//www.elegoo.com //2016.09.12 int LED=13;//Define 13 pin for LED volatile int state = LOW;//The initial state of the function is defined as a low level char getstr; //Defines a function that receives the Bluetooth character void setup() { pinMode(LED, OUTPUT); Serial.begin(9600); } /*Control LED sub function*/ void stateChange() { state = !state; digitalWrite(LED, state); } void loop() { getstr=Serial.read();//The Bluetooth serial port to receive the data in the function if(getstr=='A'){ stateChange(); } }