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Serial

Serial is used for communication between the board and a computer or other devices. CT-ARM has one main 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().

CT-ARM has 4 additional serial ports: Serial2 on pins 8 (RX) and 9 (TX), Serial3 on pins A4 (RX) and A5 (TX), Serial4 on pins SCL (RX) and SDA (TX) , and Serial5 on pins 10 (RX) and 11 (TX). To use these pins to communicate with your personal computer, you will need an additional USB-to-serial adaptor, as they are not connected to the CT-ARM's USB-to-serial adaptor. To use them to communicate with an external TTL serial device, connect the TX pin to your device's RX pin, the RX to your device's TX pin, and the ground of your CT-ARM to your device's ground.

CT-ARM also has 1 special port: Serial1, which shares same RX and TX pins as Serial. To use Serial1, just simply cut the track between pad UART0 and center pad at the back of CT-ARM board, then solder pad UART1 and center pad together. The advantage is that pin 0 and 1 are no longer interferring with Serial debugging, and the users can use these 2 pins for another extra TTL serial device.

The UART pinouts are listed as below:

UART	RX	TX
Serial	0 (default)	1 (default)
Serial1	0	1
Serial2	8	9
Serial3	A4	A5
Serial4	SCL	SDA
Serial5	10	11

Warning

Serial communication on pins TX/RX on CT-ARM uses TTL logic levels 5V. Don't connect these pins directly to an RS232 serial port; they operate at ± 12V and can damage your CT-ARM board.

If (Serial)

Description

Indicates if the specified Serial port is ready.

Syntax

If(Serial)

If(Serial1)

If(Serial2)

If(Serial3)

If(Serial4)

If(Serial5)

Parameters

None

Return

boolean : returns true if the specified serial port is available.

Example

void setup() { 
 //Initialize serial and wait for port to open:
  Serial.begin(9600); 
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB
  }
} 

void loop() { 
 //proceed normally
} 

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()

Serial1.available()

Serial2.available()

Serial3.available()

Serial4.available()

Serial5.available()

Parameters

None

Return

the number of bytes available to read

Example

Serial Example:

int incomingByte = 0;   // for incoming serial data

void setup() {
  // opens serial port, sets data rate to 9600 bps
  Serial.begin(9600);
}

void loop() {

  // send data only when you receive data:
  if (Serial.available() > 0) {
     // read the incoming byte:
     incomingByte = Serial.read();

     // say what you got:
     Serial.print("I received: ");
     Serial.println(incomingByte, DEC);
  }
}

Serial2 Example:

void setup() {
  // opens port 0 and port 2, both sets data rate to 9600 bps
  Serial.begin(9600);
  Serial2.begin(9600);
}

void loop() {
  // read from port 0, send to port 2:
  if (Serial.available()) {
    int inByte = Serial.read();
    Serial2.print(inByte, BYTE); 

  }
  // read from port 2, send to port 0:
  if (Serial2.available()) {
    int inByte = Serial2.read();
    Serial.print(inByte, BYTE); 
  }
}

begin()

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.

Syntax

Serial.begin()

Serial1.begin()

Serial2.begin()

Serial3.begin()

Serial4.begin()

Serial5.begin()

Parameters

• speed: in bits per second (baud) - long

Return

None

Example

void setup() {
    Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
    Serial2.begin(19200); // opens serial port 2 , sets data rate to 19200 bps
    Serial5.begin(4800); // opens serial port 5, sets data rate to 4800 bps
}

void loop() {}

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

Serial1.end

Serial2.end

Serial3.end

Serial4.end

Serial5.end

Parameters

None

Return

None

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)

Return

boolean

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)

Return

boolean

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()

Parameters

None

Return

None

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 Stream utility class.

Syntax

Serial.peek()

Parameters

None

Return

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

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)

Return

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

Example

/*
Uses a FOR loop for data and prints a number in various formats.
*/
int x = 0;    // variable

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
}

println()

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)

Return

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

Example

/*
  Analog input

 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);
}

read()

Description

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

Syntax

Serial.read()

Serial1.read()

Serial2.read()

Serial3.read()

Serial4.read()

Serial5.read()

Parameters

None

Return

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

Example

int incomingByte = 0;   // for incoming serial data

void setup() {
  Serial.begin(9600);     // opens serial port, sets data rate to 9600 bps
}

void loop() {
  // send data only when you receive data:
  if (Serial.available() > 0) {
    // read the incoming byte:
    incomingByte = Serial.read();

    // say what you got:
    Serial.print("I received: ");
    Serial.println(incomingByte, DEC);
  }
}

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)

Return

byte

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)

Return

byte

readString()

Description

Reads characters from the serial buffer into a string. The function terminates if it times out (see setTimeout()).

Syntax

Serial.readString()

Parameters

None

Return

A string read from the serial buffer

readStringUntil()

Description

Reads characters from the serial buffer into a string. The function terminates if the terminator character is detected or it times out (see setTimeout()).

Syntax

Serial.readStringUntil(terminator)

Parameters

• terminator : the character to search for (char)

Return

The entire string read from the serial buffer, until the terminator character is detected

setTimeout()

Description

Sets the maximum milliseconds to wait for serial data when using Serial.readBytesUntil() and Serial.readBytes(). It defaults to 1000 milliseconds.

Syntax

Serial.setTimeout(time)

Parameters

• time : timeout duration in milliseconds (long).

Return

None

write()

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)

Also supports: Serial1, Serial2, Serial3, Serial4 and Serial5 (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

Return

byte

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

Example

void setup(){
  Serial.begin(9600);
}

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.
}

serialEvent()

Description

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

Syntax

void serialEvent(){
//statements
}

void serialEvent1(){
//statements
}

void serialEvent2(){
//statements
}

void serialEvent3(){
//statements
}

void serialEvent4(){
//statements
}

void serialEvent5(){
//statements
}

Parameters

statements: any valid statements