[Gta04-owner] Sound devices in the GTA04

Neil Jerram neil at ossau.homelinux.net
Sun Dec 30 13:35:44 CET 2012

Hi Neil and Nikolaus,

I've been looking at / checking the ALSA states in QtMoko, after
discovering that the PhoneHeadset state doesn't yet work.  Although it's
nearly a year old, I think your exchange beginning with the mail below
is the best reference for understanding the ALSA controls, and I have a
few questions about the details.

I've also attached a spreadsheet that shows the current QtMoko A3 state
settings, with markup about which states are or are not basically
working, and whether controls are relevant to capture or playback, or
irrelevant to the GTA04.

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This might be useful to show the context for my questions - and of
course I'd appreciate any comments you have on it.

NeilBrown <neilb at suse.de> writes:

> The best starting point is the diagram on page 692 of the doco for
> TPS65950 aka TWL4030 referenced in table 5.1 of the GTA04 manual.


> It is figure 14-6.  It displays "Option 1".  "Option 2" doesn't make sense for
> the GTA04A3 due to the connections available.
> There are 2 input channels, 'left' and 'right'.
> 'left' can be connected to:
>   - on-board microphone                                 "Analog Left Main Mic"
>   - headset microphone                                  "Analog Left Headset Mic"
>   - AUX input line on alternate cable in headset jack   "Analog Left AUXL"
> 'right' can be connected to
>   - AUX input line on alternate cable in headset jack   "Analog Right AUXR"

I assume the controls for selecting these are:
-  'Analog Right Sub Mic Capture Switch'
-  'Analog Right AUXR Capture Switch'
-  'Analog Left Main Mic Capture Switch'
-  'Analog Left Headset Mic Capture Switch'
-  'Analog Left AUXL Capture Switch'
-  'Analog Left Carkit Mic Capture Switch'

Does the "Sub Mic" have any meaning in the GTA04?

> Both channels have adjustable gain:  "Analog"
> (For these to be accessable "TX1" and "TX2" must be set to "Analog" - we
> should try to impose that in the kernel and hide those settings).

What are the 3.5 controls for the gain?  The ones that look likely to me
-  'TX1 Digital Capture Volume'
-  'TX2 Digital Capture Volume'
-  'Analog Capture Volume'
-  'TX2 Capture Route'
-  'TX1 Capture Route'

But there's nothing in those names about left and right.

-  Do the "1" and "2" in "TXn" correspond to left and right?

-  Does 'Analog Capture Volume' apply to both left and right input

> The output side is a bit more complex.  There are 4 digital channels allowing
> quadraphonic sound!  Left and Right, Front and Back.  They can be mixed in
> various ways with each other and with the amplified input streams and sent to
> various output devices.

I haven't gone deeply into the playback side yet, except that I've
wondered a bit about sidetone.  The Wikipedia entry indicates that
sidetone is probably desirable, but I'm not completely clear about which
ALSA controls to use to get it.

> The 4 amplified analogue signals are optionally mixed with either the left or
> right input channel (to provide a Voice Side-tone) in the main amplifier
> stage.  These are controlled by the switches
>    "Left1 Analog Loopback", "Right1 Analog Loopback"
>    "Left2 Analog Loopback", "Right2 Analog Loopback".
> There is then a 5th analogue amplifier which just takes the Voice Loopback
> (sidetone) signal and amplifies it separately to the digitally provided
> signals.

So is "Voice" just "Left input + Right input"?  If it is, how do the
"Voice" controls provide any further flexibility on top of the "Left"
and "Right" loopback controls?

Finally, do you know if the "Downlink" controls have any relevance to
sidetone?  Or are they to do with something that isn't hooked up in the

> Oh, and "Happy new year" and all that.

And to you too!

Many thanks,

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