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5.12 Serial Read¶

You may have noticed this when using the Serial.print() function. Since there is printing, is there reading? What is the text box on the Serial Monitor used for? Yes, you guessed it, there are ways to control programs and circuits by entering information through the text box on the Serial Monitor.

In this project, we will use the I2C LCD1602 to display the text entered in the Serial Monitor in order to experience the usage of Serial.read().

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name

ITEMS IN THIS KIT

LINK

3 in 1 Starter Kit

380+

3 in 1 Starter Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION

PURCHASE LINK

SunFounder R3 Board

BUY

Jumper Wires

BUY

I2C LCD1602

BUY

Schematic

../_images/circuit_7.1_lcd1602.png

Wiring

../_images/lcd_bb.jpg

Code

Note

  • Open the 5.12.serial_read.ino file under the path of 3in1-kit\basic_project\5.12.serial_read.

  • Or copy this code into Arduino IDE.

  • The LiquidCrystal I2C library is used here, you can install it from the Library Manager.

    ../_images/lib_liquidcrystal_i2c.png

After the code is uploaded successfully, you can enter text in the text box on the serial monitor, and the LCD will display the information.

How it works?

void loop()
{
// when characters arrive over the serial port...
    if (Serial.available()) {
        // wait a bit for the entire message to arrive
        delay(100);
        // clear the screen
        lcd.clear();
        // read all the available characters
        while (Serial.available() > 0) {
            // display each character to the LCD
            lcd.write(Serial.read());
        }
    }
}

  • Serial.available() can get the number of characters available in the incoming stream when you type something from the textbox. Since there are two terminators in the input, you actually have 3 characters when you type A, and 4 characters when you type AB.

  • Serial.read() will take the first character from the incoming stream. For example, if you typed AB , calling Serial.read() only once, will get the character A; The second call, you will get B; the third and fourth call, you will get two end symbols; calling this function when the input stream has no characters available will result in an error.

To sum up, it is common to combine the above two, using a while loop to read all characters entered each time.

while (Serial.available() > 0) {
    Serial.print(Serial.read());
}

By the way, if you don’t use Serial.read() to get characters from the incoming stream, the characters from the incoming stream will be stacked together. For example, if you type A followed by AB, the incoming stream will accumulate 7 characters.