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Moonshadow XMOS DAC - No I2S Output
Moonshadow XMOS DAC - No I2S Output
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Old 28th July 2018, 08:53 PM   #1
snoopy33 is offline snoopy33  Ajman
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Default Moonshadow XMOS DAC - No I2S Output

Hi,

Does anyone have one of these boards working?

XMOS数字界面板,CPLD波形重整技术-月影科技

They are popular on aliexpress.

I'm using Linux, so no drivers required, and I'm feeding the I2S lines into a ES9028Q2M board which I've verified is working correctly.

And... no output.

Did a quick test of the output pins and have:

Data 3.28v
BCK 1.64v
LRCK 1.64v
MCK 1.64v

Which appears to be correct. A bit stumped.

Aliexpress seller was helpful until the protection ran out, which I didn't catch, then unsurprisingly silent.

Regards,

Andrew
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Old 29th July 2018, 11:28 AM   #2
percival007 is offline percival007  England
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Not familiar with Linux, so first things first, are you sure your USB (?) source is 'talking' to the PCB?

Are they talking the same Language? i2S can have a few 'dialects' ! Left Justified etc etc.

Have you a 'scope? Can you actually see some Data and Clocks on the i2S Lines? Those are just DC Voltages you quote which could be there when powered even with no Signal.

Cheers,

P.
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Old 29th July 2018, 11:36 AM   #3
abraxalito is online now abraxalito  United Kingdom
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If those voltages are what you got from a DVM then the 'Data' voltage looks suspicious (too high), the others are fine (as they're clocks at 50% duty cycle).
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Old 29th July 2018, 11:39 AM   #4
snoopy33 is offline snoopy33  Ajman
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Hi, I used a PCM2704 based converter to ensure the DAC (a ES9028Q2M) is working, so the issue is with the XMOS USB-I2S.

For the XMOS, it's recognised fine. I've tested on Linux and Windows with same result so don't think it's a driver issue.

I note the 1.64V lines are the same as the output of the PCM2704 (1.64V is probably the digital on/off averaged by the multimeter). Whether they're talking the same I2S "variant" I'm unsure, but I'd like to hope so.

I don't have a scope but I do have a data recorder good for 20MHz. If I2S lines are less than this I can try capturing. Worth a shot!
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Old 29th July 2018, 11:41 AM   #5
snoopy33 is offline snoopy33  Ajman
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Quote:
Originally Posted by abraxalito View Post
If those voltages are what you got from a DVM then the 'Data' voltage looks suspicious (too high), the others are fine (as they're clocks at 50% duty cycle).
Thanks Abraxalito, I agree it initially raised an eye-brow. I've checked and it's not shorted with the 3.3V line. I'll get the data recorder onto it first.
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Old 29th July 2018, 11:53 AM   #6
snoopy33 is offline snoopy33  Ajman
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Results:

Data is 0V when not playing (my error earlier). Once playing I can see signal. Looks clean
BCK is a square wave signal with some roll on/off. Not the cleanest.
LRCK is a similar square wave but much cleaner than BCK.

So indeed looks like a compatibility issue.
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Old 29th July 2018, 12:04 PM   #7
snoopy33 is offline snoopy33  Ajman
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Default Pictures

Pictures attached
Attached Images
File Type: png lrck.png (18.0 KB, 132 views)
File Type: png data.png (23.1 KB, 131 views)
File Type: png bck.png (17.8 KB, 132 views)
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Old 29th July 2018, 12:09 PM   #8
abraxalito is online now abraxalito  United Kingdom
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Those three signal plots look reasonable for I2S running at 2.8MHz BCK (so 32 bits per channel).
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Old 29th July 2018, 01:50 PM   #9
snoopy33 is offline snoopy33  Ajman
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Thanks.

I've tried WIndows 7, 10 and Linux now, same on all.

It looks to me the I2S signal is malformed in some way.
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Old 29th July 2018, 03:17 PM   #10
canvas is offline canvas  Taiwan
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It should work unless DOA. I've seen people using this USB bridge and claimed having better performance than regular XMOS.
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