Arduino Code

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Basic Language Reference

1. Digital I/O

int ledPin = 13;  // LED connected to digital pin 13
int inPin = 7;    // pushbutton connected to digital pin 7
int val = 0;      // variable to store the read value

void setup() {
  pinMode(ledPin, OUTPUT);  // sets the digital pin 13 as output
  pinMode(inPin, INPUT);    // sets the digital pin 7 as input
}

void loop() {
  val = digitalRead(inPin);   // read the input pin
  digitalWrite(ledPin, val);  // sets the LED to the button's value
}

1.1 digitalRead()
- Description: Reads the value from a specified digital pin, either HIGH or LOW.
- Syntax
  (pin)
- Parameters(pin): the Arduino pin number you want to read
- Returns
  or LOW
- Example Code(Sets pin 13 to the same value as pin 7, declared as an input.)
1.2 digitalWrite()
- Description
  a HIGH or a LOW value to a digital pin.If the pin has been configured as an OUTPUT with pinMode(), its voltage will be set to the corresponding value: 5V (or 3.3V on 3.3V boards) for HIGH, 0V (ground) for LOW.If the pin is configured as an INPUT, digitalWrite() will enable (HIGH) or disable (LOW) the internal pullup on the input pin. It is recommended to set the pinMode() to INPUT_PULLUP to enable the internal pull-up resistor. See the Digital Pins tutorial for more information.If you do not set the pinMode() to OUTPUT, and connect an LED to a pin, when calling digitalWrite(HIGH), the LED may appear dim. Without explicitly setting pinMode(), digitalWrite() will have enabled the internal pull-up resistor, which acts like a large current-limiting resistor.
- Syntax: digitalWrite(pin, value)
- Parameters:
  - pin: the Arduino pin number.
  - value: HIGH or LOW.
- Returns
- Example Code
  code makes the digital pin 13 an OUTPUT and toggles it by alternating between HIGH and LOW at one second pace.
1.3 pinMode()
- Description
  the specified pin to behave either as an input or an output. See the Digital Pins page for details on the functionality of the pins.
- Syntax
  (pin, mode)
- Parameters
  - pin: the Arduino pin number to set the mode of.
  - mode: INPUT, OUTPUT, or INPUT_PULLUP. See the Digital Pins page for a more complete description of the functionality.
- Returns

2 Analog I/O

2.1 analogRead(pin)
- Example Code
  code reads the voltage on analogPin and displays it.
```
int analogPin = A3; // potentiometer wiper (middle terminal) connected to analog pin 3
                  // outside leads to ground and +5V
int val = 0;  // variable to store the value read

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

void loop() {
val = analogRead(analogPin);  // read the input pin
Serial.println(val);          // debug value
}
```
- Description: Reads the value from the specified analog pin. Arduino boards contain a multichannel, 10-bit analog to digital converter. This means that it will map input voltages between 0 and the operating voltage(5V or 3.3V) into integer values between 0 and 1023. On an Arduino UNO, for example, this yields a resolution between readings of: 5 volts / 1024 units or, 0.0049 volts (4.9 mV) per unit. See the table below for the usable pins, operating voltage and maximum resolution for some Arduino boards.The input range can be changed using analogReference(), while the resolution can be changed (only for Zero, Due and MKR boards) using analogReadResolution().On ATmega based boards (UNO, Nano, Mini, Mega), it takes about 100 microseconds (0.0001 s) to read an analog input, so the maximum reading rate is about 10,000 times a second.
- Syntax
  (pin)
- Parameters:pin: the name of the analog input pin to read from (A0 to A5 on most boards, A0 to A6 on MKR boards, A0 to A7 on the Mini and Nano, A0 to A15 on the Mega).
- Returns
  analog reading on the pin. Although it is limited to the resolution of the analog to digital converter (0-1023 for 10 bits or 0-4095 for 12 bits). Data type: int.
2.2 analogWrite(pin)
- Description
  an analog value (PWM wave) to a pin. Can be used to light a LED at varying brightnesses or drive a motor at various speeds. After a call to analogWrite(), the pin will generate a steady rectangular wave of the specified duty cycle until the next call to analogWrite() (or a call to digitalRead() or digitalWrite()) on the same pin.
- Syntax
  (pin, value)
- Parameters:pin: the Arduino pin to write to. Allowed data types: int.
- value: the duty cycle: between 0 (always off) and 255 (always on). Allowed data types: int.
- Returns
- Example Code
  the output to the LED proportional to the value read from the potentiometer.
```
int ledPin = 9;      // LED connected to digital pin 9
int analogPin = 3;   // potentiometer connected to analog pin 3
int val = 0;         // variable to store the read value

void setup() {
pinMode(ledPin, OUTPUT);  // sets the pin as output
}

void loop() {
val = analogRead(analogPin);  // read the input pin
analogWrite(ledPin, val / 4); // analogRead values go from 0 to 1023, analogWrite values from 0 to 255
}
```

3. Math

3.1 abs()
- Description
  the absolute value of a number.
- Syntax
  (x)
- Parameters x: the number
- Returns:
  - x: if x is greater than or equal to 0.
  - -x: if x is less than 0.
3.2 constrain()
- Description
  a number to be within a range.
- Syntax
  (x, a, b)
- Parameters
  - x: the number to constrain Allowed data types: all data types.
  - a: the lower end of the range. Allowed data types: all data types.
  - b: the upper end of the range. Allowed data types: all data types.
- Returns
  - x: if x is between a and b.
  - a: if x is less than a.
  - b: if x is greater than b.
- Example Code
  code limits the sensor values to between 10 to 150.
```
sensVal = constrain(sensVal, 10, 150); 
// limits range of sensor values to between 10 and 150
```
3.3 max()/min()
- Description
  the maximum( minimum) of two numbers.
- Syntax
  (x, y) /min(x,y)
- Parameters
  - x: the first number. Allowed data types: any data type.
  - y: the second number. Allowed data types: any data type.
- Returns
  - max
    larger of the two parameter values.
  - min
    larger of the two parameter values.
- Example Code
  code ensures that sensVal is at least 20.
```
sensVal = max(sensVal, 20);
// assigns sensVal to the larger of sensVal or 20
```
3.4 pow()
- Description
  the value of a number raised to a power. pow() can be used to raise a number to a fractional power. This is useful for generating exponential mapping of values or curves.
- Syntax
  (base, exponent)
- Parameters
  - base: the number. Allowed data types: float.
  - exponent: the power to which the base is raised. Allowed data types: float.
- Returns
  result of the exponentiation. Data type: double.
- Example Code
  the value of x raised to
z = pow(x, y);
3.5 sq()
- Description
  the square of a number: the number multiplied by itself.
- Syntax
  (x)
- Parameters x: the number. Allowed data types: any data type.
- Returns
  square of the number. Data type: double.
3.6 sqrt()
- Description
  the square root of a number.
- Syntax
  (x)
- Parameters x: the number. Allowed data types: any data type.
- Returns
  number’s square root. Data type: double.

4. Random Numbers

Description
random function generates pseudo-random numbers.
Syntax
- random(max)
- random(min, max)
Parameters
- min: lower bound of the random value, inclusive (optional).
- max: upper bound of the random value, exclusive.
Returns
random number between min and max-1. Data type: long.

5. Communication

5.1 Serial.begin()
```
void setup() {
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {}
```
Description
the data rate in bits per second (baud) for serial data transmission. For communicating with Serial Monitor, make sure to use one of the baud rates listed in the menu at the bottom right corner of its screen. 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.

5.2 Serial.write()

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.
}

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.

5.3 Serial.print()

Description

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.

Serial.print(78)

Result

“78”

6. Time

delay()
Description
the program for the amount of time (in milliseconds) specified as parameter. (There are 1000 milliseconds in a second.)
Syntax
(ms)
Parameters: ms: the number of milliseconds to pause. Allowed data types: unsigned long.
Returns

Example Code

code pauses the program for one second before toggling the output pin.

int ledPin = 13;              // LED connected to digital pin 13

void setup() {
  pinMode(ledPin, OUTPUT);    // sets the digital pin as output 
}

void loop() {
  digitalWrite(ledPin, HIGH); // sets the LED on
  delay(1000);                // waits for a second
  digitalWrite(ledPin, LOW);  // sets the LED off
  delay(1000);                // waits for a second
}

we can also use the following 3 commands

delayMicroseconds()
micros()
millis()