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XMOS-based Asynchronous USB to I2S interface
XMOS-based Asynchronous USB to I2S interface
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Old 1st December 2018, 06:27 PM   #3191
Ryelands is offline Ryelands  United Kingdom
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Quote:
Originally Posted by Rax View Post
I assume the 16 bits limitation of the chip stays in place and will apply to any incoming signal.
Better for Lorien or others who use variable data rates (I don't) to answer your query on the WaveIO but, yes, the TDA1543 is 16-bit maximum.

D
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Old 8th January 2019, 07:49 AM   #3192
deduikertjes is offline deduikertjes  Netherlands
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Default non isolated i2s and J1 questions

I'd like to try the non-isolated I2S lines. I couldn't find any info on the connection of the earth on the dac side. Do the earth lines need to be connected to the DAC chip (a TDA1543 in my case), or can I leave them unconnected?

J1 chooses between internal and external USB input. Can I put a few wires and a switch on it to bring it to the front panel, or does this degrade sound quality? As an alternative I can use a small relay of course but I rather avoid that hassle.

Thank you, MArco
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Old 9th January 2019, 11:06 AM   #3193
Lorien is offline Lorien
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Hello Marco,
'earthing' your DAC is a long story. I would start by omitting it. That doesn't mean that it should be ignored but in my head fewer connections means higher chances to debug the issue when something is not working properly - programmer thinking.
J1 does NOT switch between external or on-board USB. it's only a physical header allowing you to connect your USB extension cable to your WaveIO.

J8 is the one you are looking for! Placing J8 on "EXT" position, your WaveIO will communicate with host through J1 pin header. Keeping J8 jumper on "BRD" position will make WaveIO using the on-board USB connector. This is the default option for your board. Please note that wiring an external USB cable to J1 without moving J8 to "EXT"ernal position will not to too much for you!


Soldering some wires to J1 is the best option since contacts can oxidize over time thus creating USB data transfer troubles.
STILL, please use an ESD protected soldering iron otherwise you could risk damaging the USB data multiplexer chip.
No relays on USB cables please! Do not put relays on USB data lines as you will definitely degrade the signal's integrity (relays, wires and related parasitic caps will not help you)! Moreover, WaveIO does need +5V form the USB cable to correctly pass through enumeration process so it would be better to leave that alone too

Kind regards,
L


EDIT: J8 and J12 are two different jumpers addressing two different things: J8 is for choosing USB connection path while J12 is for power options: 5V from external PSU or USB bus. Please address them separately!
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Last edited by Lorien; 9th January 2019 at 11:09 AM.
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Old 9th January 2019, 11:12 AM   #3194
deduikertjes is offline deduikertjes  Netherlands
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Quote:
Originally Posted by Lorien View Post
Hello Marco,

Hello Marco,
'earthing' your DAC is a long story. I would start by omitting it. That doesn't mean that it should be ignored but in my head fewer connections means higher chances to debug the issue when something is not working properly - programmer thinking.

J8 is the one you are looking for! Placing J8 on "EXT" position, your WaveIO will communicate with host through J1 pin header. Keeping J8 jumper on "BRD" position will make WaveIO using the on-board USB connector. This is the default option for your board. Please note that wiring an external USB cable to J1 without moving J8 to "EXT"ernal position will not to too much for you!
Thank you. I'll start with those earth lines not connected.
By the way, does this non-isolated i2s do 3.3V or 5V?

Sorry for the confusion. Yes, I meant j8. Can I add a switch to there and bring that with wires to the front panel, or should I minimize wiring there by utilizing a relay?
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Old 9th January 2019, 03:27 PM   #3195
Lorien is offline Lorien
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Non-isolated I2S lines are drive directly by the XMOS processor and cannot go higher than 3.3V under normal operations since XMOS I/O lines are powered form a 3.3V Vreg.
Switch: yes, you can safely add a switch on that J8 pin header since it's a simple selection signal. As long as it's not dangerously close to a heavy current wire (like those coming from a secondary of your DAC's trafo) it should be fine. The pull up on that line is 10K which is reasonable.
For safety reasons I recommend you to use the GND as the same one used by your WaveIO (found on mounting hole H4 or J13 gray power connector).


I hope it helps,
L
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Old 13th January 2019, 11:56 AM   #3196
deduikertjes is offline deduikertjes  Netherlands
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Default non-isolated I2S

I am happy to inform you that connecting the non-isolated i2s lines directly to my TDA1543 DAC WITHOUT connecting the earth lines worked right away.

With the same DAC chip in only a slightly different arrangement than using the isolated i2s I hear more refinement and detail.

In this case it might be interesting to know that I feed my waveio from a wandboard mini computer with only the USB data lines connected. Wandboard, waveio and dac earth are all on a star like arrangement in the power supply.
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Old 13th January 2019, 03:10 PM   #3197
phi112358 is offline phi112358
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I have a question about the asynchronous USB to i2s converters. Is it better to use a separate PSU if the DAC already has its own dedicated PSU?
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Old 14th January 2019, 10:40 AM   #3198
Lorien is offline Lorien
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@ deduikertjes: Happy to know that! Looking forward for your results related to earthing your DAC.

@ phi112358: Yes! definitely! in fact it is better to have a PSU for each power rail! Maybe some does consider this redundant (including me, sometimes) but this way the influences between stages (USB board and DAC) are kept to minimal. Moreover, is better to have two PSUs that are working "relaxed", one for USB and the other for your DAC than having only one who, perhaps, are working stressed (sourcing bigger current). This way the power dissipation is distributed, maybe temps are not so high, involved parts will have a prolonged life and list can go on...
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Old 14th January 2019, 10:50 AM   #3199
Extreme_Boky is offline Extreme_Boky
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Quote:
Originally Posted by deduikertjes View Post
I am happy to inform you that connecting the non-isolated i2s lines directly to my TDA1543 DAC WITHOUT connecting the earth lines worked right away.
That ain't possible.... unless

Quote:
Wandboard, waveio and dac earth are all on a star like arrangement in the power supply.
....which is a loooong ( mostly dirt and gravel) way for the I2S signal returns to find their way back to XMOS chip....
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Old 14th January 2019, 11:05 AM   #3200
deduikertjes is offline deduikertjes  Netherlands
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Quote:
Originally Posted by Extreme_Boky View Post
That ain't possible.... unless



....which is a loooong ( mostly dirt and gravel) way for the I2S signal returns to find their way back to XMOS chip....
You have a better suggestion?
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