I2S has me confused

jkeny · 8th May 2008, 01:37 AM

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

jkeny · 8th May 2008, 01:48 AM

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?

jkeny · 9th May 2008, 12:20 AM

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?

rfbrw · 9th May 2008, 08:21 AM

http://www.nxp.com/acrobat_download/various/I2SBUS.pdf

jkeny · 14th May 2008, 12:15 PM

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?

jkeny · 14th May 2008, 12:57 PM

Is my problem that I have SCK connected?

rfbrw · 14th May 2008, 05:25 PM

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.

jkeny · 14th May 2008, 06:17 PM

Thanks again, Rfbrw,

I will disconnect SCK tonight & give it a try!

jkeny · 14th May 2008, 08:34 PM

Tried with SCK disconnected - different quality of white noise but no music! I'm stumped!

jkeny · 14th May 2008, 08:49 PM

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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9th May 2008, 12:20 AM	#3
jkeny Banned Join Date: Feb 2007 Location: Dublin	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?

9th May 2008, 08:21 AM	#4
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	http://www.nxp.com/acrobat_download/various/I2SBUS.pdf

14th May 2008, 12:15 PM	#5
jkeny Banned Join Date: Feb 2007 Location: Dublin	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?

14th May 2008, 12:57 PM	#6
jkeny Banned Join Date: Feb 2007 Location: Dublin	Is my problem that I have SCK connected?

14th May 2008, 05:25 PM	#7
rfbrw diyAudio Member Join Date: Oct 2001 Location: .	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.

14th May 2008, 06:17 PM	#8
jkeny Banned Join Date: Feb 2007 Location: Dublin	Thanks again, Rfbrw, I will disconnect SCK tonight & give it a try!

14th May 2008, 08:34 PM	#9
jkeny Banned Join Date: Feb 2007 Location: Dublin	Tried with SCK disconnected - different quality of white noise but no music! I'm stumped!

14th May 2008, 08:49 PM	#10
jkeny Banned Join Date: Feb 2007 Location: Dublin	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?