Recording audio on M3+KF on AGL 6.0

Hello,

I'm looking into audio recording (to ultimately support voice commands) on an M3 with Kingfisher.  I'm trying to learn how 4A works, but haven't seen much about microphones, line in, or recording.  And initially, I'm just trying to get any input using command line tools like arecord, parec, etc.  However, I'm not having any luck.  

If I do "arecord -l", I see many devices listed (see below), with the device hw:2,0 ak4613 being most likely (to use the mic port on the M3 board).

But when I try:

arecord -D hw:2,0 -f S24_LE -c 2 -r 48000

it generates data, but all zeros.  

I've tried the other devices as well, and they either record null data or fail due to device open or device missing.

How can I record data on AGL 6 with 4A?  And are there any sample apps that record microphone input?

thanks

Jason Reich.

A full list of alsa recording devices on my system: