1

   1 /*
   2 fft_adc.pde
   3 guest openmusiclabs.com 8.18.12
   4 example sketch for testing the fft library.
   5 it takes in data on ADC0 (Analog0) and processes them
   6 with the fft. the data is sent out over the serial
   7 port at 115.2kb.  there is a pure data patch for
   8 visualizing the data.
   9 */
  10 
  11 // do #defines BEFORE #includes
  12 #define LOG_OUT 1 // use the log output function
  13 #define FFT_N 256 // set to 256 point fft
  14 
  15 #include <FFT.h> // include the library
  16 
  17 void setup() {
  18   Serial.begin(115200); // use the serial port
  19   TIMSK0 = 0; // turn off timer0 for lower jitter - delay() and millis() killed
  20   ADCSRA = 0xe5; // set the adc to free running mode
  21   ADMUX = 0x40; // use adc0
  22   DIDR0 = 0x01; // turn off the digital input for adc0
  23 }
  24 
  25 void loop() {
  26   while(1) { // reduces jitter
  27     cli();  // UDRE interrupt slows this way down on arduino1.0
  28     for (int i = 0 ; i < 512 ; i += 2) { // save 256 samples
  29       while(!(ADCSRA & 0x10)); // wait for adc to be ready
  30       ADCSRA = 0xf5; // restart adc
  31       byte m = ADCL; // fetch adc data
  32       byte j = ADCH;
  33       int k = (j << 8) | m; // form into an int
  34       k -= 0x0200; // form into a signed int
  35       k <<= 6; // form into a 16b signed int
  36       fft_input[i] = k; // put real data into even bins
  37       fft_input[i+1] = 0; // set odd bins to 0
  38     }
  39     // window data, then reorder, then run, then take output
  40     fft_window(); // window the data for better frequency response
  41     fft_reorder(); // reorder the data before doing the fft
  42     fft_run(); // process the data in the fft
  43     fft_mag_log(); // take the output of the fft
  44     sei(); // turn interrupts back on
  45     Serial.write(255); // send a start byte
  46     Serial.write(fft_log_out, 128); // send out the data
  47   }
  48 }
  49