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SoftwareSerial : 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
Parameters
mySerial:the name of the instance to listen
Returns
boolean: Returns true if it replaces another
Example
// software serial : TX = digital pin 10, RX = digital pin 11
SoftwareSerial portOne ( 10 , 11 ) ;
// software serial : TX = digital pin 8, RX = digital pin 9
SoftwareSerial portTwo ( 8 , 9 ) ;
void setup ( )
<
// Start the hardware serial port
Serial . begin ( 9600 ) ;
// Start both software serial ports
portOne. begin ( 9600 ) ;
portTwo. begin ( 9600 ) ;
void loop ( )
<
portOne. listen ( ) ;
if ( portOne. isListening ( ) ) <
Serial . println ( «Port One is listening!» ) ;
> else <
Serial . println ( «Port One is not listening!» ) ;
>
if ( portTwo. isListening ( ) ) <
Serial . println ( «Port Two is listening!» ) ;
> else <
Serial . println ( «Port Two is not listening!» ) ;
>
See also
Corrections, suggestions, and new documentation should be posted to the Forum.
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Software Serial Example
Arduino boards have built in support for serial communication on pins 0 and 1, but what if you need more serial ports? The SoftwareSerial Library has been developed to allow serial communication to take place on the other digital pins of your boards, using software to replicate the functionality of the hardwired RX and TX lines. This can be extremely helpful when the need arises to communicate with two serial enabled devices, or to talk with just one device while leaving the main serial port open for debugging purpose.
In the example below, digital pins 10 and 11 on your Arduino boards are used as virtual RX and TX serial lines. The virtual RX pin is set up to listen for anything coming in on via the main serial line, and to then echo that data out the virtual TX line. Conversely, anything received on the virtual RX is sent out over the hardware TX.
Hardware Required
Circuit
There is no circuit for this example. Make sure that your Arduino board is attached to your computer via USB to enable serial communication through the serial monitor window of the Arduino Software (IDE).
image developed using Fritzing. For more circuit examples, see the Fritzing project page
Schematics
image developed using Fritzing. For more circuit examples, see the Fritzing project page
See also
TwoPortReceive — Two serial ports that receive data switching from one to the other one when a special character is received.
MultiSerialMega — Use two of the serial ports available on the Arduino Mega.
Serial Call Response — Send multiple vairables using a call-and-response (handshaking) method.
Serial Call Response ASCII — Send multiple variables using a call-and-response (handshaking) method, and ASCII-encode the values before sending.
Serial listen arduino
The SoftwareSerial library allows serial communication on other digital pins of an Arduino board, using software to replicate the functionality (hence the name «SoftwareSerial»). It is possible to have multiple software serial ports with speeds up to 115200 bps. A parameter enables inverted signaling for devices which require that protocol.
The version of SoftwareSerial included in 1.0 and later is based on the NewSoftSerial library by ‘Mikal Hart’.
To use this library:
Limitations of This Library
SoftwareSerial library has the following known limitations:
- It cannot transmit and receive data at the same time.
- If using multiple software serial ports, only one can receive data at a time.
- Not all pins on the Mega and Mega 2560 boards support change interrupts, so only the following can be used for RX: 10, 11, 12, 13, 14, 15, 50, 51, 52, 53, A8 (62), A9 (63), A10 (64), A11 (65), A12 (66), A13 (67), A14 (68), A15 (69). Not all pins on the Leonardo and Micro boards support change interrupts, so only the following can be used for RX: 8, 9, 10, 11, 14 (MISO), 15 (SCK), 16 (MOSI).
- On Arduino or Genuino 101 boards the current maximum RX speed is 57600bps.
- On Arduino or Genuino 101 boards RX doesn’t work on digital pin 13.
If your project requires simultaneous data flows, see Paul Stoffregen’s AltSoftSerial library.
- SoftwareSerial example: sometimes one serial port just isn’t enough!
- Two port receive: Work with multiple software serial ports.
Create an instance of a SoftwareSerial object. Multiple SoftwareSerial objects may be created, however only one can be active at a given moment.
- rxPin: the pin on which to receive serial data.
- txPin: the pin on which to transmit serial data.
- inverse_logic: used to invert the sense of incoming bits (the default is normal logic). If set, SoftwareSerial treats a LOW (0v on the pin, normally) on the RX pin as a 1-bit (the idle state) and a HIGH (5V on the pin, normally) as a 0-bit. It also affects the way that it writes to the TX pin. Default value is false.
Get the number of bytes (characters) available for reading from a software serial port. This is data that has already arrived and stored in the serial receive buffer.
The number of bytes available to read.
Sets the speed (baud rate) for the serial communication. Supported baud rates are: 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 31250, 38400, 57600, and 115200 bauds.
- speed: the desired baud rate (long). Supported baud rates are: 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 31250, 38400, 57600, and 115200 bauds.
Tests to see if requested software serial object is actively listening.
Tests to see if a SoftwareSerial 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. The SoftwareSerial buffer can hold up to 64 bytes.
Return a character that was received on the RX pin of the software serial port. Unlike read(), however, subsequent calls to this function will return the same character. Note that only one SoftwareSerial object can receive incoming data at a time (select which one with the listen() function).
The character read or -1 if none is available.
Return a character that was received on the RX pin of the SoftwareSerial objecto. Note that only one SoftwareSerial object can receive incoming data at a time (select which one with the listen() function).
The character read or -1 if none is available.
Prints data to the transmit pin of the SoftwareSerial object. Works the same as the Serial.print() function.
The number of bytes written (reading this number is optional).
Prints data to the transmit pin of the SoftwareSerial object followed by a carriage return and line feed. Works the same as the Serial.println() function.
The number of bytes written (reading this number is optional).
Enables the selected SoftwareSerial object to listen. Only one SoftwareSerial object 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() function (unless the given instance is already listening).
Returns true if it replaces another.
Prints data to the transmit pin of the SoftwareSerial object as raw bytes. Works the same as the Serial.write()function.
The number of bytes written (reading this number is optional).
Adding More Serial Ports to your board.
LAST REVISION: 10/05/2022, 01:00 PM
Arduino boards have built in support for serial communication on pins 0 and 1, but what if you need more serial ports? The SoftwareSerial Library has been developed to allow serial communication to take place on the other digital pins of your boards, using software to replicate the functionality of the hardwired RX and TX lines. This can be extremely helpful when the need arises to communicate with two serial enabled devices, or to talk with just one device while leaving the main serial port open for debugging purpose.
In the example below, digital pins 10 and 11 on your Arduino boards are used as virtual RX and TX serial lines. The virtual RX pin is set up to listen for anything coming in on via the main serial line, and to then echo that data out the virtual TX line. Conversely, anything received on the virtual RX is sent out over the hardware TX.
Hardware Required
Circuit
There is no circuit for this example. Make sure that your Arduino board is attached to your computer via USB to enable serial communication through the serial monitor window of the Arduino Software (IDE).
image developed using Fritzing. For more circuit examples, see the Fritzing project page
Schematics
image developed using Fritzing. For more circuit examples, see the Fritzing project page
Two Port Receive
LAST REVISION: 10/05/2022, 01:00 PM
Arduino boards have built in support for serial communication on pins 0 and 1, but what if you need more serial ports? The SoftwareSerial Library has been developed to allow serial communication to take place on the other digital pins of your boards, using software to replicate the functionality of the hardwired RX and TX lines. This can be extremely helpful when the need arises to communicate with two serial enabled devices, or to talk with just one device while leaving the main serial port open for debugging purpose.
In the example below, digital pins 8 and 10 on your Arduino board are used as virtual RX serial lines. Pins 9 and 11 are virtual TX lines. The board listens on one virtual port (portOne) until it has read all available data. After that, it does the same on the second virtual port (portTwo).
Hardware Required
Circuit
There is no circuit for this example. Make sure that your Arduino board is attached to your computer via USB to enable serial communication through the serial monitor window of the Arduino Software (IDE).
image developed using Fritzing. For more circuit examples, see the Fritzing project page
Schematics
image developed using Fritzing. For more circuit examples, see the Fritzing project page