#include <Wire.h> 
#include <Adafruit_PWMServoDriver.h>

#define PCA9685_ADDRESS  0x40 
Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(PCA9685_ADDRESS);

void setup() {
  pwm.begin();  
  pwm.setPWMFreq(500);  
}

void loop() {
  pwm.setPWM(0, 0, 4000);
  digitalWrite(8, HIGH);  
  delay(200); 
  pwm.setPWM(0, 0, 0);  
  digitalWrite(8, LOW);  
  delay(200); 
}