Front Panel connectors - Intel HD Audio to AC97 (MSI P35 Antec Case)

Discussion in 'MSI' started by strommsarnac, Aug 11, 2007.

  1. strommsarnac

    strommsarnac Guest

    Use the following. Connect the case plugs to the designated pins on
    the mainboard.

    However, the autodetect doesn't work, but that's not a big deal for

    1. Mic Sig
    2. Gng
    3. Mic BIAS (power)
    4. empty
    5. FPOUT-R
    6. RET-R
    7. empty
    8. empty
    9. FPOUT-L
    10. RET-L

    I read somewhere else the RET-R/L are really optional
    strommsarnac, Aug 11, 2007
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  2. strommsarnac

    Horst Franke Guest

    Sorry *, but how should autodetect work on HW connections?
    There's no logic behind and resistance detection? (cannot believe in that)
    I think this is because, the RET = GROUND connection will have
    been established somewhere else.
    Horst Franke, Aug 12, 2007
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  3. strommsarnac

    Paul Guest

    One method of jack detection, is on PDF page 172, in the section entitled

    "7.4.2 Audio Jack Detection Circuits"

    Each of the switches shown in the diagram, is a "side contact" built into
    the jack.

    By using to of those four resistor circuits, it is possible to sense the
    state of up to eight jacks. Two of the jacks, would be the headphone and
    microphone jack, on the front of the computer case. The FP_AUDIO header
    has three pins, which presumably are tied to the resistor circuit.

    This is an example of a jack suitable for HDaudio. Contacts 4, 5, and 6 are
    an isolated switch, which does not contact the analog signals. Some part of
    contacts 4, 5, and 6, could be connected to the circuit shown on PDF page 172
    of the Intel standard. If you bought two of these jacks, and wired them to
    your FP_AUDIO 2x5 header, then you would have an HDaudio compatible solution.
    I am not aware of any computer cases that currently do that.

    Most computer cases, are not equipped with a jack such as the one above. Computer
    cases have no isolated switches for indicating that a plug is present in the
    jack. As a result, the switch based detection mechanism won't work.

    If the motherboard is HDaudio, then RET-L and RET-R should not be
    connected. The wires should be left floating. If the motherboard is an older
    model, with a real AC'97 CODEC, then RET-L and RET-R should be connected.

    There is a secondary jack detection method, which involves actually sensing
    if there is a load connected to the port. Details of the existence of such
    mechanisms, is poorly done in CODEC datasheets, and so this topic is hard
    to research. Presumably, the impedance sensing method must be an AC based one,
    because normally the jacks are AC coupled with capacitors. And the method must
    exist, because the sound drivers are capable of detecting that something has
    been plugged into the front of the computer.

    Paul, Aug 12, 2007
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