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Serial

Used for communication between the Arduino board and a computer or other devices. All Arduino boards have at least one serial port (also known as a UART or USART): Serial. It communicates on digital pins 0 (RX) and 1 (TX) as well as with the computer via USB. Thus, if you use these functions, you cannot also use pins 0 and 1 for digital input or output.

You can use the Arduino environment’s built-in serial monitor to communicate with an Arduino board. Click the serial monitor button in the toolbar and select the same baud rate used in the call to begin().[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column width=”1/1″][vc_tour][vc_tab title=”if (Serial)” tab_id=”1395136729-1-37″][vc_column_text]

Description

Indicates if the specified Serial port is ready.

On the Leonardo, if (Serial) indicates wether or not the USB CDC serial connection is open. For all other instances, including if (Serial1) on the Leonardo, this will always returns true.

This was introduced in Arduino 1.0.1.

Syntax

All boards:
if (Serial)

Arduino Leonardo specific:
if (Serial1)
Arduino Mega specific:
if (Serial1)
if (Serial2)
if (Serial3)

Parameters

none

Returns

boolean : returns true if the specified serial port is available. This will only return false if querying the Leonardo’s USB CDC serial connection before it is ready.

Example:

[/vc_column_text][/vc_tab][vc_tab title=”available()” tab_id=”1395136729-2-33″][vc_column_text]

available()

Description

Get the number of bytes (characters) available for reading from the serial port. This is data that’s already arrived and stored in the serial receive buffer (which holds 64 bytes). available() inherits from the Stream utility class.

Syntax

Serial.available()

Arduino Mega only:
Serial1.available()
Serial2.available()
Serial3.available()

Parameters

none

Returns

the number of bytes available to read

Example

Arduino Mega example:

}

void loop() {
// read from port 0, send to port 1:
if (Serial.available()) {
int inByte = Serial.read();
Serial1.print(inByte, BYTE);

}
// read from port 1, send to port 0:
if (Serial1.available()) {
int inByte = Serial1.read();
Serial.print(inByte, BYTE);
}
}

[/vc_column_text][/vc_tab][vc_tab title=”begin()” tab_id=”1395138088312-2-5″][vc_column_text]

Description

Sets the data rate in bits per second (baud) for serial data transmission. For communicating with the computer, use one of these rates: 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, or 115200. You can, however, specify other rates – for example, to communicate over pins 0 and 1 with a component that requires a particular baud rate.

An optional second argument configures the data, parity, and stop bits. The default is 8 data bits, no parity, one stop bit.

Syntax

Serial.begin(speed)
Serial.begin(speed, config)

Arduino Mega only:
Serial1.begin(speed)
Serial2.begin(speed)
Serial3.begin(speed)
Serial1.begin(speed, config)
Serial2.begin(speed, config)
Serial3.begin(speed, config)

Parameters

speed: in bits per second (baud) – long
config: sets data, parity, and stop bits. Valid values are :

• SERIAL_5N1
• SERIAL_6N1
• SERIAL_7N1
• SERIAL_8N1 (the default)
• SERIAL_5N2
• SERIAL_6N2
• SERIAL_7N2
• SERIAL_8N2
• SERIAL_5E1
• SERIAL_6E1
• SERIAL_7E1
• SERIAL_8E1
• SERIAL_5E2
• SERIAL_6E2
• SERIAL_7E2
• SERIAL_8E2
• SERIAL_5O1
• SERIAL_6O1
• SERIAL_7O1
• SERIAL_8O1
• SERIAL_5O2
• SERIAL_6O2
• SERIAL_7O2
• SERIAL_8O2

Returns

nothing

Example:

void loop() {}

Arduino Mega example:

void setup(){
Serial.begin(9600);
Serial1.begin(38400);
Serial2.begin(19200);
Serial3.begin(4800);

Serial.println(“Hello Computer”);
Serial1.println(“Hello Serial 1”);
Serial2.println(“Hello Serial 2”);
Serial3.println(“Hello Serial 3″);
}

void loop() {}

[/vc_column_text][/vc_tab][vc_tab title=”end()” tab_id=”1395138298232-3-9″][vc_column_text]

end()

Description

Disables serial communication, allowing the RX and TX pins to be used for general input and output. To re-enable serial communication, call Serial.begin().

Syntax

Serial.end()

Arduino Mega only:
Serial1.end()
Serial2.end()
Serial3.end()

Parameters

none

Returns

nothing[/vc_column_text][/vc_tab][vc_tab title=”Serial.find()” tab_id=”1395138388285-4-3″][vc_column_text]

Serial.find()

Description

Serial.find() reads data from the serial buffer until the target string of given length is found. The function returns true if target string is found, false if it times out.

Serial.find() inherits from the Stream utility class.

Syntax

Serial.find(target)

Parameters

target : the string to search for (char)

Returns

boolean[/vc_column_text][/vc_tab][vc_tab title=”Serial.findUntil()” tab_id=”1395138482320-5-0″][vc_column_text]

Serial.findUntil()

Description

Serial.findUntil() reads data from the serial buffer until a target string of given length or terminator string is found.

The function returns true if the target string is found, false if it times out.

Serial.findUntil() inherits from the Stream utility class.

Syntax

Serial.findUntil(target, terminal)

Parameters

target : the string to search for (char)
terminal : the terminal string in the search (char)

Returns

boolean[/vc_column_text][/vc_tab][vc_tab title=”flush()” tab_id=”1395138572674-6-9″][vc_column_text]

flush()

Description

Waits for the transmission of outgoing serial data to complete. (Prior to Arduino 1.0, this instead removed any buffered incoming serial data.)

flush() inherits from the Stream utility class.

Syntax

Serial.flush()

Arduino Mega only:
Serial1.flush()
Serial2.flush()
Serial3.flush()

Parameters

none

Returns

nothing[/vc_column_text][/vc_tab][vc_tab title=”Serial.parseFloat()” tab_id=”1395138701607-7-9″][vc_column_text]

Serial.parseFloat()

Description

Serial.parseFloat() returns the first valid floating point number from the Serial buffer. Characters that are not digits (or the minus sign) are skipped. parseFloat() is terminated by the first character that is not a floating point number.

Serial.parseFloat() inherits from the Stream utility class.

Syntax

Serial.parseFloat()

Parameters

none

Returns

float[/vc_column_text][/vc_tab][vc_tab title=”parseInt()” tab_id=”1395138794944-8-10″][vc_column_text]

parseInt()

Description

Looks for the next valid integer in the incoming serial stream. parseInt() inherits from the Stream utility class.

If no valid integer is found within one second (adjustable through Serial.setTimeout() ) a default value of 0 will be returned.

Syntax

Serial.parseInt()

Arduino Mega only:
Serial1.parseInt()
Serial2.parseInt()
Serial3.parseInt()

Parameters

none

Returns

int : the next valid integer[/vc_column_text][/vc_tab][vc_tab title=”peek()” tab_id=”1395138907273-9-0″][vc_column_text]

peek()

Description

Returns the next byte (character) of incoming serial data without removing it from the internal serial buffer. That is, successive calls to peek() will return the same character, as will the next call to read(). peek() inherits from the Streamutility class.

Syntax

Serial.peek()

Arduino Mega only:
Serial1.peek()
Serial2.peek()
Serial3.peek()

Parameters

None

Returns

the first byte of incoming serial data available (or -1 if no data is available) – int[/vc_column_text][/vc_tab][vc_tab title=”print()” tab_id=”1395138976860-10-7″][vc_column_text]

print()

Description

Prints data to the serial port as human-readable ASCII text. This command can take many forms. Numbers are printed using an ASCII character for each digit. Floats are similarly printed as ASCII digits, defaulting to two decimal places. Bytes are sent as a single character. Characters and strings are sent as is. For example:

• Serial.print(78) gives “78”
• Serial.print(1.23456) gives “1.23”
• Serial.print(‘N’) gives “N”
• Serial.print(“Hello world.”) gives “Hello world.”

An optional second parameter specifies the base (format) to use; permitted values are BIN (binary, or base 2), OCT (octal, or base 8), DEC (decimal, or base 10), HEX (hexadecimal, or base 16). For floating point numbers, this parameter specifies the number of decimal places to use. For example:

• Serial.print(78, BIN) gives “1001110”
• Serial.print(78, OCT) gives “116”
• Serial.print(78, DEC) gives “78”
• Serial.print(78, HEX) gives “4E”
• Serial.println(1.23456, 0) gives “1”
• Serial.println(1.23456, 2) gives “1.23”
• Serial.println(1.23456, 4) gives “1.2346”

You can pass flash-memory based strings to Serial.print() by wrapping them with F(). For example :

• Serial.print(F(“Hello World”))

To send a single byte, use Serial.write().

Syntax

Serial.print(val)
Serial.print(val, format)

Parameters

val: the value to print – any data type

format: specifies the number base (for integral data types) or number of decimal places (for floating point types)

Returns

size_t (long): print() returns the number of bytes written, though reading that number is optional

Example:

void setup() {
Serial.begin(9600);      // open the serial port at 9600 bps:
}

void loop() {
// print labels
Serial.print(“NO FORMAT”);       // prints a label
Serial.print(“\t”);              // prints a tab

Serial.print(“DEC”);
Serial.print(“\t”);

Serial.print(“HEX”);
Serial.print(“\t”);

Serial.print(“OCT”);
Serial.print(“\t”);

Serial.print(“BIN”);
Serial.print(“\t”);

for(x=0; x< 64; x++){    // only part of the ASCII chart, change to suit

// print it out in many formats:
Serial.print(x);       // print as an ASCII-encoded decimal – same as “DEC”
Serial.print(“\t”);    // prints a tab

Serial.print(x, DEC);  // print as an ASCII-encoded decimal
Serial.print(“\t”);    // prints a tab

Serial.print(x, HEX);  // print as an ASCII-encoded hexadecimal
Serial.print(“\t”);    // prints a tab

Serial.print(x, OCT);  // print as an ASCII-encoded octal
Serial.print(“\t”);    // prints a tab

Serial.println(x, BIN);  // print as an ASCII-encoded binary
//                             then adds the carriage return with “println”
delay(200);            // delay 200 milliseconds
}
Serial.println(“”);      // prints another carriage return
}

Programming Tips

As of version 1.0, serial transmission is asynchronous; Serial.print() will return before any characters are transmitted.[/vc_column_text][/vc_tab][vc_tab title=”println()” tab_id=”1395139082179-11-10″][vc_column_text]

Description

Prints data to the serial port as human-readable ASCII text followed by a carriage return character (ASCII 13, or ‘\r’) and a newline character (ASCII 10, or ‘\n’). This command takes the same forms as Serial.print().

Syntax

Serial.println(val)
Serial.println(val, format)

Parameters

val: the value to print – any data type

format: specifies the number base (for integral data types) or number of decimal places (for floating point types)

Returns

size_t (long): println() returns the number of bytes written, though reading that number is optional

Example:

reads an analog input on analog in 0, prints the value out.

created 24 March 2006
by Tom Igoe
*/

int analogValue = 0;    // variable to hold the analog value

void setup() {
// open the serial port at 9600 bps:
Serial.begin(9600);
}

void loop() {
// read the analog input on pin 0:
analogValue = analogRead(0);

// print it out in many formats:
Serial.println(analogValue);       // print as an ASCII-encoded decimal
Serial.println(analogValue, DEC);  // print as an ASCII-encoded decimal
Serial.println(analogValue, HEX);  // print as an ASCII-encoded hexadecimal
Serial.println(analogValue, OCT);  // print as an ASCII-encoded octal
Serial.println(analogValue, BIN);  // print as an ASCII-encoded binary

// delay 10 milliseconds before the next reading:
delay(10);
}

[/vc_column_text][/vc_tab][vc_tab title=”read()” tab_id=”1395139219269-12-7″][vc_column_text]

Description

Reads incoming serial data. read() inherits from the Stream utility class.

Syntax

Serial.read()

Arduino Mega only:
Serial1.read()
Serial2.read()
Serial3.read()

Parameters

None

Returns

the first byte of incoming serial data available (or -1 if no data is available) – int

Example

[/vc_column_text][/vc_tab][vc_tab title=”Serial.readBytes()” tab_id=”1395139278655-13-0″][vc_column_text]

Serial.readBytes()

Description

Serial.readBytes() reads characters from the serial port into a buffer. The function terminates if the determined length has been read, or it times out (see Serial.setTimeout()).

Serial.readBytes() returns the number of characters placed in the buffer. A 0 means no valid data was found.

Serial.readBytes() inherits from the Stream utility class.

Syntax

Serial.readBytes(buffer, length)

Parameters

buffer: the buffer to store the bytes in (char[] or byte[])
length : the number of bytes to read (int)

Returns

byte[/vc_column_text][/vc_tab][vc_tab title=”Serial.readBytesUntil()” tab_id=”1395139313892-14-10″][vc_column_text]

Serial.readBytesUntil()

Description

Serial.readBytesUntil() reads characters from the serial buffer into an array. The function terminates if the terminator character is detected, the determined length has been read, or it times out (see Serial.setTimeout()).

Serial.readBytesUntil() returns the number of characters read into the buffer. A 0 means no valid data was found.

Serial.readBytesUntil() inherits from the Stream utility class.

Syntax

Serial.readBytesUntil(character, buffer, length)

Parameters

character : the character to search for (char)
buffer: the buffer to store the bytes in (char[] or byte[]) length : the number of bytes to read (int)

Returns

byte[/vc_column_text][/vc_tab][vc_tab title=”Serial.setTimeout()” tab_id=”1395139426956-15-10″][vc_column_text]

Serial.setTimeout()

Description

Serial.setTimeout() sets the maximum milliseconds to wait for serial data when using Serial.readBytesUntil() orSerial.readBytes(). It defaults to 1000 milliseconds.

Serial.setTimeout() inherits from the Stream utility class.

Syntax

Serial.setTimeout(time)

Parameters

time : timeout duration in milliseconds (long).

Parameters

None[/vc_column_text][/vc_tab][vc_tab title=”write()” tab_id=”1395139478191-16-1″][vc_column_text]

Description

Writes binary data to the serial port. This data is sent as a byte or series of bytes; to send the characters representing the digits of a number use the print() function instead.

Syntax

Serial.write(val)
Serial.write(str)
Serial.write(buf, len)

Arduino Mega also supports: Serial1, Serial2, Serial3 (in place of Serial)

Parameters

val: a value to send as a single byte

str: a string to send as a series of bytes

buf: an array to send as a series of bytes

len: the length of the buffer

Returns

byte
write() will return the number of bytes written, though reading that number is optional

Example

void loop(){
Serial.write(45); // send a byte with the value 45

int bytesSent = Serial.write(“hello”); //send the string “hello” and return the length of the string.
}

[/vc_column_text][/vc_tab][vc_tab title=”serialEvent()” tab_id=”1395139546826-17-4″][vc_column_text]

serialEvent()

Description

Called when data is available. Use Serial.read() to capture this data.

NB : Currently, serialEvent() is not compatible with the Esplora, Leonardo, or Micro

Syntax

Arduino Mega only:

void serialEvent2(){
//statements
}

void serialEvent3(){
//statements
}

Parameters

statements: any valid statements[/vc_column_text][/vc_tab][/vc_tour][/vc_column][/vc_row]