void setup()  {
    // put your setup code here, to run once:
    Serial. begin(115200) ;
    if(!Serial) Serial. println("serial is not ok") ;
    pinMode(16, OUTPUT);

}

void loop() {
 // put your main code here, to run repeatedly:
digitalWrite(16, HIGH);
Serial.println("green is on");
delay(5000);
digitalWrite(16, LOW);
Serial.println("green is off");
delay(5000);
}