I’m working on a project that requires me to take an input (3.5mm headphone jack) and split it into 7 frequency bands. I then want those 7 frequency bands to give me a number (0-255 for example) to be able to control various lighting and moving effects that my project requires. The project will be run off of an Arduino Mega 2560.

I can handle how to work with the numbers once I get 7 variables outputting from 0-255 for example but I need to get to that point. So far I’ve taken several hours trying to work with various examples of FFT code to create a VU however I can’t figure out how to get the readout from FFT into the form I want.

This is the example code I found that I’ve been toying with in attempts to be able to do what I want:

```
#define LOG_OUT 1 // use the log output function
#define FFT_N 256 // set to 256 point fft
#include <FFT.h>
void setup() {
Serial.begin(115200); // use the serial port
TIMSK0 = 0; // turn off timer0 for lower jitter - delay() and millis() killed
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 < 512 ; i += 2) { // 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
fft_input[i] = k; // put real data into even bins
fft_input[i+1] = 0; // set odd bins to 0
}
// window data, then reorder, then run, then take output
fft_window(); // window the data for better frequency response
fft_reorder(); // reorder the data before doing the fft
fft_run(); // process the data in the fft
fft_mag_log(); // take the output of the fft
sei(); // turn interrupts back on
Serial.write(255); // send a start byte
Serial.write(fft_log_out, 16); // send out the data
}
}
```

I know this code by how it is written shows 16 bars and I also need help in changing that down to the appropriate 7.

The code also has known issues with the Serial.write functions but I just copied the original code here because I’m having issues getting down to the 7 variables so I can print my numbers.

Thanks,