简单的读写

此示例侦听通过串行连接进入的输入，然后将其重新发送回同一连接。

byte incomingBytes;

void setup() {                
  Serial.begin(9600); // Opens serial port, sets data rate to 9600 bps.
}

void loop() {
  // Send data only when you receive data.
  if (Serial.available() > 0) {
    // Read the incoming bytes.
    incomingBytes = Serial.read();

    // Echo the data.
    Serial.println(incomingBytes);
  }
}