feeding audio into arduino

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

I am trying to feed an audio signal into arduino. I am aware that I have to add a bias in order to make the signal all positive.

I have checked many sites but nothing seems to work ...

well I have to admit that I am an absolute beginner in electronic so I wonder if there is a "breadboard" schematics for dummies somewhere for solving my problem

thanks in advance

yodboy

2

First one might ask what are you planning to do with the audio signal once it is avalible to your Arduino? Getting the whole picture might aid in how best to meet your program objective.

Lefty

3

Where the audio signal is coming from is an important piece of information, too. Microphone? MP3 player? Something else?

How do you know that nothing has worked? What code are you running on the Arduino to process the incoming signal?

4

I've made a simple oscillator based on arduino with a pot controlling the rate of the oscillator.

Then I fed the output of the LFO from a nord-micro modular into arduino through an analogRead() . By simply adding the values from the analogRead to the rate I was able to modulate the frequency of the signal from the oscillator (...trivial , I know ... but fun ... ). I realized that the LFO from the micromodular is bipolar and arduino cannot read negative voltage. So half of the wave from the LFO is not used to modulate the oscillator.
My idea was to add a constant value to the LFO wave in order to obtain an only positive wave (ie: instead of a wave oscillating between -3 and +3 volts I would like to have a wave oscillating in the range 0 volts to +6).

Once I get it I think it would be easy to manipulate the LFO signal by the software (adding it to the base frequency etc... etc ...)

I have tryed to make the circuit like these:
http://www.element-14.com/community/message/17480

http://masteringelectronicsdesign.com/bipolar-to-unipolar-converter-examples/

http://afrotechmods.com/forums/index.php?topic=8335.0

But nothing seems to work. I still have a bipolar signal on the oscilloscope.

To be honest my ability to read schematics needs to be improved (working on it) for this reason I asked for some kind of "rosetta" pict of a breadboard with a circuit for feeding audio into arduino

thanks again for your help
yodboy

5

I apologize for the poor information about what I am trying to do.
so please allow me to post again my request.

I have made a simple oscillator using the code below:

int CV_mod; 
int potval;
void setup() {
  Serial.begin(9600);
  pinMode(9, OUTPUT);      
}

void loop()
{
  while(1){
    CV_mod=analogRead(2)*3;
    if (CV_mod==0){
    CV_mod=1;
    }
    potval=analogRead(0);
    digitalWrite(9, HIGH);
    delayMicroseconds(12*potval*CV_mod);
    digitalWrite(9, LOW);
    Serial.println(potval);
  }
}

I would like to modulate the rate of the oscillator using an external source like the LFO of a nord modular.

To do this I fed the output of the modular into arduino by the analogRead of pin #2 and I stored the value into the variable CV_mod.

The picture below shows the wave obtained from arduino without any modulation :

825×316 41.9 KB

and here with the modulation:

825×316 41.8 KB

Then I realized that arduino doesn't read the negative voltage and indeed as I feed a sine LFO like this:

825×316 41.1 KB

coping the values of the CV_mod variable from the arduino monitor I obtained this:

838×391 19.4 KB

ok in the last picture, I think that, because of the Nyquist theorem, I didn't obtain a faithful representation of the sine-LFO fed into arduino.

But it also looks like half of the sine wave is missing.

So what I trying to do is to "add" a costant value to the LFO signal before to feed it into arduino. In this way I should be able to keep the complete shape of the wave.

thanks again

yodboy

6