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 #define LOG_OUT 1 // use the log output function
  12 #define FFT_N 256 // set to 256 point fft
  13 
  14 #include <FFT.h> // include the library
  15 
  16 void setup() {
  17   Serial.begin(115200); // use the serial port
  18   TIMSK0 = 0; // turn off timer0 for lower jitter
  19   ADCSRA = 0xe5; // set the adc to free running mode
  20   ADMUX = 0x40; // use adc0
  21   DIDR0 = 0x01; // turn off the digital input for adc0
  22 }
  23 
  24 void loop() {
  25   while(1) { // reduces jitter
  26     cli();  // UDRE interrupt slows this way down on arduino1.0
  27     for (int i = 0 ; i < 512 ; i += 2) { // save 256 samples
  28       while(!(ADCSRA & 0x10)); // wait for adc to be ready
  29       ADCSRA = 0xf5; // restart adc
  30       byte m = ADCL; // fetch adc data
  31       byte j = ADCH;
  32       int k = (j << 8) | m; // form into an int
  33       k -= 0x0200; // form into a signed int
  34       k <<= 6; // form into a 16b signed int
  35       fft_input[i] = k; // put real data into even bins
  36       fft_input[i+1] = 0; // set odd bins to 0
  37     }
  38     fft_window(); // window the data for better frequency response
  39     fft_reorder(); // reorder the data before doing the fft
  40     fft_run(); // process the data in the fft
  41     fft_mag_log(); // take the output of the fft
  42     sei();
  43     Serial.write(255); // send a start byte
  44     Serial.write(fft_log_out, 128); // send out the data
  45   }
  46 }
  47