Audio In

The Audio Output should be verified to work before attempting the audio input tests in this section.

Carrier Board	Audio In	Audio Out
COM Carrier Board V1	No audio connectors	Headphone jack
COM Carrier Board V2	Microphone jack and Line In jack	Headphone jack and Line Out jack
uCOM Carrier Board V3	No audio connectors	No audio connectors

U-Boot

Audio in is currently not supported in U-Boot.

Linux

As described it the Audio Out section it is possible to see all the audio mixer controls.

amixer controls

numid=2,iface=MIXER,name='Master Playback ZC Switch'
numid=1,iface=MIXER,name='Master Playback Volume'
numid=4,iface=MIXER,name='Line Capture Switch'
numid=5,iface=MIXER,name='Mic Boost Volume'
numid=6,iface=MIXER,name='Mic Capture Switch'
numid=8,iface=MIXER,name='ADC High Pass Filter Switch'
numid=3,iface=MIXER,name='Capture Volume'
numid=10,iface=MIXER,name='Playback Deemphasis Switch'
numid=11,iface=MIXER,name='Input Mux'
numid=14,iface=MIXER,name='Output Mixer HiFi Playback Switch'
numid=12,iface=MIXER,name='Output Mixer Line Bypass Switch'
numid=13,iface=MIXER,name='Output Mixer Mic Sidetone Switch'
numid=7,iface=MIXER,name='Sidetone Playback Volume'
numid=9,iface=MIXER,name='Store DC Offset Switch'

Line Bypass

The audio codec on the COM Carrier Board V2 can be put into Line Bypass mode which connects Line In with Line Out. To test this connect an audio source (e.g. phone or PC) to the Line In jack and connect speakers to the Line Out jack.

To start the Line Bypass.

amixer -q cset numid=11 on

To stop the Line Bypass.

amixer -q cset numid=11 off

Audio Recording

Another way to test audio is to record from the microphone and then play it back.

Enable microphone.

amixer -q cset numid=14 Mic
amixer -q cset numid=6 on

Record 5 seconds in CD quality.

arecord -d 5 -fcd myfile.wav

Disable microphone.

amixer -q cset numid=6 off

Play recorded audio.

aplay myfile.wav

If you don't hear any audio check the settings in the Audio Out section.