Dragonboard 410c audio jack


For 3, is this a hardware limitation? Or software?


Two points;

FWIW, that microphone spec page says "Standard Operation Voltage: 4.5V Operation Voltage: 1.0V-10V.DC"
I.e., 4.5 is standard, but will work within the range of 1-10 volt. So… it should actually work, since 1.0 < 1.7 < 10.0. Right?

In any case, I was pointing out that microphone more an example of the type than of a specific model.

As far as the i2s goes, this point still requires clarification. The way the manual is laid out suggests that the “B” actually applies to MI2S. Actually, it more than suggests it, it actually states that the MI2S is bi-directional.

For instance, pin E40 shows “B-PD:nppukp --> configurable I/O”, "B --> MI2S #1 serial data channel 0"
pin E38 shows “B-PD:nppukp --> configurable I/O”, “DI --> gyro interrupt”, and “B --> MI2S #1 serial data channel 1”.

That makes it pretty clear that the “B” applies specifically to MI2S, just as the “DI” applies specifically to gyro interrupt (which is obviously an input only), and the B-PD:nppukp applies specifically to configurable I/O (Bidirectional digital, default pull-down programmable no-pull, pull-up, or keeper).

If the I2S data pins were output only, they should be labeled “DO”.

So… either the manual is incorrect, or there is some way to set those MI2S data pins as input. If that means diving into the deepest recesses of the kernel, that’s fine, I just need a kick in the right direction.


About the GM1 microphone pad on the bottom… looks like that microphone is essentially a “three wire” type microphone (ground, bias, output). The pad lower-right closest the “GM1” label is pin 4, output. I should be able to treat that pin the same as mic3. Without testing, I’m assuming that pin1 supplies the same 1.7 bias as everywhere else, but doesn’t really matter since I won’t be using it…

Those pads are pretty big from my experience. Will be no problem tying into pin 4, which is the only one I need.

So mic1+mic3 = stereo line in, mic2 is pre-biased and good for an actual 2-wire microphone.

I’d still like to get to the bottom of this i2s thing though.


ljking, you mention CMA-6542TF-K being a good microphone for MIC2. Does the PM8916 handle the resistor and capacitor internally or do we need to provide that externally?

Datasheet: http://www.cui.com/product/resource/cma-6542tf-k.pdf

CDC_MIC2_P provides the reference voltage…and I assume GND_CFILT is the ground…but that doesn’t work so I’m wondering if the external components are necessary.

I can see from the debug messages that it is selecting the “headset-mic” profile:

D/audio_hw_primary: select_devices: out_snd_device(0: ) in_snd_device(43: headset-mic)

Which I have defined in mixer_paths_sbc.xml as the default:

&lt;path name="headset-mic"&gt;
    &lt;path name="adc2" /&gt;
    &lt;ctl name="ADC2 MUX" value="INP2" /&gt;
    &lt;ctl name="IIR1 INP1 MUX" value="DEC1" /&gt;

But all I get is buzzing when I record audio.



Hai Andrewn,
How did you defined these settings as default in mixer_paths_sbc.xml
<path name=”headset-mic”>
<path name=”adc2″ />
<ctl name=”ADC2 MUX” value=”INP2″ />
<ctl name=”IIR1 INP1 MUX” value=”DEC1″ />

There are lots of setting and also for HDMI, How to configure the “default settings” (for headset-mic). Have you tested Speaker and headset.

Because am having issue in headset. This is the thread which i have started https://www.96boards.org/forums/topic/audio-headset-issue/


This comment is right on the money. I actually tried this out. Once you have Mic1 and Mic3 connected (Mic1 has to be soldered on DB410c or blue wired). The commands listed in this post should help :


I was looking for USB audio input solution but I could not get any. Would you please share your solution or some related article.