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#248552 - 05/02/2005 22:28 need software help with digital aux-in
jv8
new poster

Registered: 01/12/2003
Posts: 11
I'm working on a digital aux-in project. I've been using the Eutronix digital out board for a while now and wanted to add digital in from my XM unit.

I lifted the CD2 input pins of the 7705 DSP and routed an I2S signal in from the XM unit. I then modified the hijack kernel DSP programming in empeg_mixer.c to select CD2 when aux-in is selected.

However, there seems to be some sort of issue with a mute function. When I turn on the XM unit I get an audio click and then silence. The display will increment "XM 1", "XM 2", etc... so I know it's seeing something.

I know the CS4231A can be programmed to sample the analog aux in and display bar graphs, etc. If no analog signal is seen, will it automatically mute? If so, where is this code?

Thanks for the help...
-Jon

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#248553 - 06/02/2005 12:55 Re: need software help with digital aux-in [Re: jv8]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 14472
Loc: Canada
You can see what the player s/w is doing much of the time by running it under "strace" (need to compile it and upload to the player).

This works best on an upgraded-memory unit, but may still do the job on a 16MB player if ReserveCache=96 is used. Oh, a copy of the strace.binary for the Empeg is here.

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#248554 - 06/02/2005 19:01 Re: need software help with digital aux-in [Re: jv8]
jv8
new poster

Registered: 01/12/2003
Posts: 11
Well, after further investigation I believe the software hack is fine but I have signal integrity issues. I was able to get the digital aux to work for brief moments on the bench. By "work" I mean the empeg bar graph lit up and I witnessed bits going from the DSP to my digital out board. In the car it was hopeless.

To be fair, my method of communication is a hack. The real solution would be an SPDIF board in the XM unit, and a corresponding SPDIF receiver (reverse of the Eutronix board) in the empeg. Right now I'm running a simple single ended driver/receiver pair for the I2S signals (WS,CLK,DATA).

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#248555 - 06/02/2005 21:02 Re: need software help with digital aux-in [Re: jv8]
jv8
new poster

Registered: 01/12/2003
Posts: 11
I can now confirm the software hack works great! I've been listening to digital aux-in reliably on the bench now for a while. The level bar graphs even work well.

Good time to take a break and watch the super bowl. Hopefully this week I can clean up the in-car signal quality and install this permanently.

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#248556 - 06/02/2005 21:45 Re: need software help with digital aux-in [Re: jv8]
Mach
old hand

Registered: 15/07/2002
Posts: 828
Loc: Texas, USA
Very cool! Please keep us updated. I just got my tuner module and assorted cables for the testing on my desktop. Let me know if I can help.

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#248557 - 23/02/2005 19:54 Re: need software help with digital aux-in [Re: jv8]
altman
carpal tunnel

Registered: 19/05/1999
Posts: 3457
Loc: Palo Alto, CA
ISTR the digital in pins are on the docking connector (well, CLK, DATA & WS), two of them multiplexed onto the analogue signal/signal strength pins and one separately.

This might be a bit easier than lifting pins? ISTR that they might be inverted though (input buffers).

Hugo

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