I2S has me confused - diyAudio
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Old 8th May 2008, 02:37 AM   #1
jkeny is offline jkeny  Ireland
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Default I2S has me confused

Is I2S simply a method for signal delivery keeping the clock signals seperate from the data signals by using 4 seperate wires?

It specifies nothing about the data format?

Can somebody help me then with trying to take the I2S output from a PCM2706 DAC to a SAXR57 Digital amp?

The relevant page from the PCM2706 datasheet is attached
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File Type: pdf pcm2706 i2s output.pdf (20.2 KB, 79 views)
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Old 8th May 2008, 02:48 AM   #2
jkeny is offline jkeny  Ireland
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The relevant page from the AK4114 IC datasheet attached. This is the first place I think I can splice the I2S signal into but the chip is hardwired to mode 0. Am I right in thinking that mode 7 is the only one that would work for what I want?
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File Type: pdf ak4114 input data modes.pdf (19.2 KB, 42 views)
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Old 9th May 2008, 01:20 AM   #3
jkeny is offline jkeny  Ireland
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I know this is a very specific question so let me broaden it !

What is I2S ? To what extent does it define the format of the data?
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Old 9th May 2008, 09:21 AM   #4
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http://www.nxp.com/acrobat_download/various/I2SBUS.pdf
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Old 14th May 2008, 01:15 PM   #5
jkeny is offline jkeny  Ireland
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Thanks rfbrw,

I have further issues - I've connected a PCM2706 I2S output into a Panasonic digital amp SAXR57 where the A/D converter (PCM1804) would normally output I2S - all I get is loud white noise!

I've lifted the 4 I2S output pins of the PCM1804 chip & connected my I2S signal to the lines MCLK, LRCK,BCLK, DATA.

I measured DC on the I2S pins coming from the PCM2706, as follows:
Dout (data) about 20mV
BCK 1.5V DC
LRCK 1.5V DC
SCK 1.5V DC

Is this correct? Any suggestions?
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Old 14th May 2008, 01:57 PM   #6
jkeny is offline jkeny  Ireland
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Is my problem that I have SCK connected?
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Old 14th May 2008, 06:25 PM   #7
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You really need a 'scope to look at the signals but assuming they are present you need SYSCK from the PCM2706 not to be in contention with any clock signal sent to the PCM1804. Looking at datasheets, for the PCM1804 SCKI is an input whereas SYSCK is an output on the PCM2706.
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Old 14th May 2008, 07:17 PM   #8
jkeny is offline jkeny  Ireland
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Thanks again, Rfbrw,

I will disconnect SCK tonight & give it a try!
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Old 14th May 2008, 09:34 PM   #9
jkeny is offline jkeny  Ireland
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Tried with SCK disconnected - different quality of white noise but no music! I'm stumped!
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Old 14th May 2008, 09:49 PM   #10
jkeny is offline jkeny  Ireland
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Ah, could it be that PCM1804 output 24bit I2S & PCM2706 ouputs 16bit I2S. So the DIR (AK4114) that's receiving the I2S signals is set to expect 24bit & I have no way of changing this.

Is there anything I can do?
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