Hi everybody,
I am planning to build a HD audio player (with digital output only) using single board computer (such as RPi). Provided I need a SATA connector on-board I decided to use Cubietruck as it exposes A20's I2S pins and allows to connect a SATA device.
I did some research and now I am pretty sure that connecting an I2S device to Cubietruck should not be a problem -> http://hifiduino.wordpress.com/2014/03/07/cubieboard-for-audio/
The question is what other pins/interfaces Digi is using (I'm trying to find any specs)? Is it also utilizing I2C bus? Will I be able to use it with Cubietruck when I connect proper pins?
What possible difficulties can I meet? I won't be using raspbian os but lubuntu probably, are there kernel modules that I can compile with? What I found it is supported starting from kernel version 3.10.23 (source: http://www.hifiberry.com/products/digi-connect-your-external-dac/hifiberry-digi-software-installation/ ).
Thanks!
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10 comments
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hifi I believe Cubietruck has SPDIF output. I'm not sure about all models though.
Why do you need Digi in this case? -
HiFiBerry team Dear Pawel,
even if the board has an I2S interface that does not mean you can just connect an I2S chip. Everything needs to be configured correctly. Therefore it needs a device driver for this. The I2S subsystem from the Raspberry Pi won't work on other CPUs. It is not an easy task to do this. The whole hardware driver has to be developed for the Cubieboard.
The easiest solution will be a Raspberry and a USB->SATA bride (like it is included in every external harddisk).
Best regards
Daniel -
Paweł Gabryelewicz Yes, it has an optical SPDIF output but due to chipset hardware limitations we can play 16-bit audio only. As I wrote before I am interested in HD audio player (with 24-bit/192 kHz output) which is only possible with I2S-based interface. -
hifi Got it. Hopefully those hardware limitations happen after I2S
not before :) -
Paweł Gabryelewicz Hi Daniel,
Thank you for your answer. I was considering such solution. Cubieboard also has some nice features (like gigabit LAN on-board, bluetooth, wifi etc) - that's why I was interested in building such device not based on RPi. I basically understand how I2S works (I am a software developer and linux administrator) so I know it may take some time and effort to work.
Back to my question - what pins from P1 Digi's using?
Regards,
Pawel -
HiFiBerry team It uses the I2C pins (3 and 5).
Best regards
Daniel -
hifi Probably this info will be interesting for you:
http://volumio.org/volumio-audiophile-music-player-for-cubietruck-is-out/ -
HiFiBerry team The problem is still that the I2S interface and the sound chip have to be configured correctly. I2S is not a simple plug-and-play interface, but an interface where both endpoints must have exactly the same understanding about the signals (what frame rate, how many bits per frame, who is master for which signal). Thinking about I2S as a standardized interface is unfortunately a bit misleading.
Best regards
Daniel -
Paweł Gabryelewicz Hello again,
If I undestand correctly, we have to setup and control the WM8804 chip via I2C.
So if we manage to compile similar kernel-mode audio driver on Lubuntu for Cubietruck, we should be able to handle Digi properly. What I have found, most of the things rely on this:
https://github.com/raspberrypi/linux/blob/15d7e6373f54b99fce2ba5375b75cc11549af751/sound/soc/bcm/hifiberry_digi.c
It's rather not sophisticated, just some basic data are being sent to the chip.
As far as I know, the I2S driver already compiles on Cubietruck so there are only few things to port to a different CPU (instead of BCM2708).
Correct me if I am wrong.
Regards,
Pawel -
HiFiBerry team Hi Pawel,
these few things can be quite difficult. There is lot of talking about "I2S drivers". Not sure, if all these drivers really implement the full configuration options for I2S (clocks, framerates, master/slave configurations). As I don't know the state of the I2S subsystem for the Cubietruck, I can't say how hard this will be. If you get it running, we are very interested to learn what you did.
Best regards
Daniel
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