Serial.available( )

The Serial.available( ) function in Arduino gets the stored bytes from the serial port that are available for reading. It is the data, which is already stored and arrived in the serial buffer. The serial buffer in Arduino holds the 64 bytes.

Serial.available( ) function inherits from the utility class called stream. The stream is only invoked when the function relying on it is called. The stream class is considered as the base class for binary and character-based streams.

Let's understand with an example.

Consider the below code.

int arrivingdatabyte = 0; // initializing the incoming serial byte
void setup( )
{
Serial.begin(9600); // 9600 is the data rate in bps (bits per second).
}
void loop( ) // loop function that executes repeatedly
{
if(Serial.available( ) > 0) //  It will only send data when the received data is greater than 0.
{
arrivingdatabyte = Serial.read( );  // It will read the incoming or arriving data byte
Serial.print("data byte received:");
Serial.println(arrivingdatabyte, DEC); // here, DEC means Decimal
}
}

In case of the Arduino Mega, the ports available are:

Serial1.available( )

Serial2.available( )

Serial3.available( )

Let's understand the concept of Mega with an example.

In this example, the data will be read and sent from one port to another.

It will read data from port 0 and will then send the data to port 1.

Consider the below code.

void setup( )
{
Serial.begin(4800);
Serial1.begin(4800);
}
// two if conditions will be used.
//In first, if the data is available in the port 0, it will send to the port 1. In second, if the data is available in the port 1, it will send to the port 0.
void loop( )
{
// Now,the data will be read from port 0 and will be sent to the port 1.
if( Serial.available( ) )
{
int incomingdatabyte = Serial.read( );
Serial1.print('incomingdatabyte, byte');
}
// Now,the data will be read from port 1 and will be sent to the port 0.
if( Serial1.available( ) )
{
int incomingdatabyte = Serial1.read( );
Serial.print('incomingdatabyte, byte');
}
}

We can also check the errors in our code by compiling. For that, click on the Verify button.

The Arduino screen will look like the below image: