Line In Audio Recording with LIME2-SHIELD

Started by tyldan, January 11, 2021, 06:08:24 pm

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tyldan

I am trying to record audio with LIME2-SHIELD + A20-OLinuXino-LIME2.

I have connected a simple analog Microphone, using `arecord` everything looks fine except the generated audio files have no sound. Trying to use a vumeter also shows nothing gets in.

```
# amixer -c 0 scontrols
Simple mixer control 'FM',0
Simple mixer control 'Line',0
Simple mixer control 'Line Boost',0
Simple mixer control 'Mic',0
Simple mixer control 'Mic1',0
Simple mixer control 'Mic1 Boost',0
Simple mixer control 'Mic2',0
Simple mixer control 'Mic2 Boost',0
Simple mixer control 'Left Mixer Left DAC',0
Simple mixer control 'Power Amplifier',0
Simple mixer control 'Power Amplifier DAC',0
Simple mixer control 'Power Amplifier Mixer',0
Simple mixer control 'Power Amplifier Mute',0
Simple mixer control 'Right Mixer Left DAC',0
Simple mixer control 'Right Mixer Right DAC',0
```

I thought maybe the capture device is muted, it seems that there is no control with 'capture' capabilities.

```
# amixer -c 0 sget FM
Simple mixer control 'FM',0
  Capabilities: pvolume pvolume-joined pswitch
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 3
  Mono:
  Front Left: Playback 3 [100%] [0.00dB] [off]
  Front Right: Playback 3 [100%] [0.00dB] [off]

# amixer -c 0 sget Mic
Simple mixer control 'Mic',0
  Capabilities: pvolume pvolume-joined
  Playback channels: Mono
  Limits: Playback 0 - 7
  Mono: Playback 7 [100%] [6.00dB]
```

What am I doing wrong?

tyldan

Got reply from Olimex support:

"...the big thing here is that the naming
of connectors is a bit misleading. The connector that you used, is named
"Audio_IN", but by default it is actually set to "Line In", in order to
set it for "Mic In" operation some hardware re-adjustments are required.
The other connector is named "Audio_OUT" but it is 4-conductor TRRS
combo connector (for headphones and microphone combo set) - it can also
be used to connect 3-conductor headphones but it won't work with
3-conductor microphone.

So it is probably incompatibility between the board's jack that you used
and the microphone."