AudioIn

Some Overo expansion boards provide a standard Audio Out and an Audio Line-in. Without a pre-amplifier, plugging a microphone into this Line-In port just won't work.

To use a microphone with the Overo, connect a microphone to the Mic-in lines available on the Overo connectors (and broken out on the pin headers of some boards). In addition, you need to be using a kernel that is more recent that 25 Sept. 2010 (see here for recent pre-built images.

Capture Interface Settings

The audio Line-in uses the 'Analog Right AUXR' and the 'Analog Left AUXL' lines; the Mic-in uses the 'Analog Left Main Mic' and the 'Analog Right Sub Mic' lines. Use amixer or alsamixer to select the correct capture interface for your application.

Currently, Line-in is selected as the default capture interface. You could switch to the Mic-in interface like this:

$ amixer -c 0 sset 'Analog Right AUXR' nocap
$ amixer -c 0 sset 'Analog Left AUXL' nocap
$ amixer -c 0 sset 'Analog Left Main Mic' cap
$ amixer -c 0 sset 'Analog Right Sub Mic' cap

To test, you might use something like this; it records for two seconds and then plays back the recorded sound.

$ arecord -d 2 -f cd -t wav foobar.wav;aplay foobar.wav