Gravity: RS485 IO Expansion Shield for Arduino (แท้จาก DFRobot)

int EN = 2; //RS485 has a enable/disable pin to transmit or receive data. Arduino Digital Pin 2 = Rx/Tx 'Enable'; High to Transmit, Low to Receive

void setup()
{
pinMode(EN, OUTPUT);
Serial.begin(19200);
}

void loop()
{
// send data
digitalWrite(EN, HIGH);//Enable data transmit
Serial.print('A');
delay(1000);
}

int ledPin = 13;
int EN = 2;
int val;

void setup()
{
pinMode(ledPin, OUTPUT);
pinMode(EN, OUTPUT);
Serial.begin(19200);
}

void loop()
{
// receive data
digitalWrite(EN, LOW);//Enable Receiving Data
val = Serial.read();
if (-1 != val) {
if ('A' == val) {
digitalWrite(ledPin, HIGH);
delay(500);
digitalWrite(ledPin, LOW);
delay(500);
}
}
}