Arduino Language Reference: Functions and Libraries

2022-10-302022-12-11

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This article introduces the Arduino language reference.

Please refer to the linked articles for detailed explanations and sample programs (sample sketches) for each standard function and standard library.

TOC

Data Types

Data Types	Range	Bits	Explanation
boolean	0, 1	8bit	Used to determine "True" or "False"
char	-128 to 127	8bit	Used for characters
unsigned char	0 to 255	8bit	〃
int	-32,768 to 32,767 (Arduino Due: -2,147,483,648 to 2,147,483,647)	16bit (32bit)	Used for integers
unsigned int	0 to 65,535 (Arduino Due: 0 to 4,294,967,295)	16bit (32bit)	〃
long	-2,147,483,648 to 2,147,483,647	32bit	〃
unsigned long	0 to 4,294,967,295	32bit	〃
float	3.4028235E+38 to -3.4028235E+38	32bit	Used for decimals

Operators

Arithmetic Operators

Arithmetic Operators	Examples	Explanation
+	a = b + c	Assign "b + c" into 'a'
-	a = b - c	Assign "b - c" into 'a'
*	a = b * c	Assign "b * c" into 'a'
/	a = b / c	Assign "b - c" into 'a'
%	a = b % c	Assign "b % c" into 'a' %: remainder
=	a = b	Assign 'b' into 'a'

Compound Operators

Compound Operators	Examples	Explanation
+=	a += b	Assign "b + c" into 'a' (equivalent to the expression "a = b + c")
-=	a -= b	Assign "b - c" into 'a' (equivalent to the expression "a = b - c")
*=	a *= b	Assign "b * c" into 'a' (equivalent to the expression "a = b * c")
/=	a /= b	Assign "b - c" into 'a' (equivalent to the expression "a = b / c")
%=	a %= b	Assign "b % c" into 'a' (equivalent to the expression "a = b % c")

Increment/Decrement Operators

Increment/Decrement Operators	Examples	Explanation
++	a++	returns the old value of 'a' and increment 'a' by one
	++a	increment 'a' by one and returns the new value of 'a'
--	a--	returns the old value of 'a' and decrement 'a' by one
	--a	decrement 'a' by one and returns the new value of 'a'

Comparison Operators

Comparison Operators	Examples	Explanation
==	a == b	True if 'a' and 'b' are equal False if 'a' and 'b' are not equal
!=	a != b	True if 'a' and 'b' are not equal False if 'a' and 'b' are equal
<	a < b	True if 'a' is smaller than 'b' False if 'a' is equal or bigger than 'b'
>	a > b	True if 'a' is bigger than 'b' False if 'a' is equal or smaller than 'b'
<=	a <= b	True if 'a' is smaller than or equal to 'b' False if 'a' is bigger than 'b'
>=	a >= b	True if 'a' is bigger than or equal to 'b' False if 'a' is smaller than 'b'

Boolean Operators

Boolean Operators	Examples	Explanation
&&	(a >= 10) && (a < 100)	True if "a >= 10" and "a < 100" Otherwise, False
\|\|	(a == 10) \|\| (a == 100)	True if "a == 10" or "a == 100" Otherwise, False
!	!(a == 10)	True if not "a == 10" Otherwise, False

Control Structure

if

if(condition A) {
  //Executed if condition A is satisfied.
}

if(condition A) {
  //Executed if condition A is satisfied.
}
else {
  //Executed if condition A is not satisfied.
}

if(condition A) {
  //Executed if condition A is satisfied.
}
else if(condition B) {
  //Executed if condition A is not satisfied and condition B is satisfied.
}
else {
  //Executed if conditions A and B are not satisfied.
}

for

for(initialization; condition; increment) {
  //Repeat while condition is satisfied.
}

while

while(condition) {
  //Repeat while condition is satisfied.
}

do while

do {
  //Always execute once, then Repeatedly executed while condition is satisfied.
} while(condition);

switch case

switch(variable) {
  case constant1:
    //Execute if variable is 1.
    break;
  case constant2:
    //Execute if variable is 2.
    break;
  case constant3:
    //Execute if variable is 3.
    break;
  default:
    //Execute if all variables do not apply.
}

Standard Functions

The Arduino IDE and Arduino Web Editor provide Arduino standard functions.

The following link is to the reference page on the official Arduino Web site. This article summarizes the Arduino standard functions with reference to these information.

Arduino

Digital I/O

Functions	Parameters	Returns	Explanation
void pinMode(pin, mode)	pin: The digital pin number to set mode: INPUT, OUTPUT, or INPUT_PULLUP	None	Configures the pin to be input, output, or pullup
void digitalWrite(pin, value)	pin: The digital pin number to set value: HIGH or LOW	None	Write HIGH or LOW to the digital pin
int digitalRead(pin)	pin: The digital pin number to set	HIGH or LOW	Reads HIGH or LOW from the digital pin

Arduino-Digital I/O Function This article details the use of Arduino's Digital I/O functions. The Digital I/O functions allow the Arduino board to output and input digital signals. For o...

Analog I/O

Functions	Parameters	Returns	Explanation
void analogReference(type)	type: Reference voltage setting	None	Configures the reference voltage for analog input
int analogRead(pin)	pin: The analog pin number to set	10bits: 0 to 1023 12bits: 0 to 4095	Reads the value from the analog pin
void analogWrite(pin, value)	pin: The digital pin number to set value: The duty cycle(0 to 255)	None	Writes an analog value (PWM wave) to the digital pin

Arduino-Analog I/O Function This article details the use of Arduino's Analog I/O functions. Analog I/O functions allow the Arduino board to output or input analog signals. For other Ard...

Advanced I/O

Functions	Parameters	Returns	Explanation
void tone(pin, unsigned int frequency, unsigned long duration)	pin: The digital pin number to set frequency: The frequency of the tone(Hz) duration: The duration of the tone(ms)	None	Generates a square wave
void noTone(pin)	pin: The digital pin number to set	None	Stops the generation of a square wave
unsigned long pulseInLong(pin, value, unsigned long timeout)	pin: The digital pin number to set value: Type of pulse to read(HIGH or LOW) timeout: Timeout time(us)	The length of the pulse(us)	Reads the pulse
void shiftOut(dataPin, clockPin, bitOrder, value)	dataPin: The digital pin number to output data clockPin: The digital pin number to output clock bitOrder: Which order to shift out the Bits(MSBFIRST or LSBFIRST) value: 1Byte data to shift out	None	Shift out 1Byte data
byte incoming = shiftIn(dataPin, clockPin, bitOrder)	dataPin: The digital pin number to input data clockPin: The digital pin number to output clock bitOrder: Which order to shift in the Bits(MSBFIRST or LSBFIRST) value: 1Byte data to shift out	Input data(1Byte)	Shifts in 1Byte data 1Bit at a time

Time

Functions	Parameters	Returns	Explanation
void delay(unsigned long ms)	ms: Pause time(ms)	None	Pauses the program for the amount of time(ms)
void delayMicroseconds(unsigned int us)	us: Pause time(us)	None	Pauses the program for the amount of time(us)
unsigned long millis(void)	None	Number of milliseconds(ms) since the program started	Returns the number of milliseconds(ms) since running the program
unsigned long micros(void)	None	Number of microseconds(us) since the program started	Returns the number of microseconds(us) since running the program

Arduino-Time Function This article details the use of the Arduino Time function. The Time function can be used to pause the program for the amount of time or to measure the time s...

Math

Functions	Parameters	Returns	Explanation
min(x, y)	x: The first number y: The second number	The smaller of the two numbers	Calculates the minimum of two numbers
max(x, y)	x: The first number y: The second number	The bigger of the two numbers	Calculates the maximum of two numbers
abs(x)	x: The number	The absolute value	Calculates the absolute value of the number
constrain(x, a, b)	x: The number to constrain a: Minimum value of the range b: Maximum value of the range	The value in the range	Returns the number in the range (Minimum or maximum value of the range if outside the range)
long map(long value, long fromLow, long fromHigh, long toLow, long toHigh)	value: The number to map fromLow: The lower value of the current range fromHigh: The upper value of the current range toLow: The lower value of the target range toHigh: The upper value of the target range	The mapped value	Re-maps the number from one range to another
double pow(float base, float exponent)	base: The base number exponent: The multiplier number	The value of the power multiplied by	Calculates the value of the number raised to the power
double sqrt(x)	x: The number	The value of the square root	Calculates the square root of the number
sq(x)	x: The number	The value of the square for the number	Calculates the square of the number

Arduino-Math Function This article details the use of the Arduino Math function. The Math function can be used to compare numbers, calculate absolute values, powers of magnitude, ...

Trigonometry

Functions	Parameters	Returns	Explanation
double cos(float rad)	rad: The angle in radians(rad)	The cos of the angle	Calculates the cosine of the angle
double sin(float rad)	rad: The angle in radians(rad)	The sin of the angle	Calculates the sine of the angle
double tan(float rad)	rad: The angle in radians(rad)	The tan of the angle	Calculates the tangent of the angle

Arduino-Trigonometry Function This article details the use of Arduino's Trigonometry function. The Trigonometry function can be used to calculate cos, sin, and tan. For other Arduino func...

Random Numbers

Functions	Parameters	Returns	Explanation
void randomSeed(unsigned int seed)	seed: The number to initialize the pseudo-random sequence	None	Initializes the pseudo-random number generator
long random(long max) long random(long min, long max)	min: The lower value of the random value max: The upper value of the random value	The random value	Generates pseudo-random numbers

Arduino-Random Numbers Function This article details the use of the Arduino's Random Numbers function. The Random Numbers function can be used to create a random number sequence and obtain ...

Bits and Bytes

Functions	Parameters	Returns	Explanation
uint8_t lowByte(x)	x: The value of any type	The low-order Byte	Extracts the low-order Byte
uint8_t highByte(x)	x: The value of any type	The high-order Byte	Extracts the high-order Byte
boolean bitRead(x, n)	x: The value to read n: Which Bit to read	The value of the Bit	Reads the Bit of the number
void bitWrite(x, n, b)	x: The numeric variable to write n: The Bit of the number to write b: The value to write(0 or 1)	None	Writes the Bit of the numeric variable
void bitSet(x, n)	x: The numeric variable whose Bit to set n: The Bit to set for 1	None	Sets the Bit of the numeric variable for 1
void bitClear(x, n)	x: The numeric variable whose Bit to clear n: The Bit to set for 0	None	Clears the Bit of the numeric variable for 0
bit(n)	n: The Bit whose value to compute	The value of the Bit set to 1	Computes the value of the specified Bit set to 1

Arduino-Bits and Bytes Function This article details the use of the Arduino's Bits and Bytes function. The Bits and Bytes function can be used to manipulate bits and bytes. For other Arduin...

Interrupts

Functions	Parameters	Returns	Explanation
interrupts()	None	None	Enable interrupts
noInterrupts()	None	None	Disable interrupts

External Interrupts

Functions	Parameters	Returns	Explanation
void attachInterrupt(digitalPinToInterrupt(pin), ISR, int mode)	digitalPinToInterrupt(pin): The number of the interrupt ISR: Function at interrupt mode: Interrupt timing	None	Interrupts by pin status
void detachInterrupt(digitalPinToInterrupt(pin))	digitalPinToInterrupt(pin): The number of the interrupt to disable	None	Turns off the given interrupt

Communication/Serial

Functions	Parameters	Returns	Explanation
Serial.begin(unsigned long speed)	speed: Communication speed	None	Initializes serial communication
end()	None	None	Ends serial communication
int Serial.available()	None	The number of bytes available to read	Gets the number of bytes available for reading
int Serial.read()	None	1Byte serial data	Reads 1Byte serial data
int Serial.peek()	None	1Byte serial data	Reads 1Byte serial data without removing it from the buffer
Serial.flush()	None	None	Waits for the transmission of the serial data to complete
Serial.write(data) Serial.write(buf, len)	data: The value to send buf: The array to send len: The number of bytes	Bytes of data to be sent	Data transmission
Serial.print(val, format)	val: The value to print format: Base or Significant Digits	Bytes of data to be sent	Send string (no line feed)
Serial.println(val, format)	val: The value to print format: Base or Significant Digits	Bytes of data to be sent	Send string (with line feed)

Arduino-Communication Function This article details the use of the Arduino's Communication function. Arduino provides standard serial communication functions for easy serial communication....

Standard Libraries

The Arduino IDE and Arduino Web Editor provide Arduino standard libraries.

The following link is to the reference page on the official Arduino Web site. This article summarizes the Arduino standard libraries with reference to these information.

Arduino

EEPROM

Functions	Parameters	Returns	Explanation
byte Read(int address)	int address: Address	1Byte data	Reads 1Byte data from the specified address in EEPROM
void Write(int address, byte value)	int address: Address byte value: 1Byte data	None	Writes 1Byte data at the specified address in EEPROM
int length(void)	None	EEPROM memory size	Gets the EEPROM memory size
void Get(int address, T & data)	int address: Address T &data: Data over 2Bytes	None	Gets 2 or more bytes of data from the specified address in EEPROM
void Put(int address, const T & data)	int address: Address T &data: Data over 2Bytes	None	Writes 2 or more bytes of data at the specified address in EEPROM
void Update(int address, byte value)	int address: Address byte value: 1Byte data	None	Writes 1Byte data at the specified address in EEPROM; if the original data and the write data are the same, the data is not written.
byte EEPROM[int address]	int address: Address	1Byte data	Reads or Writes 1Byte data from the specified address in EEPROM,

Arduino-EEPROM Library This article details the use of the Arduino EEPROM library. The Arduino board is equipped with an EEPROM, a non-volatile memory that can retain data even aft...

Servo

Functions	Parameters	Returns	Explanation
attach(int pin, int min, int max)	int pin: The pin number to attach int min: Pulse width(usec) at angle 0°, Defaults to 544 int max: Pulse width(usec) at angle 180°, Defaults to 2400	Index value	Attach the Servo variable to the pin
bool attached(void)	None	Attached: true Not attached: false	Check whether the Servo variable is attached to the pin
void detach(void)	None	None	Detach the Servo variable from the pin
void write(int angle)	int angle: Specified angle	None	Rotate servo motor to specified angle
void writeMicroseconds(int uS)	int uS: Pulse width in usec	None	Rotate servo motor by specifying pulse width
int read(void)	None	Servo motor angle	Reads the current servo motor angle

Arduino-Servo Library This article details the use of the Servo library in Arduino. The servo motor is operated by a program using "Servo", a library for servo motor control. For ...

Wire(I2C/TWI)

Functions	Parameters	Returns	Explanation
void begin(int address)	int address: Slave address	None	I2C initialization
requestFrom(int address, int quantity, int stop)	int address: Address for I2C device int quantity: The number of bytes to request int stop: "True(1)" will send a stop message after the request "False(0)" will continually send a restart after the request, keeping the connection active	Number of bytes received	Requests data from other I2C devices
void beginTransmission(int address)	int address: Address for I2C device	None	Starts transmitting data to I2C slave
endTransmission(int stop)	int stop: "True(1)" will send a stop message "False(0)" will send a restart, keeping the connection active	Data Transmission Result	Ends of data transmission with I2C slave device
write(value) write(string) write(data, length)	value: 1Byte data string: String data data: Array data length: The number of bytes to transmit	Number of bytes sent	Transmit data to I2C slave device
int available(void)	None	Number of readable bytes	Check the number of bytes available for reading
int read(void)	None	Number of bytes received	Check the number of bytes received

SPI

Functions	Parameters	Returns	Explanation
void begin(void)	None	None	Initializes the SPI bus
void end(void)	None	None	Disables the SPI bus
void beginTransaction(mySettings)	mySettings: SPI speed, bit order, data mode	None	Initializes the SPI bus (Using SPISettings)
void endTransaction(void)	None	None	Ends SPI bus
void setBitOrder(order)	order: LSBFIRST or MSBFIRST	None	Sets SPI bit order
void setClockDivider(divider)	divider: SPI_CLOCK_DIV2 SPI_CLOCK_DIV4 SPI_CLOCK_DIV8 SPI_CLOCK_DIV16 SPI_CLOCK_DIV32 SPI_CLOCK_DIV64 SPI_CLOCK_DIV128	None	Sets SPI clock divider
void setDataMode(mode)	mode: SPI_MODE0 SPI_MODE1 SPI_MODE2 SPI_MODE3	None	Sets SPI transfer mode
int transfer(value)	value: 1Byte data	Number of bytes received	Transmits and Receives the data with SPI devices

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