Arduino Programming

Arduino IDE

(Integrated Developer Environment)

Download from www.Arduino.cc

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Allows you to:

• Edit code
• Compile Code
• Run/upload Code
• Download Libraries
• Run example Code

Variables

• Store Info in Program memory

Problem:

How big is the information?

How much memory must be allocated?

What type of variable?

Data is Stored in memory with Bits

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• Flip-Flops(like a switch)
• Two states: 1/0

^ One Byte ^

Reading Binary Numbers:

• Every bit represents one 2^n

N = 0 1 2 3 4 5 6 7

• A bit’s state defines 2^n for that bit
• All bits with 1 state are added
• All bits with 0 state are ignored

1 + 8 + 16 + 32 + 128

= 185

1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255

N = 0 1 2 3 4 5 6 +/-

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1 + 2 + 4 + 8 + 16 + 32 + 64 x +/-

= [-128, 127]

Unsigned Bytes

• All 8 bits can contribute to byte’s magnitude
• Range [0, 255]

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Signed Bytes

• 7 bits can contribute to byte’s magnitude
• Range [-128, 127]
• Default for all data types

The Arduino must know the data type!

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Some examples:

• Byte: [-127, 127] 1 byte
• Unsigned byte: [0, 255] 1 byte
• int: [-32768, 32767] 2 byte
• Unsigned int: [0, 64535] 2 byte
• (There are sometimes 32 bit ints)
• float: some gigantic number(this also allows you to store decimals)
• long: >10x10^20 8 byte

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^often depends on processor^

Arrays

• Grouping of related values (like a list of numbers)
• Variable declared with number of values (to specify memory usage)
• Array denoted with {}

• Values can be accessed with:

value = variable[n];

n = 0 1 2 3 4

Buffer overflow:

• Writing to values that don’t exist:

number = numbers[100];

• This will kill your processor or crash your code

Char:

• One byte
• Holds a number, but ‘char’ says that it is defined by ASCII Table

ASCII Table:

• Number given to characters on keyboard
• 0-255 values

String:

• Array of chars; each value = char variable
• Terminated with a null ‘\0’ value

Booleans

• ‘bool’
• Can be true or false

The Compiler:

• Precompiler
• Compiles the basic stuff
• #define
• Compiler
• Converts code to machine language

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Great for checking mistakes!

Declaring v.s. Defining

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Declaration

• Make a variable exist and allocate memory

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Definition

• Give a variable a value

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Initialize

• Declaration + Definition
• Some fancy stuff idk about (checkout stackoverflow for some try-hards on this)

void setup()

• Runs once
• Used to initialize variables + libraries
• “void” because it doesn’t return anything

void loop()

• Loops as fast as possible(hardware dependency)

Built-in functions

• Don’t have to be defined because they are built into arduino init library
• Usually are very simple functions

If - else if - Else statement

• Conditional-relies on the state of a variable
• Condition is defined by operators
• Condition is in (), function code in {}
• If code is one line, {} isn’t necessary

While loop

• Conditional-relies on the state of a variable
• Condition is defined by operators
• Loops infinitely until condition = false

For loop

• Loops for a set amount depending on a variable
• Will likely require an operator

Break & continue

• Allow you to control flow of cond. + loops

Switch… case

• Like an if statement, but neater
• Allows you to set a default
• Doesn’t break between cases!!!!!!

Functions

• Return type must be specified
• void - returns nothing
• int -returns an int
• bool, etc.
• Is run by calling it
• Used to simplify complex code-stop handle repetitive tasks

Global Variables

• Declared at the top of program
• Accessible over all code (no scope)
• Can become very confusing, and it’s bad habit to use them in functions!

Local Variables

• Inside functions
• Smaller scope (referencing locals outside their scope doesn’t work
• You can use “static” variable type

Analog

• Continuously varying signal
• Life is analog;
• Computers are digital
• Bits
• ADC: analog to digital converter
• UNO: 10-bit ADC
• 0-1023 values
• Use this to read potentiometers!

Libraries

• A lot of code used to perform specific functions on objects
• Uses object-oriented programming
• Use examples! Be lazy!

TinkerCad challenge:

GOAL:

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Read 2 potentiometers as analog in values (A0-A5 pins) and print their mapped data (from a value 0-1023 to 0-180) to the lcd display every x milliseconds.

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Use functions!

Useful built-in functions:

TinkerCad Challenge Answer:

Structures

• Allow you to create variables that hold other variables
• Is a “type” like int/bool/byte/float
• Arrays of structures allow you to group similar struct variables

Cars

Car: Roadster

Car: Prius

Pointers

• All variables have an address in memory - where they are
• Setting variables equal to others’ addresses makes them “point” to the other’s value
• Allow you to modify global values with local variables!

I2C (I²C) Protocol

• Up to 127 devices
• Master/Slave, Primary/Secondary
• Devices have identification addresses
• 2 wires: SDA (data) and SCL (clock)
• These pins are hardware dependent
• Clock allows devices to read/write at the same rate
• Wire.h library in arduino
• Needs pull-up resistors

PWM protocol

• Pulse-Width-Modulation (square wave) -not exactly a protocol because all protocols use this
• Used to interface with motors (most of the time)
• Requires a PWM pin

SPI protocol

• Max 4 devices
• Master/Slave, Primary/Secondary
• Devices have identification addresses
• 4 wires: MOSI, MISO, SS/CS, SCK
• MOSI: Master-out, slave-in
• MISO: Master-in, slave-out
• SS/CS: Slave/Chip select
• SCK: clock

PWM protocol

• Pulse-Width-Modulation (square wave) -not exactly a protocol because all protocols use this
• Used to interface with motors (most of the time)
• Requires a PWM pin

SPI protocol

• Max 4 devices
• Master/Slave, Primary/Secondary
• Devices have identification addresses
• 4 wires: MOSI, MISO, SS/CS, SCK
• MOSI: Master-out, slave-in
• MISO: Master-in, slave-out
• SS/CS: Slave/Chip select
• SCK: clock