Arduino frequency counter

I needed a frequency counter with serial output so an Arduino can count and process, then I realized that the Arduino can be used directly for counting in the range 0 to 8Mhz.
Code and lib is from this reference: http://interface.khm.de/index.php/lab/interfaces-advanced/arduino-frequency-counter-library/

Here's the diagram:

 The oscillator part (on the left) was just for testing if was working, if standalone input is "F_in" on diagram.
The serial out from the Arduino looks like this:

The input signal on D5 of the "Nano":

...and as curiosity the signal on the oscillator:

...not the most beautiful but enough for testing.

Code is this one:
 // ----------------
 #include
// counter code from here: http://interface.khm.de/index.php/lab/interfaces-advanced/arduino-frequency-counter-library/

unsigned long frq;

void setup() {
  Serial.begin(9600);        // connect to the serial port
  Serial.println("Starting");
}

void loop() {
  FreqCounter::f_comp=10;   // Cal Value / Calibrate with professional Freq Counter
  FreqCounter::start(100);  // 100 ms Gate Time
  while (FreqCounter::f_ready == 0)
  frq=FreqCounter::f_freq;
  Serial.print("  F: ");
  Serial.println(frq);
  delay(20);
} 
 //-----------------


Things changed, don't need this part/project any more, in any case it stays for future reference.

Have a nice week!