Arduino MEGA2560與藍牙的通信（玄學）問題

使用Arduino UNO和HC05進行通信的時候，會用到一個語句

SoftwareSerial BT(10, 11);

這是定義一個SoftwareSerial對象：BT，並初始化了RX和TX的引腳，這之後才能通過BT對象對藍牙進行操作。

但當與HC05通信時的單片機變成MEGA的時候，事情就變得玄學了起來。

某位小夥伴徹夜的實驗表明，這條語句似乎對MEGA並不會起什麼作用…

經過一番查找，我在Arduino的庫文件裏找到了這幾條語句：

// These serial port names are intended to allow libraries and architecture-neutral
// sketches to automatically default to the correct port name for a particular type
// of use.  For example, a GPS module would normally connect to SERIAL_PORT_HARDWARE_OPEN,
// the first hardware serial port whose RX/TX pins are not dedicated to another use.
//
// SERIAL_PORT_MONITOR        Port which normally prints to the Arduino Serial Monitor
//
// SERIAL_PORT_USBVIRTUAL     Port which is USB virtual serial
//
// SERIAL_PORT_LINUXBRIDGE    Port which connects to a Linux system via Bridge library
//
// SERIAL_PORT_HARDWARE       Hardware serial port, physical RX & TX pins.
//
// SERIAL_PORT_HARDWARE_OPEN  Hardware serial ports which are open for use.  Their RX & TX
//                            pins are NOT connected to anything by default.
#define SERIAL_PORT_MONITOR         Serial
#define SERIAL_PORT_HARDWARE        Serial
#define SERIAL_PORT_HARDWARE1       Serial1
#define SERIAL_PORT_HARDWARE2       Serial2
#define SERIAL_PORT_HARDWARE3       Serial3
#define SERIAL_PORT_HARDWARE_OPEN   Serial1
#define SERIAL_PORT_HARDWARE_OPEN1  Serial2
#define SERIAL_PORT_HARDWARE_OPEN2  Serial3

也就是說，MEGA自己定義了Serial，Serial1，Serial2，Serial3這些對象，如果直接把藍牙的rxtx接在MEGA的第一組txrx上，然後直接調用Serial1對象，就可以實現通信，譬如這樣：

#include <SoftwareSerial.h> 

// Pin10爲RX，接HC05的TXD
// Pin11爲TX，接HC05的RXD
//SoftwareSerial BT(14, 15); 這是沒有用的
char val;

void setup() {
  Serial.begin(9600); 
  Serial.println("BT is ready!");
  Serial3.begin(9600);
}

void loop() {
  if (Serial.available()) {
    val = Serial.read();
    Serial3.print(val);
    delay(20);
  }

  if (Serial3.available()) {
    val = Serial3.read();
    Serial.print(val);
    delay(20);
  }
  delay(20);
}

綜上所述，使用MEGA通過藍牙通信的時候，就不要自己去定義串口對象了，直接使用MEGA提供的Serial1，Serial2，Serial3就可以