Microphone BIAS Voltage not working on Orin AGX Development Kit

We followed the guide in this post:

After flashing again, we effectively get sound in the headphone’s pins, but the microphone input doesn’t work. If I directly input audio from a source, it works without problem, but the capacitor-based microphones don’t work.

According to this schematic, the MICBIAS should output the voltage that polarizes the microphone, but there is no voltage in the mic pins:

How do I enable that BIAS voltage?

I found this post:

But we don’t actually know where to do the change, or which file to edit.

Hi Camilo2,

If you are referring to this comment, the edit needs to be done in sound node of kernel DT file.

I suppose that you are using AGX Orin. https://tegra-sw-opengrok.nvidia.com/source/xref/rel-35_l4t/hardware/nvidia/platform/t23x/concord/kernel-dts/cvb/tegra234-p3737-audio.dtsi is the relevant file to add the MICBIAS route mentioned in earlier comment

But earlier comment is relevant to JP 4.x. If you are using JP 5.x, the MICBIAS route needs to added as per Audio Setup and Development — Jetson Linux<br/>Developer Guide 34.1 documentation


Hi atalambedu,

We have the same issue on Jetson AGX Orin Dev-Kit Module (P3701-0000) with Jetson AGX Orin reference carrier board (P3737-0000). using L4T R35.2.1.

The microphone is not working, and MIC_IN_DETECT continuously detects the MIC jack is in, even if I unplug the Audio Panel header cable or unplug the MIC jack.

So the Ubuntu desktop/Settings/Sound still presents an Input Device, “Analog Input - Built-in Audio.”

The files https://tegra-sw-opengrok.nvidia.com/source/xref/rel-35_l4t/hardware/nvidia/platform/t23x/concord/kernel-dts/cvb/tegra234-p3737-audio.dtsi can not access.

Can you provide it again?

Hi atalambedu,

We reflash the R35.2.1 or R35.3.1 official Jetson Linux release package and sample file system again.

The Analog MIC becomes normal.

Hi indy.lin,

So do you mean the continuous detection issue is resolved with reflash?


Hi atalambedu,

I mean, analog MIC can record normal sound with reflash AGX Orin Dev-Kit.

Reference HDA front panel connection and P3737_A04_OrCAD_schematics.

We measure HDA Pin level:

HDA Pin Define No front panel Front panel in HP IN MIC IN HP IN & MIC IN
4 Detect front panel 1.8V 1.8V 0V 1.8V 0V
6 Short to 7 when MIC plugin 0.9V 0.9V 0.9V 0V 0V
7 Sense common pin 0V 0V 0V 0V 0V
10 Short to 7 when HP plugin 0.9V 0.9V 0V 0.9V 0V

MIC_IN_DETECT(AUDIO_MIC_HDA) pin(6) and HP_JACK_DETECT(AUDIO_HP_HDA) pin(10) level should be 1.8V with jack unplug.

PRESENCE#(AUDIO_PRDNT_HDA_L) pin(4) level should be 0V with the Front panel in.

But Ubuntu desktop/Settings/Sound always presents an Input Device, “Analog Input - Built-in Audio” and an Output Device, “Analog Output - Built-in Audio”, even I unplug the HP jack and MIC jack.

The HP/MIC jack plug/unplug event is not working.

Hi indy.lin,

Sorry for the late reply.

“Analog Input - Built-in Audio” and “Analog Output - Built-in Audio" entry is for Sound card 0. It is tied with many other audio I/O’s. So it presence or absence cannot be correlated with Jack State. It will appear even if Jack is unplugged

If you need to check the jack insertion state, you could use below mixer control to check the same,

amixer -c 1 cget name="CVB-RT Jack State"


Hi atalambedu,

Sorry for the late reply.

I overlooked the APE sound card that has bonded with other ADMAIFs.

The name=“CVB-RT Jack State” mixer control can detect jack insertion state.

Thanks for your kind support.

My pleasure! Will mark the issue for closure