Neopixel with Firmata

Hello, I'm trying to modify Firmata to use the Adafruit Neopixel library. Presently nothing works, any pixel does't light up any color.
What am I doing wrong?

#include <Adafruit_NeoPixel.h>

#include <Firmata.h>


#define PIN            6
// How many NeoPixels are attached to the Arduino?
#define NUMPIXELS      16
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

//void sysexCallbackFunction(byte pin, byte byteCount, byte *arrayPointer);

void sysexCallback(byte num, byte argc, byte *argv)
{
  pixels.begin();
  pixels.setPixelColor(num, pixels.Color(argc, argv[0], argv[1]));
}

void setup() {
  // put your setup code here, to run once:
  Firmata.setFirmwareVersion(FIRMATA_MAJOR_VERSION, FIRMATA_MINOR_VERSION);
  Firmata.attach(START_SYSEX, sysexCallback);
  Firmata.begin();
}

void loop() {
  // put your main code here, to run repeatedly:
  while (Firmata.available()) {
    Firmata.processInput();
  }
}

Presently nothing works

Not even the standard Firmata functionality?

How are you trying to cause the sysexCallback() to be executed? Do you have any idea whether it is being invoked?

Why are you calling the begin() method in the callback? Shouldn't that be in setup()?

oh i totaly dont understand how that should work