Something cool for Raspberry Pi/ODROID: I2S/DSD isolator HAT with native DSD decoder

iancanada

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2009-12-01 1:39 am
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IsolatorPi,something cool for Raspberry Pi/ODROID: I2S/DSD isolator with DoP decoder

I designed a Raspberry Pi I2S adapter a couple of month ago and shared many PCBs for free with this DIY community. http://www.diyaudio.com/forums/digi...mate-weapon-fight-jitter-371.html#post4429205
It was really nice. Community members and I were very happy with it. But I’m still worried about sharing noisy PC ground with audio system.

Another thing is that I'm very interested in playing native DSD music through Raspberry Pi. I’ve heard that the latest version of MPD already has native DSD support. But after downloading the software, I was very disappointed to find that the native DSD is only supported over USB interface. This has also been confirmed by Tim. It means the native DSD feature works only with a USB streamer for now. However that's not the way I use a PRi.

And the third thing is the ODROID. I bought a C1+ because a friend of mine recommended. It has a dedicated I2S port (which is incompatible with PRi). It also runs faster than RPi. I'm quite happy with it. The only issue is that none of the RPi audio gears will work with ODROID because of that I2S port.

So I came up with a new idea: An I2S/DSD isolator HAT with optional native DSD decoder for Raspberry Pi and ODROID.

It will have following functions:

1. To isolate ground and all other signals between RPi/ODROID and audio system.

2. Compatible with both RPi and OROID.

3. Supports native DSD playback by plugging in an optional DSD decoder daughter board. The daughter board will convert DoP stream back into native DSD stream bit-perfect at real-time. In this case, all current SD image such as Volumio, MoodeAudio, RuneAudio, and most others, will have native DSD play-back features.

4. Raspberry Pi DACs and other audio gears will work with ODROID (may need software support for configuration).

5. Has isolated I2C control bus for RPi DACs, as well as optional I2C EEPROM ID bus. It will work very well with all RPi DACs and other audio gears by flowing Raspberry Pi HAT design specification.

Since I'm working on multi-channel I2S/DSD FIFO PCB, hopefully I can place a bulk order.

Here is the block diagram. I will be finishing up this project soon.

Ian

IsolatorPiBlockDiagram
by Ian, on Flickr
 
Last edited:

iancanada

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2009-12-01 1:39 am
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Raspberry Pi/ODROID I2S/DSD isolator HAT PCB layout

Raspberry Pi/ODROID I2S/DSD isolator HAT PCB layout

(J5 is for optional DoP DSD decoder daughter board)
Ian
 

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iancanada

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As you are working on multi-channel Ian - will this just provide a single isolated i2s output from the C2 or multiple? (in my case I'd need three, otherwise I have to go the usb streaming route)

This isolator has ability of another two I2S date signals. But I can not find any software/image for multi-channel application via GPIO. Please let me know if there is any. Thanks.

Regards,
Ian
 

gwing2

Member
2015-03-25 10:18 pm
This isolator has ability of another two I2S date signals. But I can not find any software/image for multi-channel application via GPIO. Please let me know if there is any. Thanks.

Regards,
Ian

I imagine that we would need base audio device drivers for the extra GPIO i2s channels which could then be utilised via alsa and any apps on top of that.

There is some discussion here that they have no real plans to implement multichannel i2s. However the source for their current driver is here [URL="http://https://github.com/hardkernel/linux/commit/ba0b2bf76de2725fcd384f45bf9de7a70c21f8bd" and that does have configuration lines for the number of channels ranging from 1->8 so there is some prep work there.

This unfortunately goes way beyond my level of tinkering - and AFAIK there isn't anything ready built and available.
 
Can other PI HAT DACs be put on top of it??
Or at least would there be a "plug-in" option for a small DAC chip as used by HifiBerry IQaudio asf.

I understand that the main intention behind this project is to provide external I2S DACs
with a quality streaming interface.

However. There is huge number of users out there using and loving HAT DACs because of their simplicity. Usually price/performance ratio is outstanding with these DACs too.
Beside that they are very easy to implement.

I know that your solutions or better, solutions around your high quality gadgets, are usually all but easy to implement. "Easy" in terms of not fiddling around with numerous other boards, regulators, power supplies , cables ...

At least from my perspective it would be nice to have a simple stack and forget "transparency layer" that cleans up the mess between my PI and my HAT DAC.
I do have the feeling though that this project won't supply such a solution.

Perhaps a simple "plug-in" DAC daughter board could be developed.
 

iancanada

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2009-12-01 1:39 am
Toronto
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Can other PI HAT DACs be put on top of it??
Or at least would there be a "plug-in" option for a small DAC chip as used by HifiBerry IQaudio asf.

I understand that the main intention behind this project is to provide external I2S DACs
with a quality streaming interface.

However. There is huge number of users out there using and loving HAT DACs because of their simplicity. Usually price/performance ratio is outstanding with these DACs too.
Beside that they are very easy to implement.

I know that your solutions or better, solutions around your high quality gadgets, are usually all but easy to implement. "Easy" in terms of not fiddling around with numerous other boards, regulators, power supplies , cables ...

At least from my perspective it would be nice to have a simple stack and forget "transparency layer" that cleans up the mess between my PI and my HAT DAC.
I do have the feeling though that this project won't supply such a solution.

Perhaps a simple "plug-in" DAC daughter board could be developed.

Hi soundcheck,

That's a very good point. I have same idea with you.

Yes, this Rpi isolator HAT is originally designed as "transparency layer". That measns all current DAC HAT, such as HifiBerry DAC, DAC+ and DAC Pro, and meany others, will work with this isolator as if there is without this isolator. No any additional overlay or software support will be needed.

By following foundation's HAT specification, all DAC can be stacked on top of my RPi isolator. Because all GPIO connectors and dimensions are as same as a RPi.

So, all RPi DAC users can enjoy this isolator by just simple stacking it over a Raspberry Pi, then their DAC HAT.

It's "easy":). Just hope you are happy with it.

Regards,
Ian
 
Yes, this Rpi isolator HAT is originally designed as "transparency layer". That measns all current DAC HAT, such as HifiBerry DAC, DAC+ and DAC Pro, and meany others, will work with this isolator as if there is without this isolator. No any additional overlay or software support will be needed.


Fantastic Ian! Thanks for sharing this with us. Subscribed!
 
I had the same question in mind.

e.g. My HifiBerry DAC+ Pro uses the poor 3.3V (both pins) from RPI to power VDD and the clocks. And that's hardwired.

As far as I understood Ians blockdiagramm there'll be a clean 5V and 3.3V made available.
That seems to cover my situation.

But then I'm asking myself what supply voltage would be required for the board on the
clean side. Obviously something >5V e.g. 7V minimum DC would be needed.