Capture sound from microphone

Started by Subzero, September 20, 2012, 09:40:13 AM

Previous topic - Next topic

Subzero

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

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

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

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

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