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How to make an HDA Dongle for Front Audio Support

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October 18, 2006 2:42:37 PM

All,
I've got an issue that both the case maker and motherboard maker have punted on.

I've got a Foxconn nForce 590 SLI that only has an HDA connector for the front audio ports.

I've got an Antec p180 that has AC97 dongle coming out of the front audio ports.

I've connected the wires so that sound comes out, but its missing all of the HDA features like turning off the speakers when the headphone jack is detected which is a real pain. Antec says "too bad" we don't offer an HDA connector. Anyone have any insights into how to build my own?

Thanks.
October 18, 2006 2:59:40 PM

Looking into it, it seems that there is special hardware required.

Pinouts;

http://www.intel.com/support/motherboards/desktop/sb/cs...

Pin Signal Name Description
1 PORT 1L Analog Port 1 - left channel (Microphone)
2 GND Ground
3 PORT 1R Analog Port 1 - right channel (Microphone)
4 PRESENCE# Active low signal that signals BIOS that an Intel® HD Audio dongle is connected to the analog header. PRESENCE# = 0 when an Intel® HD Audio dongle is connected
5 PORT 2R Analog Port 2 - right channel (Headphone)
6 SENSE1_RETURN Jack detection return for front panel (JACK1)
7 SENSE_SEND Jack detection sense line from the Intel® HD Audio CODEC jack detection resistor network
8 KEY Connector key
9 PORT 2L Analog Port 2 - left channel (Headphone)
10 SENSE2_RETURN Jack detection return for front panel (JACK2)


For AC-97 Front Panel Audio
Pin Signal Name Description
1 MIC Front panel microphone input signal (biased when supporting stereo microphone)
2 AUD_GND Ground used by analog
3 MIC_BIAS Microphone power / additional MIC input for stereo microphone support
4 AUD_GND Ground used by analog audio circuits
5 FP_OUT_R Right channel audio signal to front panel (headphone drive capable)
6 FP_RETURN_R Right channel audio signal return from front panel (when headphones unplugged)
7 AUD_5V Filtered +5 V used by analog audio circuits
8 KEY No pin
9 FP_OUT_L Left channel audio signal to front panel (headphone drive capable)
10 FP_RETURN_L Left channel audio signal return from front panel (when headphones unplugged)

I think you're out of luck :( 
October 18, 2006 3:20:14 PM

Thanks, Mkaibear. Yeah, I checked out all the pins on the Intel site and it turns out that AC97 is "compatible" with HDA but not full-featured.

If someone sold a front audio port by itself, I'd be glad to break out the soldering iron and make an HDA dongle. I just can't find any electronics site that sells stand-alone front audio jack (and Antec has been less than helpful).

Thanks again.
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January 16, 2009 3:40:38 AM

I've come across this issue a number of times in searching for an proper HD solution.

Disabling front panel detection works for some folks with driver support, but I understand that some functionality is lost; specifically the speaker out isn't cutoff when the headphones are connected. I'd really like to build a solution for an existing case. The problem is in the document found at http://www.formfactors.org/developer/specs/A2928604-005.... The connectors for the front panel audio have changed internally.

In an AC97 panel shown on page 20 the connectors at Tip and Ring inside (the 1/8" TRS/stereo connector) are NC/Normally Closed and when a plug is inserted the circuit is interrupted. This disconnects/reroutes the audio to/from the device plugged in. With HD Audio there is a NO/Normally Open design; so when a plug is inserted the ring connector is pushed out and it closes another circuit so the signal at pin seven is connected to the sense1_return (pin 6) or sense2_return (pin 10) shown on page 25.

Wouldn't it be nice if we could mod our cases if we had the right 1/8" connectors and the inclination to mod the dongle board they are attached to? Wouldn't that be the right way? If only I could find the right connectors. That seems to be the hard part.

Just a thought. If anyone has had any luck with this I'd love to hear from you. Post to this thread and I'll be notified.

Thanks,
David
January 17, 2009 4:14:59 AM

David, virago81, the magic thing you are looking for is not that hard to find. Just go to http://www.cui.com/ and search for Connectors > 3.5 mm Audio Jacks. SJ-356X series is what you need. For example this one: http://www.cui.com/pdffiles/SJ-3566AN.pdf

Right now I am modding my ULT33069 dashboard to connect to HD Audio header. Unfortunately digikey does not have these jacks in stock, so I will be using slightly different approach. I have some spare micro switches (pulled from old floppy and dvd drives). They have 3 mm prong that works as "button". So, I am going to simply glue them to the back of the existing jacks so that this prong enters through existing hole right where the tip of the inserted plug stops. Then I'll add one wire from Sense-Send (pin 7) to these switches and use existing 2 wires (pins 6 and 10) as Sense-Return 1 and 2. As simple as that.

The only thing that I haven't figured out yet is what to do with Presence# (pin 4). Intel specification requires 1k resistor to the ground. Yet Realtek datasheet for ALC889 codec shows simple shunt to the ground. I don't want to add another wire, or hung resistor on the connector, so ideally it would be just a short wire between pins 2 and 4 on the connector.
January 17, 2009 2:32:02 PM

@wwwoholic

Thanks for the tip on the connectors. The 3566AN is perfect and would almost drop in. Cut a few traces and drill the extra holes out - jumper to the header pins and now it's HD instead of AC. Simple. Maybe 20 minutes of work.

I did pull out the dongle (board) and I guess Ultra, in their infinite wisdom, or to save $1.25 didn't implement the EMI circuitry specified in the 'AC97 spec which is the same in the HD Audio spec. It would take a fair amount of work (and parts hanging off the board) to do this so I hope things work out without. Maybe a daughterboard made from Radio Shack parts would work. Need 4 inductors (800 Ohms at 100Mhz) and 4 100pf caps.

Presence# detects if the dongle is attached. On page 80 of the ALC889 datasheet presence# is tied to +3.3V via a 10K resistor and GPI to South Bridge. The 1K resistor would probably be for current limiting to prevent damage to the South Bridge.

Instead of just a jumper between 2 & 4, put the resistor between 2 & 4 but wrap it in heatshrink tubing. A very small (1/8 watt or smaller if you can find it) would probably be fine. I'm glad you pointed that out.

Regards,
David
January 17, 2009 2:56:38 PM

David,

what's interesting, is that I own several different Ultra boards and all of them except this one have EMI circuits. Well... I might just pull out the caps and inductors from one of those to save the trip to the store.

At 3.3V and 10K pull-up, we are talking about 30uA difference in current... nothing to worry about. Having said that I already put in 1K resistor in shrink wrap just as you suggesting. And my glued on micro switches work wonderful without any hassle of getting specialized jacks.

My overall conclusion is that about any AC97 dongle can be easily converted to true HD Audio. It's a wonder that thousands of hits on the web all point to useless threads ending up with "read the manual" or, in best cases, with "just plug AC connector and disable HD in BIOS" suggestions.

EDIT:

There might be an error in digikey description, since CUI product numbers generally contain diameter in them. SJ-635X series are 6.4 mm jacks and they do have isolated switches, like SJ-6356 for example.
January 17, 2009 3:52:47 PM

wwwoholic said:

At 3.3V and 10K pull-up, we are talking about 30uA difference in current... nothing to talk about.


I didn't even think to do the math.
wwwoholic said:

My overall conclusion is that about any AC97 dongle can be easily converted to true HD Audio. It's a wonder that thousands of hits on the web all point to usless threads ending up with "read the manual" or, in best cases, with "just plug AC connector and disable HD in BIOS" suggestions.


I had the same frustration. It saddens me that people aren't willing to dig in and solve the actual problem.

I looked through Switchcraft, Kobiconn and Kycon's offerings also and found nothing to match the CUI part. Your idea with the switch sounds the best & fastest option.
December 20, 2009 11:32:53 PM

hey guys, according to figure 6 on page 25 of the file , shouldn't the PRESENCE# pin (pin 4) be connected to the arrow wires in EMI filter. Their arrow tips look the same, just like the arrow tips of the ground pin (pin 2) and the ground of the jacks. The wires coming out from between the 220pF capacitors, should'nt they be connected to the PRESENCE# pin (pin 4) with the 1kΩ resistor?
Please reply.

Bini Man
December 21, 2009 4:39:07 AM

Bini Man said:
should'nt they be connected to the PRESENCE# pin (pin 4) with the 1kΩ resistor?Bini Man


Umm... yes and no.

Let's say 2 pins of microchip connected to each other and nothing else. Then they are "connected". Now, lets say they both connected to the common ground wire. Are they "connected"? Electrically - yes, they are. Logically, no engineer in a world would say that. Instead they would say that both are "grounded".

That "arrow" you are speaking of is a symbol for "ground". It is used to simplify the drawing by removing extra lines. Everything on a circuit that has arrow is connected together. If it makes it simpler for you, you can just remove all arrows and draw a wire connection between all of them.

In this particular case, outer contacts of the jacks, middle points between capacitors, pin 2 on the connector and one side of 1k resistor should be connected to each other.

Usually there is a black wire going from connector to the dash board that carries ground. You can put 1k resistor on the connector side between pins 2 and 4. Alternatively you can add one more wire from pin 4 to the dash board and place resistor there, connecting it between this new wire and any ground point of the printed circuit.
December 21, 2009 8:47:54 AM

Thanks alot for the reply. I'll try to do this connection. Just one question has anybody tried making the front panel cable and tested it? Just to know if it's safe and confirmed unharmful to the mb.
Thanks for the reply.
December 26, 2009 11:20:06 PM

Bini Man said:
Just one question has anybody tried making the front panel cable and tested it? Just to know if it's safe and confirmed unharmful to the mb.
Thanks for the reply.


I did not "make cable" per se. I modified existing Ultra dashboard to conform to HD standard. The modification consisted of adding additional wire to the existing cable, adding 1k presence resistor, adding two microswitches and cutting some PCB traces. The resulting device schematics was exactly as in that document you saw. It works perfectly now in two computers.

Now, is it safe? Well, I was confident enough in my work to try. That is not to say that it is safe to plug anything into your MB, because it isn't. So, in the end it is up to you. If you follow schematics exactly then it should work. If you make a mistake, well, no guarantee here.
!