14.1 Serial

Hardware Wiring

Cited directly from https://www.arduino.cc/en/Tutorial/SoftwareSerialExample:

"There is no circuit for this example. Make sure that your Arduino or Genuino board is attached to your computer via USB to enable serial communication through the serial monitor window of the Arduino Software (IDE).".

Due to the comments inside the sketch code,

"The circuit:

• RX is digital pin 10 (connect to TX of other device)

• TX is digital pin 11 (connect to RX of other device)"

So, to test the serial communication, it's better we found some device/module, which comes with an RX and TX pins. Therefore, we carry out the test with a Wifi ESP8266 module, which will be detailedly discussed again in 14.2 Wifi - ESP8266.

We then connect the pins as:

ESP8266	Arduino UNO R3
GND	GND
VCC	3.3V
CH_PD	3.3V
TX	Virtual RX, namely, pin 10
RX	Virtual TX, namely, pin 11

Serial

Sketch

The code can be found at Examples_Arduino - arduinocc - _001_Serial - _001_Serial.ino, which is directly copied from https://www.arduino.cc/en/Tutorial/SoftwareSerialExample.

/*
  Software serial multple serial test

 Receives from the hardware serial, sends to software serial.
 Receives from software serial, sends to hardware serial.

 The circuit:
 * RX is digital pin 10 (connect to TX of other device)
 * TX is digital pin 11 (connect to RX of other device)

 Note:
 Not all pins on the Mega and Mega 2560 support change interrupts,
 so only the following can be used for RX:
 10, 11, 12, 13, 50, 51, 52, 53, 62, 63, 64, 65, 66, 67, 68, 69

 Not all pins on the Leonardo and Micro support change interrupts,
 so only the following can be used for RX:
 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI).

 created back in the mists of time
 modified 25 May 2012
 by Tom Igoe
 based on Mikal Hart's example

 This example code is in the public domain.

 */
#include <SoftwareSerial.h>

SoftwareSerial mySerial(10, 11); // RX, TX

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(57600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }


  Serial.println("Goodnight moon!");

  // set the data rate for the SoftwareSerial port
  mySerial.begin(4800);
  mySerial.println("Hello, world?");
}

void loop() { // run over and over
  if (mySerial.available()) {
    Serial.write(mySerial.read());
  }
  if (Serial.available()) {
    mySerial.write(Serial.read());
  }
}

Outcome

Serial Port Output from Arduino IDE

However?

So far, we can clearly see Goodnight moon! has been successfully output to the Monitor Serial dialog. However, in our sketch, it's quite clear that Hello, world? should also be output somewhere. But, where? Clearly, mySerial defines the virtual serial port using pin 10 and pin 11. So, there must be a 2nd serial port on the Wifi Module ESP8266.