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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Conversion > Intcast int() [Conversion] Description Converts a value to the int data type. Syntax int(x) (int)x (C-style type conversion) Parameters x: a value. Allowed data types: any type. Returns Data type: int. See also LANGUAGE int
https://www.arduino.cc/reference/en/language/variables/conversion/intcast/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Conversion > Charcast char() [Conversion] Description Converts a value to the char data type. Syntax char(x) (char)x (C-style type conversion) Parameters x: a value. Allowed data types: any type. Returns Data type: char. See also LANGUAGE char
https://www.arduino.cc/reference/en/language/variables/conversion/charcast/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Conversion > Unsignedlongcast (unsigned long) [Conversion] Description Converts a value to the unsigned long data type. Syntax (unsigned long)x Parameters x: a value of any type Returns unsigned long See also LANGUAGE unsigned long
https://www.arduino.cc/reference/en/language/variables/conversion/unsignedlongcast/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Conversion > Floatcast float() [Conversion] Description Converts a value to the float data type. Syntax float(x) (float)x (C-style type conversion) Parameters x: a value. Allowed data types: any type. Returns Data type: float. Notes and Warnings
https://www.arduino.cc/reference/en/language/variables/conversion/floatcast/index.html
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Returns Data type: float. Notes and Warnings See the reference for float for details about the precision and limitations of floating point numbers on Arduino. See also LANGUAGE float
https://www.arduino.cc/reference/en/language/variables/conversion/floatcast/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Conversion > Longcast long() [Conversion] Description Converts a value to the long data type. Syntax long(x) (long)x (C-style type conversion) Parameters x: a value. Allowed data types: any type. Returns Data type: long. See also LANGUAGE long
https://www.arduino.cc/reference/en/language/variables/conversion/longcast/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Conversion > Unsignedintcast (unsigned int) [Conversion] Description Converts a value to the unsigned int data type. Syntax (unsigned int)x Parameters x: a value of any type Returns unsigned int See also LANGUAGE unsigned int
https://www.arduino.cc/reference/en/language/variables/conversion/unsignedintcast/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > String string [Data Types] Description
https://www.arduino.cc/reference/en/language/variables/data-types/string/index.html
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> String string [Data Types] Description Text strings can be represented in two ways. you can use the String data type, which is part of the core as of version 0019, or you can make a string out of an array of type char and null-terminate it. This page described the latter method. For more details on the String object, which gives you more functionality at the cost of more memory, see the String object page. Syntax All of the following are valid declarations for strings. char Str1[15]; char Str2[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o'}; char Str3[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o', '\0'}; char Str4[] = "arduino";
https://www.arduino.cc/reference/en/language/variables/data-types/string/index.html
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char Str4[] = "arduino"; char Str5[8] = "arduino"; char Str6[15] = "arduino"; Possibilities for declaring strings Declare an array of chars without initializing it as in Str1 Declare an array of chars (with one extra char) and the compiler will add the required null character, as in Str2 Explicitly add the null character, Str3 Initialize with a string constant in quotation marks; the compiler will size the array to fit the string constant and a terminating null character, Str4 Initialize the array with an explicit size and string constant, Str5 Initialize the array, leaving extra space for a larger string, Str6 Null termination Generally, strings are terminated with a null character (ASCII code 0). This allows functions (like Serial.print()) to tell where the end of a string is. Otherwise, they would continue reading subsequent bytes of memory that aren’t actually part of the string.
https://www.arduino.cc/reference/en/language/variables/data-types/string/index.html
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This means that your string needs to have space for one more character than the text you want it to contain. That is why Str2 and Str5 need to be eight characters, even though "arduino" is only seven - the last position is automatically filled with a null character. Str4 will be automatically sized to eight characters, one for the extra null. In Str3, we’ve explicitly included the null character (written '\0') ourselves. Note that it’s possible to have a string without a final null character (e.g. if you had specified the length of Str2 as seven instead of eight). This will break most functions that use strings, so you shouldn’t do it intentionally. If you notice something behaving strangely (operating on characters not in the string), however, this could be the problem. Single quotes or double quotes? Strings are always defined inside double quotes ("Abc") and characters are always defined inside single quotes('A').
https://www.arduino.cc/reference/en/language/variables/data-types/string/index.html
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Wrapping long strings You can wrap long strings like this: char myString[] = "This is the first line" " this is the second line" " etcetera"; Arrays of strings It is often convenient, when working with large amounts of text, such as a project with an LCD display, to setup an array of strings. Because strings themselves are arrays, this is actually an example of a two-dimensional array. In the code below, the asterisk after the datatype char “char*” indicates that this is an array of “pointers”. All array names are actually pointers, so this is required to make an array of arrays. Pointers are one of the more esoteric parts of C++ for beginners to understand, but it isn’t necessary to understand pointers in detail to use them effectively here. Example Code
https://www.arduino.cc/reference/en/language/variables/data-types/string/index.html
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Example Code char *myStrings[] = {"This is string 1", "This is string 2", "This is string 3", "This is string 4", "This is string 5", "This is string 6" }; void setup() { Serial.begin(9600); } void loop() { for (int i = 0; i < 6; i++) { Serial.println(myStrings[i]); delay(500); } } See also LANGUAGE PROGMEM
https://www.arduino.cc/reference/en/language/variables/data-types/string/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Void void [Data Types] Description The void keyword is used only in function declarations. It indicates that the function is expected to return no information to the function from which it was called. Example Code The code shows how to use void. // actions are performed in the functions "setup" and "loop"
https://www.arduino.cc/reference/en/language/variables/data-types/void/index.html
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// actions are performed in the functions "setup" and "loop" // but no information is reported to the larger program void setup() { // ... } void loop() { // ... } See also LANGUAGE Integer Constants
https://www.arduino.cc/reference/en/language/variables/data-types/void/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Int int [Data Types] Description Integers are your primary data-type for number storage.
https://www.arduino.cc/reference/en/language/variables/data-types/int/index.html
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Description Integers are your primary data-type for number storage. On the Arduino Uno (and other ATmega based boards) an int stores a 16-bit (2-byte) value. This yields a range of -32,768 to 32,767 (minimum value of -2^15 and a maximum value of (2^15) - 1). On the Arduino Due and SAMD based boards (like MKR1000 and Zero), an int stores a 32-bit (4-byte) value. This yields a range of -2,147,483,648 to 2,147,483,647 (minimum value of -2^31 and a maximum value of (2^31) - 1).
https://www.arduino.cc/reference/en/language/variables/data-types/int/index.html
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int’s store negative numbers with a technique called (2’s complement math). The highest bit, sometimes referred to as the "sign" bit, flags the number as a negative number. The rest of the bits are inverted and 1 is added. The Arduino takes care of dealing with negative numbers for you, so that arithmetic operations work transparently in the expected manner. There can be an unexpected complication in dealing with the bitshift right operator (>>) however. Syntax int var = val; Parameters var: variable name. val: the value you assign to that variable. Example Code This code creates an integer called 'countUp', which is initially set as the number 0 (zero). The variable goes up by 1 (one) each loop, being displayed on the serial monitor. int countUp = 0; //creates a variable integer called 'countUp' void setup() {
https://www.arduino.cc/reference/en/language/variables/data-types/int/index.html
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void setup() { Serial.begin(9600); // use the serial port to print the number } void loop() { countUp++; //Adds 1 to the countUp int on every loop Serial.println(countUp); // prints out the current state of countUp delay(1000); } Notes and Warnings When signed variables are made to exceed their maximum or minimum capacity they overflow. The result of an overflow is unpredictable so this should be avoided. A typical symptom of an overflow is the variable "rolling over" from its maximum capacity to its minimum or vice versa, but this is not always the case. If you want this behavior, use unsigned int. See also LANGUAGE Integer Constants
https://www.arduino.cc/reference/en/language/variables/data-types/int/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Word word [Data Types] Description A word can store an unsigned number of at least 16 bits (from 0 to 65535). Syntax word var = val; Parameters var: variable name. val: the value to assign to that variable. Example Code
https://www.arduino.cc/reference/en/language/variables/data-types/word/index.html
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var: variable name. val: the value to assign to that variable. Example Code word w = 10000; See also
https://www.arduino.cc/reference/en/language/variables/data-types/word/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Float float [Data Types] Description
https://www.arduino.cc/reference/en/language/variables/data-types/float/index.html
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> Float float [Data Types] Description Datatype for floating-point numbers, a number that has a decimal point. Floating-point numbers are often used to approximate analog and continuous values because they have greater resolution than integers. Floating-point numbers can be as large as 3.4028235E+38 and as low as -3.4028235E+38. They are stored as 32 bits (4 bytes) of information. Syntax float var = val; Parameters var: variable name. val: the value you assign to that variable. Example Code float myfloat; float sensorCalbrate = 1.117; int x; int y; float z; x = 1; y = x / 2; // y now contains 0, ints can't hold fractions
https://www.arduino.cc/reference/en/language/variables/data-types/float/index.html
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z = (float)x / 2.0; // z now contains .5 (you have to use 2.0, not 2) Notes and Warnings If doing math with floats, you need to add a decimal point, otherwise it will be treated as an int. See the Floating point constants page for details. The float data type has only 6-7 decimal digits of precision. That means the total number of digits, not the number to the right of the decimal point. Unlike other platforms, where you can get more precision by using a double (e.g. up to 15 digits), on the Arduino, double is the same size as float. Floating point numbers are not exact, and may yield strange results when compared. For example 9.0 / 0.3 may not quite equal 30.0. You should instead check that the absolute value of the difference between the numbers is less than some small number.
https://www.arduino.cc/reference/en/language/variables/data-types/float/index.html
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Conversion from floating point to integer math results in truncation: float x = 2.9; // A float type variable int y = x; // 2 If, instead, you want to round off during the conversion process, you need to add 0.5: float x = 2.9; int y = x + 0.5; // 3 or use the round() function: float x = 2.9; int y = round(x); // 3 Floating point math is also much slower than integer math in performing calculations, so should be avoided if, for example, a loop has to run at top speed for a critical timing function. Programmers often go to some lengths to convert floating point calculations to integer math to increase speed. See also
https://www.arduino.cc/reference/en/language/variables/data-types/float/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Long long [Data Types] Description Long variables are extended size variables for number storage, and store 32 bits (4 bytes), from -2,147,483,648 to 2,147,483,647.
https://www.arduino.cc/reference/en/language/variables/data-types/long/index.html
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If doing math with integers at least one of the values must be of type long, either an integer constant followed by an L or a variable of type long, forcing it to be a long. See the Integer Constants page for details. Syntax long var = val; Parameters var: variable name. val: the value assigned to the variable. Example Code long speedOfLight_km_s = 300000L; // see the Integer Constants page for explanation of the 'L' See also LANGUAGE Integer Constants
https://www.arduino.cc/reference/en/language/variables/data-types/long/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Boolean boolean [Data Types] Description boolean is a non-standard type alias for bool defined by Arduino. It’s recommended to instead use the standard type bool, which is identical. See also
https://www.arduino.cc/reference/en/language/variables/data-types/boolean/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Bool bool [Data Types] Description A bool holds one of two values, true or false. (Each bool variable occupies one byte of memory.) Syntax bool var = val; Parameters var: variable name. val: the value to assign to that variable. Example Code
https://www.arduino.cc/reference/en/language/variables/data-types/bool/index.html
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var: variable name. val: the value to assign to that variable. Example Code This code shows how to use the bool datatype. int LEDpin = 5; // LED on pin 5 int switchPin = 13; // momentary switch on 13, other side connected to ground bool running = false; void setup() { pinMode(LEDpin, OUTPUT); pinMode(switchPin, INPUT); digitalWrite(switchPin, HIGH); // turn on pullup resistor } void loop() { if (digitalRead(switchPin) == LOW) { // switch is pressed - pullup keeps pin high normally delay(100); // delay to debounce switch running = !running; // toggle running variable digitalWrite(LEDpin, running); // indicate via LED } } See also LANGUAGE constants
https://www.arduino.cc/reference/en/language/variables/data-types/bool/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Stringobject String() [Data Types] Description Constructs an instance of the String class. There are multiple versions that construct Strings from different data types (i.e. format them as sequences of characters), including: a constant string of characters, in double quotes (i.e. a char array)
https://www.arduino.cc/reference/en/language/variables/data-types/stringobject/index.html
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a constant string of characters, in double quotes (i.e. a char array) a single constant character, in single quotes another instance of the String object a constant integer or long integer a constant integer or long integer, using a specified base an integer or long integer variable an integer or long integer variable, using a specified base a float or double, using a specified decimal places Constructing a String from a number results in a string that contains the ASCII representation of that number. The default is base ten, so String thisString = String(13); gives you the String "13". You can use other bases, however. For example, String thisString = String(13, HEX); gives you the String "d", which is the hexadecimal representation of the decimal value 13. Or if you prefer binary, String thisString = String(13, BIN);
https://www.arduino.cc/reference/en/language/variables/data-types/stringobject/index.html
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String thisString = String(13, BIN); gives you the String "1101", which is the binary representation of 13. Syntax String(val) String(val, base) String(val, decimalPlaces) Parameters val: a variable to format as a String. Allowed data types: string, char, byte, int, long, unsigned int, unsigned long, float, double. base: (optional) the base in which to format an integral value. decimalPlaces: only if val is float or double. The desired decimal places. Returns An instance of the String class. Example Code All of the following are valid declarations for Strings. String stringOne = "Hello String"; // using a constant String String stringOne = String('a'); // converting a constant char into a String String stringTwo = String("This is a string"); // converting a constant string into a String object
https://www.arduino.cc/reference/en/language/variables/data-types/stringobject/index.html
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String stringOne = String(stringTwo + " with more"); // concatenating two strings String stringOne = String(13); // using a constant integer String stringOne = String(analogRead(0), DEC); // using an int and a base String stringOne = String(45, HEX); // using an int and a base (hexadecimal) String stringOne = String(255, BIN); // using an int and a base (binary) String stringOne = String(millis(), DEC); // using a long and a base String stringOne = String(5.698, 3); // using a float and the decimal places Functions LANGUAGE charAt() LANGUAGE compareTo() LANGUAGE concat() LANGUAGE c_str() LANGUAGE endsWith() LANGUAGE equals() LANGUAGE equalsIgnoreCase() LANGUAGE getBytes() LANGUAGE indexOf() LANGUAGE lastIndexOf() LANGUAGE length() LANGUAGE remove()
https://www.arduino.cc/reference/en/language/variables/data-types/stringobject/index.html
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LANGUAGE indexOf() LANGUAGE lastIndexOf() LANGUAGE length() LANGUAGE remove() LANGUAGE replace() LANGUAGE reserve() LANGUAGE setCharAt() LANGUAGE startsWith() LANGUAGE substring() LANGUAGE toCharArray() LANGUAGE toDouble() LANGUAGE toInt() LANGUAGE toFloat() LANGUAGE toLowerCase() LANGUAGE toUpperCase() LANGUAGE trim() Operators LANGUAGE [] (element access) LANGUAGE + (concatenation) LANGUAGE += (append) LANGUAGE == (comparison) LANGUAGE > (greater than) LANGUAGE >= (greater than or equal to) LANGUAGE < (less than) LANGUAGE <= (less than or equal to) LANGUAGE != (different from) EXAMPLE String Tutorials See also
https://www.arduino.cc/reference/en/language/variables/data-types/stringobject/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Size t size_t [Data Types] Description size_t is a data type capable of representing the size of any object in bytes. Examples of the use of size_t are the return type of sizeof() and Serial.print(). Syntax size_t var = val; Parameters var: variable name.
https://www.arduino.cc/reference/en/language/variables/data-types/size_t/index.html
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Syntax size_t var = val; Parameters var: variable name. val: the value to assign to that variable. See also
https://www.arduino.cc/reference/en/language/variables/data-types/size_t/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Short short [Data Types] Description A short is a 16-bit data-type.
https://www.arduino.cc/reference/en/language/variables/data-types/short/index.html
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Description A short is a 16-bit data-type. On all Arduinos (ATMega and ARM based) a short stores a 16-bit (2-byte) value. This yields a range of -32,768 to 32,767 (minimum value of -2^15 and a maximum value of (2^15) - 1). Syntax short var = val; Parameters var: variable name. val: the value you assign to that variable. Example Code short ledPin = 13 See also LANGUAGE Integer Constants
https://www.arduino.cc/reference/en/language/variables/data-types/short/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Double double [Data Types] Description Double precision floating point number. On the Uno and other ATMEGA based boards, this occupies 4 bytes. That is, the double implementation is exactly the same as the float, with no gain in precision.
https://www.arduino.cc/reference/en/language/variables/data-types/double/index.html
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On the Arduino Due, doubles have 8-byte (64 bit) precision. Syntax double var = val; Parameters var: variable name. val: the value to assign to that variable. Notes and Warnings Users who borrow code from other sources that includes double variables may wish to examine the code to see if the implied precision is different from that actually achieved on ATMEGA based Arduinos. See also
https://www.arduino.cc/reference/en/language/variables/data-types/double/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Unsignedchar unsigned char [Data Types] Description An unsigned data type that occupies 1 byte of memory. Same as the byte datatype. The unsigned char datatype encodes numbers from 0 to 255. For consistency of Arduino programming style, the byte data type is to be preferred. Syntax
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedchar/index.html
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For consistency of Arduino programming style, the byte data type is to be preferred. Syntax unsigned char var = val; Parameters var: variable name. val: the value to assign to that variable. Example Code unsigned char myChar = 240; See also LANGUAGE Serial.println
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedchar/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Unsignedint unsigned int [Data Types] Description
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedint/index.html
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> Unsignedint unsigned int [Data Types] Description On the Uno and other ATMEGA based boards, unsigned ints (unsigned integers) are the same as ints in that they store a 2 byte value. Instead of storing negative numbers however they only store positive values, yielding a useful range of 0 to 65,535 ((2^16) - 1). The Due stores a 4 byte (32-bit) value, ranging from 0 to 4,294,967,295 (2^32 - 1). The difference between unsigned ints and (signed) ints, lies in the way the highest bit, sometimes referred to as the "sign" bit, is interpreted. In the Arduino int type (which is signed), if the high bit is a "1", the number is interpreted as a negative number, and the other 15 bits are interpreted with (2’s complement math). Syntax
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedint/index.html
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Syntax unsigned int var = val; Parameters var: variable name. val: the value you assign to that variable. Example Code unsigned int ledPin = 13; Notes and Warnings When unsigned variables are made to exceed their maximum capacity they "roll over" back to 0, and also the other way around: unsigned int x; x = 0; x = x - 1; // x now contains 65535 - rolls over in neg direction x = x + 1; // x now contains 0 - rolls over Math with unsigned variables may produce unexpected results, even if your unsigned variable never rolls over. The MCU applies the following rules: The calculation is done in the scope of the destination variable. E.g. if the destination variable is signed, it will do signed math, even if both input variables are unsigned.
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedint/index.html
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However with a calculation which requires an intermediate result, the scope of the intermediate result is unspecified by the code. In this case, the MCU will do unsigned math for the intermediate result, because both inputs are unsigned! unsigned int x = 5; unsigned int y = 10; int result; result = x - y; // 5 - 10 = -5, as expected result = (x - y) / 2; // 5 - 10 in unsigned math is 65530! 65530/2 = 32765 // solution: use signed variables, or do the calculation step by step. result = x - y; // 5 - 10 = -5, as expected result = result / 2; // -5/2 = -2 (only integer math, decimal places are dropped) Why use unsigned variables at all?
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedint/index.html
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Why use unsigned variables at all? The rollover behaviour is desired, e.g. counters The signed variable is a bit too small, but you want to avoid the memory and speed loss of long/float. See also LANGUAGE Integer Constants
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedint/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Char char [Data Types] Description A data type used to store a character value. Character literals are written in single quotes, like this: 'A' (for multiple characters - strings - use double quotes: "ABC").
https://www.arduino.cc/reference/en/language/variables/data-types/char/index.html
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Characters are stored as numbers however. You can see the specific encoding in the ASCII chart. This means that it is possible to do arithmetic on characters, in which the ASCII value of the character is used (e.g. 'A' + 1 has the value 66, since the ASCII value of the capital letter A is 65). See Serial.println reference for more on how characters are translated to numbers. The size of the char datatype is at least 8 bits. It’s recommended to only use char for storing characters. For an unsigned, one-byte (8 bit) data type, use the byte data type. Syntax char var = val; Parameters var: variable name. val: the value to assign to that variable. Example Code char myChar = 'A'; char myChar = 65; // both are equivalent See also LANGUAGE Serial.println
https://www.arduino.cc/reference/en/language/variables/data-types/char/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Byte byte [Data Types] Description A byte stores an 8-bit unsigned number, from 0 to 255. Syntax byte var = val; Parameters var: variable name. val: the value to assign to that variable. See also LANGUAGE byte()
https://www.arduino.cc/reference/en/language/variables/data-types/byte/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Array array [Data Types] Description An array is a collection of variables that are accessed with an index number. Arrays in the C++ programming language Arduino sketches are written in can be complicated, but using simple arrays is relatively straightforward. Creating (Declaring) an Array
https://www.arduino.cc/reference/en/language/variables/data-types/array/index.html
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Creating (Declaring) an Array All of the methods below are valid ways to create (declare) an array. int myInts[6]; int myPins[] = {2, 4, 8, 3, 6}; int mySensVals[5] = {2, 4, -8, 3, 2}; char message[6] = "hello"; You can declare an array without initializing it as in myInts. In myPins we declare an array without explicitly choosing a size. The compiler counts the elements and creates an array of the appropriate size. Finally you can both initialize and size your array, as in mySensVals. Note that when declaring an array of type char, one more element than your initialization is required, to hold the required null character. Accessing an Array
https://www.arduino.cc/reference/en/language/variables/data-types/array/index.html
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Accessing an Array Arrays are zero indexed, that is, referring to the array initialization above, the first element of the array is at index 0, hence mySensVals[0] == 2, mySensVals[1] == 4, and so forth. It also means that in an array with ten elements, index nine is the last element. Hence: int myArray[10]={9, 3, 2, 4, 3, 2, 7, 8, 9, 11}; // myArray[9] contains 11 // myArray[10] is invalid and contains random information (other memory address)
https://www.arduino.cc/reference/en/language/variables/data-types/array/index.html
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// myArray[10] is invalid and contains random information (other memory address) For this reason you should be careful in accessing arrays. Accessing past the end of an array (using an index number greater than your declared array size - 1) is reading from memory that is in use for other purposes. Reading from these locations is probably not going to do much except yield invalid data. Writing to random memory locations is definitely a bad idea and can often lead to unhappy results such as crashes or program malfunction. This can also be a difficult bug to track down. Unlike BASIC or JAVA, the C++ compiler does no checking to see if array access is within legal bounds of the array size that you have declared. To assign a value to an array: mySensVals[0] = 10; To retrieve a value from an array: x = mySensVals[4]; Arrays and FOR Loops
https://www.arduino.cc/reference/en/language/variables/data-types/array/index.html
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x = mySensVals[4]; Arrays and FOR Loops Arrays are often manipulated inside for loops, where the loop counter is used as the index for each array element. For example, to print the elements of an array over the serial port, you could do something like this: for (byte i = 0; i < 5; i = i + 1) { Serial.println(myPins[i]); } Example Code For a complete program that demonstrates the use of arrays, see the (How to Use Arrays example) from the (Built-in Examples). See also LANGUAGE PROGMEM
https://www.arduino.cc/reference/en/language/variables/data-types/array/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Data types > Unsignedlong unsigned long [Data Types] Description
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedlong/index.html
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> Unsignedlong unsigned long [Data Types] Description Unsigned long variables are extended size variables for number storage, and store 32 bits (4 bytes). Unlike standard longs unsigned longs won’t store negative numbers, making their range from 0 to 4,294,967,295 (2^32 - 1). Syntax unsigned long var = val; Parameters var: variable name. val: the value you assign to that variable. Example Code unsigned long time; void setup() { Serial.begin(9600); } void loop() { Serial.print("Time: "); time = millis(); //prints time since program started Serial.println(time); // wait a second so as not to send massive amounts of data delay(1000); } See also LANGUAGE Integer Constants
https://www.arduino.cc/reference/en/language/variables/data-types/unsignedlong/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Utilities > Progmem PROGMEM [Utilities] Description Store data in flash (program) memory instead of SRAM. There’s a description of the various types of memory available on an Arduino board.
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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The PROGMEM keyword is a variable modifier, it should be used only with the datatypes defined in pgmspace.h. It tells the compiler "put this information into flash memory", instead of into SRAM, where it would normally go. PROGMEM is part of the pgmspace.h library. It is included automatically in modern versions of the IDE. However, if you are using an IDE version below 1.0 (2011), you’ll first need to include the library at the top of your sketch, like this: #include <avr/pgmspace.h> While PROGMEM could be used on a single variable, it is really only worth the fuss if you have a larger block of data that needs to be stored, which is usually easiest in an array, (or another C++ data structure beyond our present discussion).
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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Using PROGMEM is also a two-step procedure. After getting the data into Flash memory, it requires special methods (functions), also defined in the pgmspace.h library, to read the data from program memory back into SRAM, so we can do something useful with it. Syntax const dataType variableName[] PROGMEM = {data0, data1, data3…​}; Note that because PROGMEM is a variable modifier, there is no hard and fast rule about where it should go, so the Arduino compiler accepts all of the definitions below, which are also synonymous. However, experiments have indicated that, in various versions of Arduino (having to do with GCC version), PROGMEM may work in one location and not in another. The "string table" example below has been tested to work with Arduino 13. Earlier versions of the IDE may work better if PROGMEM is included after the variable name. const dataType variableName[] PROGMEM = {}; // use this form
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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const dataType variableName[] PROGMEM = {}; // use this form const PROGMEM dataType variableName[] = {}; // or this one const dataType PROGMEM variableName[] = {}; // not this one Parameters dataType: Allowed data types: any variable type. variableName: the name for your array of data. Example Code The following code fragments illustrate how to read and write unsigned chars (bytes) and ints (2 bytes) to PROGMEM. // save some unsigned ints const PROGMEM uint16_t charSet[] = { 65000, 32796, 16843, 10, 11234}; // save some chars const char signMessage[] PROGMEM = {"I AM PREDATOR, UNSEEN COMBATANT. CREATED BY THE UNITED STATES DEPART"}; unsigned int displayInt; char myChar; void setup() { Serial.begin(9600);
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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char myChar; void setup() { Serial.begin(9600); while (!Serial); // wait for serial port to connect. Needed for native USB // put your setup code here, to run once: // read back a 2-byte int for (byte k = 0; k < 5; k++) { displayInt = pgm_read_word_near(charSet + k); Serial.println(displayInt); } Serial.println(); // read back a char for (byte k = 0; k < strlen_P(signMessage); k++) { myChar = pgm_read_byte_near(signMessage + k); Serial.print(myChar); } Serial.println(); } void loop() { // put your main code here, to run repeatedly: } Arrays of strings
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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// put your main code here, to run repeatedly: } Arrays of strings It is often convenient when working with large amounts of text, such as a project with an LCD, to setup an array of strings. Because strings themselves are arrays, this is actually an example of a two-dimensional array. These tend to be large structures so putting them into program memory is often desirable. The code below illustrates the idea. /* PROGMEM string demo How to store a table of strings in program memory (flash), and retrieve them. Information summarized from: http://www.nongnu.org/avr-libc/user-manual/pgmspace.html Setting up a table (array) of strings in program memory is slightly complicated, but here is a good template to follow. Setting up the strings is a two-step process. First, define the strings. */ #include <avr/pgmspace.h>
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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*/ #include <avr/pgmspace.h> const char string_0[] PROGMEM = "String 0"; // "String 0" etc are strings to store - change to suit. const char string_1[] PROGMEM = "String 1"; const char string_2[] PROGMEM = "String 2"; const char string_3[] PROGMEM = "String 3"; const char string_4[] PROGMEM = "String 4"; const char string_5[] PROGMEM = "String 5"; // Then set up a table to refer to your strings. const char *const string_table[] PROGMEM = {string_0, string_1, string_2, string_3, string_4, string_5}; char buffer[30]; // make sure this is large enough for the largest string it must hold void setup() { Serial.begin(9600);
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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void setup() { Serial.begin(9600); while (!Serial); // wait for serial port to connect. Needed for native USB Serial.println("OK"); } void loop() { /* Using the string table in program memory requires the use of special functions to retrieve the data. The strcpy_P function copies a string from program space to a string in RAM ("buffer"). Make sure your receiving string in RAM is large enough to hold whatever you are retrieving from program space. */ for (int i = 0; i < 6; i++) { strcpy_P(buffer, (char *)pgm_read_word(&(string_table[i]))); // Necessary casts and dereferencing, just copy. Serial.println(buffer); delay(500); } } Notes and Warnings
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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delay(500); } } Notes and Warnings Please note that variables must be either globally defined, OR defined with the static keyword, in order to work with PROGMEM. The following code will NOT work when inside a function: const char long_str[] PROGMEM = "Hi, I would like to tell you a bit about myself.\n"; The following code WILL work, even if locally defined within a function: const static char long_str[] PROGMEM = "Hi, I would like to tell you a bit about myself.\n" The F() macro When an instruction like : Serial.print("Write something on the Serial Monitor"); is used, the string to be printed is normally saved in RAM. If your sketch prints a lot of stuff on the Serial Monitor, you can easily fill the RAM. If you have free FLASH memory space, you can easily indicate that the string must be saved in FLASH using the syntax:
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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Serial.print(F("Write something on the Serial Monitor that is stored in FLASH")); See also EXAMPLE Types of memory available on an Arduino board DEFINITION array DEFINITION string
https://www.arduino.cc/reference/en/language/variables/utilities/progmem/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Utilities > Sizeof sizeof() [Utilities] Description The sizeof operator returns the number of bytes in a variable type, or the number of bytes occupied by an array. Syntax sizeof(variable) Parameters
https://www.arduino.cc/reference/en/language/variables/utilities/sizeof/index.html
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Syntax sizeof(variable) Parameters variable: The thing to get the size of. Allowed data types: any variable type or array (e.g. int, float, byte). Returns The number of bytes in a variable or bytes occupied in an array. Data type: size_t. Example Code The sizeof operator is useful for dealing with arrays (such as strings) where it is convenient to be able to change the size of the array without breaking other parts of the program. This program prints out a text string one character at a time. Try changing the text phrase. char myStr[] = "this is a test"; void setup() { Serial.begin(9600); } void loop() { for (byte i = 0; i < sizeof(myStr) - 1; i++) { Serial.print(i, DEC); Serial.print(" = "); Serial.write(myStr[i]);
https://www.arduino.cc/reference/en/language/variables/utilities/sizeof/index.html
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Serial.print(" = "); Serial.write(myStr[i]); Serial.println(); } delay(5000); // slow down the program } Notes and Warnings Note that sizeof returns the total number of bytes. So for arrays of larger variable types such as ints, the for loop would look something like this. int myValues[] = {123, 456, 789}; // this for loop works correctly with an array of any type or size for (byte i = 0; i < (sizeof(myValues) / sizeof(myValues[0])); i++) { // do something with myValues[i] } Note that a properly formatted string ends with the NULL symbol, which has ASCII value 0. See also
https://www.arduino.cc/reference/en/language/variables/utilities/sizeof/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Constants > Integerconstants Integer Constants [Constants] Description Integer constants are numbers that are used directly in a sketch, like 123. By default, these numbers are treated as int but you can change this with the U and L modifiers (see below).
https://www.arduino.cc/reference/en/language/variables/constants/integerconstants/index.html
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Normally, integer constants are treated as base 10 (decimal) integers, but special notation (formatters) may be used to enter numbers in other bases. Base Example Formatter Comment 10 (decimal) 123 none 2 (binary) 0b1111011 leading "0b" characters 0&1 valid 8 (octal) 0173 leading "0" characters 0-7 valid 16 (hexadecimal) 0x7B leading "0x" characters 0-9, A-F, a-f valid Decimal (base 10) This is the common-sense math with which you are acquainted. Constants without other prefixes are assumed to be in decimal format. Example Code: n = 101; // same as 101 decimal ((1 * 10^2) + (0 * 10^1) + 1)
https://www.arduino.cc/reference/en/language/variables/constants/integerconstants/index.html
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Binary (base 2) Only the characters 0 and 1 are valid. Example Code: n = 0b101; // same as 5 decimal ((1 * 2^2) + (0 * 2^1) + 1) Octal (base 8) Only the characters 0 through 7 are valid. Octal values are indicated by the prefix "0" (zero). Example Code: n = 0101; // same as 65 decimal ((1 * 8^2) + (0 * 8^1) + 1) It is possible to generate a hard-to-find bug by (unintentionally) including a leading zero before a constant and having the compiler unintentionally interpret your constant as octal. Hexadecimal (base 16)
https://www.arduino.cc/reference/en/language/variables/constants/integerconstants/index.html
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Hexadecimal (base 16) Valid characters are 0 through 9 and letters A through F; A has the value 10, B is 11, up to F, which is 15. Hex values are indicated by the prefix "0x". Note that A-F may be upper (A-F) or lower case (a-f). Example Code: n = 0x101; // same as 257 decimal ((1 * 16^2) + (0 * 16^1) + 1) Notes and Warnings U & L formatters: By default, an integer constant is treated as an int with the attendant limitations in values. To specify an integer constant with another data type, follow it with: a 'u' or 'U' to force the constant into an unsigned data format. Example: 33u
https://www.arduino.cc/reference/en/language/variables/constants/integerconstants/index.html
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a 'l' or 'L' to force the constant into a long data format. Example: 100000L a 'ul' or 'UL' to force the constant into an unsigned long constant. Example: 32767ul See also
https://www.arduino.cc/reference/en/language/variables/constants/integerconstants/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Constants > Constants constants [Constants] Description Constants are predefined expressions in the Arduino language. They are used to make the programs easier to read. We classify constants in groups: Defining Logical Levels: true and false (Boolean Constants)
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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Defining Logical Levels: true and false (Boolean Constants) There are two constants used to represent truth and falsity in the Arduino language: true, and false. false false is the easier of the two to define. false is defined as 0 (zero). true true is often said to be defined as 1, which is correct, but true has a wider definition. Any integer which is non-zero is true, in a Boolean sense. So -1, 2 and -200 are all defined as true, too, in a Boolean sense. Note that the true and false constants are typed in lowercase unlike HIGH, LOW, INPUT, and OUTPUT. Defining Pin Levels: HIGH and LOW When reading or writing to a digital pin there are only two possible values a pin can take/be-set-to: HIGH and LOW. HIGH
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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HIGH The meaning of HIGH (in reference to a pin) is somewhat different depending on whether a pin is set to an INPUT or OUTPUT. When a pin is configured as an INPUT with pinMode(), and read with digitalRead(), the Arduino (ATmega) will report HIGH if: a voltage greater than 3.0V is present at the pin (5V boards) a voltage greater than 2.0V is present at the pin (3.3V boards) A pin may also be configured as an INPUT with pinMode(), and subsequently made HIGH with digitalWrite(). This will enable the internal 20K pullup resistors, which will pull up the input pin to a HIGH reading unless it is pulled LOW by external circuitry. This can be done alternatively by passing INPUT_PULLUP as argument to the pinMode() function, as explained in more detail in the section "Defining Digital Pins modes: INPUT, INPUT_PULLUP, and OUTPUT" further below.
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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When a pin is configured to OUTPUT with pinMode(), and set to HIGH with digitalWrite(), the pin is at: 5 volts (5V boards) 3.3 volts (3.3V boards) In this state it can source current, e.g. light an LED that is connected through a series resistor to ground. LOW The meaning of LOW also has a different meaning depending on whether a pin is set to INPUT or OUTPUT. When a pin is configured as an INPUT with pinMode(), and read with digitalRead(), the Arduino (ATmega) will report LOW if: a voltage less than 1.5V is present at the pin (5V boards) a voltage less than 1.0V (Approx) is present at the pin (3.3V boards)
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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When a pin is configured to OUTPUT with pinMode(), and set to LOW with digitalWrite(), the pin is at 0 volts (both 5V and 3.3V boards). In this state it can sink current, e.g. light an LED that is connected through a series resistor to +5 volts (or +3.3 volts). Defining Digital Pins modes: INPUT, INPUT_PULLUP, and OUTPUT Digital pins can be used as INPUT, INPUT_PULLUP, or OUTPUT. Changing a pin with pinMode() changes the electrical behavior of the pin. Pins Configured as INPUT Arduino (ATmega) pins configured as INPUT with pinMode() are said to be in a high-impedance state. Pins configured as INPUT make extremely small demands on the circuit that they are sampling, equivalent to a series resistor of 100 Megohms in front of the pin. This makes them useful for reading a sensor.
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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If you have your pin configured as an INPUT, and are reading a switch, when the switch is in the open state the input pin will be "floating", resulting in unpredictable results. In order to assure a proper reading when the switch is open, a pull-up or pull-down resistor must be used. The purpose of this resistor is to pull the pin to a known state when the switch is open. A 10 K ohm resistor is usually chosen, as it is a low enough value to reliably prevent a floating input, and at the same time a high enough value to not draw too much current when the switch is closed. See the Digital Read Serial tutorial for more information. If a pull-down resistor is used, the input pin will be LOW when the switch is open and HIGH when the switch is closed. If a pull-up resistor is used, the input pin will be HIGH when the switch is open and LOW when the switch is closed.
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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Pins Configured as INPUT_PULLUP The ATmega microcontroller on the Arduino has internal pull-up resistors (resistors that connect to power internally) that you can access. If you prefer to use these instead of external pull-up resistors, you can use the INPUT_PULLUP argument in pinMode(). See the Input Pullup Serial tutorial for an example of this in use. Pins configured as inputs with either INPUT or INPUT_PULLUP can be damaged or destroyed if they are connected to voltages below ground (negative voltages) or above the positive power rail (5V or 3V). Pins Configured as OUTPUT
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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Pins Configured as OUTPUT Pins configured as OUTPUT with pinMode() are said to be in a low-impedance state. This means that they can provide a substantial amount of current to other circuits. ATmega pins can source (provide current) or sink (absorb current) up to 40 mA (milliamps) of current to other devices/circuits. This makes them useful for powering LEDs because LEDs typically use less than 40 mA. Loads greater than 40 mA (e.g. motors) will require a transistor or other interface circuitry. Pins configured as outputs can be damaged or destroyed if they are connected to either the ground or positive power rails. Defining built-ins: LED_BUILTIN
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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Defining built-ins: LED_BUILTIN Most Arduino boards have a pin connected to an on-board LED in series with a resistor. The constant LED_BUILTIN is the number of the pin to which the on-board LED is connected. Most boards have this LED connected to digital pin 13. See also
https://www.arduino.cc/reference/en/language/variables/constants/constants/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Variables > Constants > Floatingpointconstants Floating Point Constants [Constants] Description Similar to integer constants, floating point constants are used to make code more readable. Floating point constants are swapped at compile time for the value to which the expression evaluates. Example Code
https://www.arduino.cc/reference/en/language/variables/constants/floatingpointconstants/index.html
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Example Code float n = 0.005; // 0.005 is a floating point constant Notes and Warnings Floating point constants can also be expressed in a variety of scientific notation. 'E' and 'e' are both accepted as valid exponent indicators. floating-point constant evaluates to: also evaluates to: 10.0 10 2.34E5 2.34 * 10^5 234000 67e-12 67.0 * 10^-12 0.000000000067 See also
https://www.arduino.cc/reference/en/language/variables/constants/floatingpointconstants/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Functions > Digital io > Digitalread digitalRead() [Digital I/O] Description Reads the value from a specified digital pin, either HIGH or LOW. Syntax digitalRead(pin) Parameters pin: the Arduino pin number you want to read Returns HIGH or LOW Example Code
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalread/index.html
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pin: the Arduino pin number you want to read Returns HIGH or LOW Example Code Sets pin 13 to the same value as pin 7, declared as an input. 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 } Notes and Warnings
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalread/index.html
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} Notes and Warnings If the pin isn’t connected to anything, digitalRead() can return either HIGH or LOW (and this can change randomly). The analog input pins can be used as digital pins, referred to as A0, A1, etc. The exception is the Arduino Nano, Pro Mini, and Mini’s A6 and A7 pins, which can only be used as analog inputs. See also EXAMPLE Description of the digital pins
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalread/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Functions > Digital io > Digitalwrite digitalWrite() [Digital I/O] Description Write a HIGH or a LOW value to a digital pin.
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalwrite/index.html
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Description Write 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
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalwrite/index.html
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Syntax digitalWrite(pin, value) Parameters pin: the Arduino pin number. value: HIGH or LOW. Returns Nothing Example Code The code makes the digital pin 13 an OUTPUT and toggles it by alternating between HIGH and LOW at one second pace. void setup() { pinMode(13, OUTPUT); // sets the digital pin 13 as output } void loop() { digitalWrite(13, HIGH); // sets the digital pin 13 on delay(1000); // waits for a second digitalWrite(13, LOW); // sets the digital pin 13 off delay(1000); // waits for a second } Notes and Warnings
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalwrite/index.html
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delay(1000); // waits for a second } Notes and Warnings The analog input pins can be used as digital pins, referred to as A0, A1, etc. The exception is the Arduino Nano, Pro Mini, and Mini’s A6 and A7 pins, which can only be used as analog inputs. See also EXAMPLE Description of the digital pins
https://www.arduino.cc/reference/en/language/functions/digital-io/digitalwrite/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Functions > Digital io > Pinmode pinMode() [Digital I/O] Description Configures 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.
https://www.arduino.cc/reference/en/language/functions/digital-io/pinmode/index.html
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As of Arduino 1.0.1, it is possible to enable the internal pullup resistors with the mode INPUT_PULLUP. Additionally, the INPUT mode explicitly disables the internal pullups. Syntax pinMode(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 Nothing Example Code The code makes the digital pin 13 OUTPUT and Toggles it HIGH and LOW void setup() { pinMode(13, OUTPUT); // sets the digital pin 13 as output } void loop() { digitalWrite(13, HIGH); // sets the digital pin 13 on delay(1000); // waits for a second digitalWrite(13, LOW); // sets the digital pin 13 off
https://www.arduino.cc/reference/en/language/functions/digital-io/pinmode/index.html
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digitalWrite(13, LOW); // sets the digital pin 13 off delay(1000); // waits for a second } Notes and Warnings The analog input pins can be used as digital pins, referred to as A0, A1, etc. See also EXAMPLE Description of the digital pins
https://www.arduino.cc/reference/en/language/functions/digital-io/pinmode/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Functions > Bits and bytes > Highbyte highByte() [Bits and Bytes] Description Extracts the high-order (leftmost) byte of a word (or the second lowest byte of a larger data type). Syntax highByte(x) Parameters x: a value of any type Returns Data type: byte.
https://www.arduino.cc/reference/en/language/functions/bits-and-bytes/highbyte/index.html
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Parameters x: a value of any type Returns Data type: byte. See also LANGUAGE word()
https://www.arduino.cc/reference/en/language/functions/bits-and-bytes/highbyte/index.html
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Language functions variables structure Libraries IoT Cloud API Glossary The Arduino Reference text is licensed under a Creative Commons Attribution-Share Alike 3.0 License. Find anything that can be improved? Suggest corrections and new documentation via GitHub. Doubts on how to use Github? Learn everything you need to know in this tutorial. Last Revision: Searching... Last Build: 2023/06/30 Edit This Page Reference > Language > Functions > Bits and bytes > Bitread bitRead() [Bits and Bytes] Description Reads a bit of a number. Syntax bitRead(x, n) Parameters x: the number from which to read. n: which bit to read, starting at 0 for the least-significant (rightmost) bit.
https://www.arduino.cc/reference/en/language/functions/bits-and-bytes/bitread/index.html