Frequency

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#1

Hello!

I need to get the frequency that I send to arduino from my computer by jack (a mic connects mi pc to arduino). For example, if I send 1000Hz, Arduino have to catch 1000Hz.

Are there any code done?

Tnx!!

#2

Goertzel's algorithm?
FFT?

#3

But how can I use it?
Are there examples that process the sound and obtain the frequency? I need only that

#4

Digital signal processing is not that easy. However, if you can find an FFT library you won't have to write the hard part of the code yourself.

[u]FFT/DFT[/u] will give you the frequency components and their amplitude at any point/period of time.

If you have a pure tone or a pure square wave, you can simply measure the time between zero-crossings* (or between rising-edges) and calculate the frequency. (Real-world natural sounds contain more than one frequency so this may, or may not, work for finding the "fundamental" frequency.)

  • Since the Arduino cannot accept the negative half of an audio/AC waveform, you have to add bias or otherwise deal with the negative signal, and then find the true zero-crossing or find a point near the zero crossing in software.
#5

what frequency resolution do you need, and is the incoming signal a pure tone?

#6

I am not an arduino programmer, only need the code that works :smiley:

I'm sure you've got information or code that works and do that, I'll put the code and don't matter how works, only the result

Any interesting link?

#7

I’ve got this code, but it only displays strange characters:

#define LOG_OUT 1 // use the log output function
   #define FHT_N 256 // set to 256 point fht
   
   #include <FHT.h> // include the library
   
   void setup() {
     Serial.begin(9600); // use the serial port
     TIMSK0 = 0; // turn off timer0 for lower jitter
     ADCSRA = 0xe5; // set the adc to free running mode
     ADMUX = 0x40; // use adc0
     DIDR0 = 0x01; // turn off the digital input for adc0
  }
   
   void loop() {
     while(1) { // reduces jitter
       cli();  // UDRE interrupt slows this way down on arduino1.0
      for (int i = 0 ; i < FHT_N ; i++) { // save 256 samples
         while(!(ADCSRA & 0x10)); // wait for adc to be ready
         ADCSRA = 0xf5; // restart adc
         byte m = ADCL; // fetch adc data
         byte j = ADCH;
         int k = (j << 8) | m; // form into an int
        k -= 0x0200; // form into a signed int
         k <<= 6; // form into a 16b signed int
         fht_input[i] = k; // put real data into bins
       }
       fht_window(); // window the data for better frequency response
      fht_reorder(); // reorder the data before doing the fht
      fht_run(); // process the data in the fht
       fht_mag_log(); // take the output of the fht
       sei();
       Serial.write(255); // send a start byte
       Serial.write(fht_log_out, FHT_N/2); // send out the data
       Serial.println(long);
     }
   }

How can I display the frequency?

#8

it only displays strange characters:

Did you set the correct bit rate?

#9

yeah, I think the problem is "write" instead of "print", but I don't know how to change becouse it's an array.

But the main problem is display the frequency, because "fht_log_out" is an array and I read that I have to get the picks

How can I do that?

#10

http://forum.arduino.cc/index.php?topic=179095.0

Pete

#11

I've got a new problem

I'd like to read in a digital port instead of analog port.

With the code above, how can I do this?

#12

Scrub all the ADC code, and do a digitalWrite at approximately the same interval.
You'll probably want to scale up any ones read to a more sensible value for the FFT.

#13