Serial Communications (SoftwareSerial Class)

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SoftwareSerial
Utility

SoftwareSerial is a library that enables serial communication with a digital pin other than the serial port. It is possible to have multiple software serial ports with speeds up to 115200bps. However, be careful when the baud rate is 115200bps because the reception latch timing is not so accurate. The receive buffer is fixed at 256 bytes.

To use it, specify #include <SoftwareSerial.h>. You will need to create an instance of SoftwareSerial class.

Constructor for SoftwareSerial

Description

This is a constructor for creating an instance of the SoftwareSerial class.

Syntax

SoftwareSerial(receivePin, transmitPin)
SoftwareSerial(receivePin, transmitPin, inverse_logic)

Parameters

receivePin: Receive pin
transmitPin: Transmit pin
inverse_logic: Inverse logic (default false)

Returns

None

begin

Description

Sets the data rate in bits per second (baud).

Syntax

serial.begin(int speed)

Parameters

speed: In bits per second (baud)

Returns

None

end

Description

Disables serial communication port.

Syntax

serial.end()

Parameters

None

Returns

None

available

Description

Gets the number of bytes (characters) available for reading from the serial port.

Syntax

int serial.available()

Parameters

None

Returns

The number of bytes available in the serial buffer. Returns 0 when there is no data.

read

Description

Reads 1 byte of data from the receive buffer in the the serial communications port.

Syntax

int serial.read()

Parameters

None

Returns

Data. If no data available, returns -1.

peek

Description

Returns the next byte (character) of incoming serial data in the serial communications port without removing it from the receive buffer. CRLF conversion is not carried out.

Syntax

int serial.peek()

Parameters

None

Returns

The first byte of incoming serial data available (or -1 if no data is available).

flush

Description

Waits until the send buffer of the serial communications port is empty.

Syntax

serial.flush()

Parameters

None

Returns

None

write

Description

Writes a character string or data to the serial communications port.

Syntax

serial.write(const char* str)
serial.write(const unsigned char* buf, int len)

Parameters

str: A string to send as a series of bytes
buf: An array (pointer) to send data
len: Length of the output (written) data

Returns

The number of bytes of output (written) data.

print

Description

Prints a character string to the serial communications port.

Syntax

serial.print(val)
serial.print(val, format)

Parameters

val: The value or character string to print
format: Specifies the number base for values (BIN: binary or base 2, OCT: octal or base 8, DEC: decimal or base 10, HEX: hexadecimal or base 16)

Returns

The number of bytes printed.

println

Description

Prints a character string to the serial communications port followed by a carriage return.

Syntax

serial.println(val)
serial.println(val, format)

Parameters

val: The value or character string to print
format: Specifies the number base for values (BIN: binary or base 2, OCT: octal or base 8, DEC: decimal or base 10, HEX: hexadecimal or base 16)

Returns

The number of bytes printed.

listen

Description

Enables the selected software serial port to listen. Only one software serial port can listen at a time; data that arrives for other ports will be discarded. Any data already received is discarded during the call to listen() (unless the given instance is already listening).

Syntax

bool serial.listen()

Parameters

None

Returns

True or False

isListening

Description

Tests to see if requested software serial port is actively listening.

Syntax

bool serial.isListening()

Parameters

None

Returns

True or False

overflow

Description

Tests to see if a software serial buffer overflow has occurred. Calling this function clears the overflow flag, meaning that subsequent calls will return false unless another byte of data has been received and discarded in the meantime.

Syntax

bool serial.overflow()

Parameters

None

Returns

True or False

This is an example that specifies Pin 10 as receive and Pin 11 as transmit and outputs the value of A0.

        #include <Arduino.h>
        #include <SoftwareSerial.h>
            
        SoftwareSerial serial(10, 11); // RX: 10, TX:11
        int analogValue;
            
        void setup()
        {
            serial.begin(9600);
        }
            
        void loop()
        {
            analogValue = analogRead(A0);
            delay(100);
        }