silicon is ahead of the documentation and the IS2 work
required for ALSA to support it.


There's a thread

  https://communities.intel.com/thread/57474

with recent comments from an Intel person (2014-11-27):

   I’d suggest you try to configure I2S on Linux side, but
   unfortunately for the moment there is no documentation
   on it nor has been validated.

So in the rush to get this product out, maybe they have not yet got
around to testing the I2S interface.


Here is the most detailed information I have found about the 12S
interface, on page 16 of the September 2014 "Intel Edison Module
Hardware Guide":


https://communities.intel.com/servlet/JiveServlet/previewBody/23158-102-3-27299/edison-module_HG_331189-001.pdf


The table lists the modes, frame rates, sample bits, number of samples
etc. with the note:

   An I2S interface is available on pins 50, 52, 54, and 56.
   All of the I2S modes below have not been verified and are
   subject to change.


So it is early days yet, with direct Audio connections to a CODEC
obviously not near the top of Intel's priorities.

  - Robin