QwiicUART Library

This is an Arduino library to utilize the NXP SC16IS741 as a hardware serial port controlled via I²C.

QwiicUART Board

Examples

Methods

QwiicUART()

Description

Creates a QwiicUART object and sets the I²C port and address to use.

Syntax

• QwiicUART
• QwiicUART(wire)
• QwiicUART(wire, address)

Parameters

• wire: the TwoWire object to use to talk to the UART chip. The default value is Wire.
• address: The I²C address of the UART chip. Typical values are:
  0x48 (default)
  0x49
0x4A
0x4B

Example

# include <QwiicUART.h>

QwiicUART qSerial(Wire, 0x48);

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

qSerial.available()

Parameters

qSerial: a QwiicUART serial port object.

Returns

The number of bytes available to read.

Example

# include <QwiicUART.h>

QwiicUART qSerial;

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

void loop() {
  // read from Serial, send to qSerial:
  if (Serial.available()) {
    int inByte = Serial.read();
    qSerial.print(inByte, DEC);
  }
  // read from qSerial, send to Serial:
  if (qSerial.available()) {
    int inByte = qSerial.read();
    Serial.print(inByte, DEC);
  }
}

availableForWrite()

Description

Get the number of bytes (characters) available for writing in the serial buffer without blocking the write operation.

Syntax

qSerial.availableForWrite()

Parameters

qSerial: a QwiicUART serial port object.

Returns

The number of bytes available to write.

begin()

Description

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

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

Syntax

• qSerial.begin(baud)
• qSerial.begin(baud, config)

Parameters

• qSerial: a QwiicUART serial port object.
• baud: in bits per second. Common values are: 1200, 2400, 4800, 9600, 16200, 38400, 57600, and 115200. Allowed data types: long.
• config: sets data, parity, and stop bits. Valid values are:
  • SERIAL_5N1
  • SERIAL_6N1
  • SERIAL_7N1
  • SERIAL_8N1 (default)
  • SERIAL_5N2
  • SERIAL_6N2
  • SERIAL_7N2
  • SERIAL_8N2
  • SERIAL_5E1: even parity
  • SERIAL_6E1
  • SERIAL_7E1
  • SERIAL_8E1
  • SERIAL_5E2
  • SERIAL_6E2
  • SERIAL_7E2
  • SERIAL_8E2
  • SERIAL_5O1: odd parity
  • SERIAL_6O1
  • SERIAL_7O1
  • SERIAL_8O1
  • SERIAL_5O2
  • SERIAL_6O2
  • SERIAL_7O2
  • SERIAL_8O2

Example

# include <QwiicUART.h>

QwiicUART qSerial;

void setup() {
  Wire.begin();
  qSerial.begin(9600);
}

void loop() {}

[!NOTE] The actual baud rate of the SC16IS741 is set using an integer $divisor$. When using a 1.8432 MHz clock, as the QwiicUART board does, the baud rate will be: $$\frac{115200}{divisor}$$ This library selects the $divisor$ value that will result in the baud rate closest to what is asked for, but because it is an integer, there is limited resolution, particularly at the higher baud rates.

$divisor$	Baud Rate
1	115200
2	57600
3	38400
4	28800
5	23040
6	19200

end()

Description

Runs flush() then resets the SC16IS741.

Syntax

qSerial.end()

Parameters

qSerial: a QwiicUART serial port object.

find()

Description

Reads data from the serial buffer until the target is found. The function returns true if target is found, false if it times out.

find() inherits from the Stream utility class.

Syntax

• qSerial.find(target)
• qSerial.find(target, length)

Parameters

• qSerial: a QwiicUART serial port object.
• target: the string to search for. Allowed data types: char.
• length: length of the target. Allowed data types: size_t.

Returns

Data type: bool.

findUntil()

Description

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.

findUntil() inherits from the Stream utility class.

Syntax

qSerial.findUntil(target, terminal)

Parameters

• qSerial: a QwiicUART serial port object.
• target: the string to search for. Allowed data types: char.
• terminal: the terminal string in the search. Allowed data types: char.

Returns

Data type: bool.

flush()

Description

Waits for the transmission of outgoing serial data to complete.

flush() inherits from the Stream utility class.

Syntax

qSerial.flush()

Parameters

qSerial: a QwiicUART serial port object.

parseFloat()

Description

Returns the first valid floating point number from the Serial buffer. parseFloat() is terminated by the first character that is not a floating point number. The function terminates if it times out (see setTimeout()).

parseFloat() inherits from the Stream utility class.

Syntax

• qSerial.parseFloat()
• qSerial.parseFloat(lookahead)
• qSerial.parseFloat(lookahead, ignore)

Parameters

• qSerial: a QwiicUART serial port object.
• lookahead: the mode used to look ahead in the stream for a floating point number. Allowed data types: LookaheadMode. Allowed values:
  • SKIP_ALL: all characters other than a minus sign, decimal point, or digits are ignored when scanning the stream for a floating point number. This is the default mode.
  • SKIP_NONE: Nothing is skipped, and the stream is not touched unless the first waiting character is valid.
  • SKIP_WHITESPACE: Only tabs, spaces, line feeds, and carriage returns are skipped.
• ignore: used to skip the indicated char in the search. Used for example to skip thousands divider. Allowed data types: char

Returns

Data type: float.