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Author Topic: Capture sound from microphone  (Read 4232 times)

Subzero

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Capture sound from microphone
« on: September 20, 2012, 09:40:13 AM »
I can't seem to find the proper setting in the mixer activate the microphone. Can anybody please help me figure this out?  I see the "Mic PGA" and I have volume turned up. But it doesn't seem to capture any sound.

Thanks in advance.

Mark

SencillamenteIvan

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Re: Capture sound from microphone
« Reply #1 on: September 20, 2012, 10:32:04 AM »
Good morning:
You've to set the capture input to ADC. Write this command : amixer sset "ADC" 100% cap
Remember that you need a resistor an capacitor to connect a mic.

Subzero

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Re: Capture sound from microphone
« Reply #2 on: September 21, 2012, 02:16:56 AM »
Thanks for the reply!!!

Forgive me, but I am completely new to this ARM hardware. 

So, I read that in order to use the microphone, it needs some bias voltage.  Which in turn requires the capacitor and resistor.  I found a schematic that talks about using the LRADC0 or 1 to provide the voltage from one of the pins. 

How does one accomplish this?

I found a regutil on the Chumby developement area that changes bits...Is there a comparable tool here.

I am using Debian right now.

Am I going to have to modify the hardware in order to use the Mic input?

Thanks again

Mark

SencillamenteIvan

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Re: Capture sound from microphone
« Reply #3 on: September 21, 2012, 11:34:13 AM »
Good morning:
Sorry I've a mistake. It's not pin 34 it's GPIO pin 36, (internal p34). See page 40 on the manual.
LRADC it's a simple 10 bit adc used for touchscreen, joysticks ,etc...

The most simple way to record sound is connecting directly a mic (positive to pin 36 and negative to ground).
You can bias it using a simple resistor an capacitor before ping 36, but you don't need to modify hardware.

In which application are you working on?

Subzero

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Re: Capture sound from microphone
« Reply #4 on: September 22, 2012, 05:28:16 AM »
Thanks again for the information.

I'm using the maxi as an interface to a ham radio for a Internet link to radio system called IRLP.

My only complaint so far is that the jack on board does not function as a microphone input. However, given the information you provided I can fire up another microphone input jack and connect it to pin 36

Mark