C for Arduino

A sequence of simple sketches for illustrating the C programming language on the Arduino.

The most basic sketch:

/* Pin 13 has an LED connected on most Arduino boards.
   give it a name:  */

int LEDPIN = 13;

// the setup routine runs once when you press reset:
void setup() {  
    pinMode(LEDPIN, OUTPUT);
}

// initialize the digital pin as an output.
void loop() {  
    digitalWrite(LEDPIN, HIGH);
}

Testing with if:

int LEDPIN = 13;

void setup() {  
    pinMode(LEDPIN, OUTPUT);
}

int b = 1;

void loop() {  
    if (b < 10) {
        digitalWrite(LEDPIN, HIGH);
    }

    else {
        digitalWrite(LEDPIN, LOW);
    }
}

Saving state with a variable:

void setup() {  
    pinMode(LEDPIN, OUTPUT);
}

int b = 1;

void loop() {  
    if (b == 1) {
        digitalWrite(LEDPIN, HIGH);
        b = 0;
    }

    else {
        digitalWrite(LEDPIN, LOW);
        b = 1;
    }

    delay(500);
}

Looping with while:

int LEDPIN = 13;

void setup() {
    pinMode(LEDPIN, OUTPUT);
}

void loop() {
    int foo = 0;

    while (foo < 3)
    {
        digitalWrite(LEDPIN, HIGH);
        delay(500);

        digitalWrite(LEDPIN, LOW);
        delay(500);

        foo = foo + 1;
    }

    delay(2000);
}

Looping with for:

int LEDPIN = 13;

void setup() {
    pinMode(LEDPIN, OUTPUT);
}

void loop() {
    int foo;

    for (foo = 0; foo < 3; foo = foo + 1)
    {
        digitalWrite(LEDPIN, HIGH);
        delay(500);

        digitalWrite(LEDPIN, LOW);
        delay(500);
    }

    delay(2000);
}

Defining a function:

int LEDPIN = 13;

void setup() {
    pinMode(LEDPIN, OUTPUT);
}

void blink_led(int number_blinks) {
    int i;

    for (i = 0; i < number_blinks; i++) {
        digitalWrite(LEDPIN, HIGH);
        delay(500);

        digitalWrite(LEDPIN, LOW);
        delay(500);
    }
}

void loop() {
    blink_led(3);
    delay(2000);
}

Using C++ objects:

void setup()
{
    Serial.begin(19200);
    Serial.println("we are in setup");
}

void loop()
{
    Serial.println("we are in loop");
    delay(2000);
}

Using datatypes like float, and putting it all together:

/*
  simplesketch #1e - using datatypes (like float)

  This series of sketches demonstrates some aspects of C/C++ programming on Arduino

  This sketch reads a value from an analog pin, and converts it to a floating point
  number between 0.0 and 1.0.
  This demonstrates the use of "int" and "float" datatypes.

  Hardware setup:

  An Arduino connected to your computer.
  A 10K potentiometer wired so that the middle pin goes to analog pin 4,
  the top pin goes to +5 volts and the bottom pin to GND.

  Revision history:
  - apr 24, 2014 - rolf
    created.

  Author: Rolf Widenfelt (c) 2014 - Some Rights Reserved.

  Note: This source code is licensed under a Creative Commons License, CC-by-sa.
     (attribution, share-alike)
         See http://creativecommons.org/licenses/by-sa/4.0/ for details.
*/

// this defines the analog pin to use
const int SENSORPIN = A4;

// the setup routine runs once
void setup() {

  // set the baud rate
  Serial.begin(19200);
}

// the loop routine runs over and over
void loop() {
  int sensor;      // the sensor value, as an integer
  float sum, avg;  // the sum and average, as floating point values

  // we read the analog pin 5 times, convert to "float", and take the average

  sum = 0.0;
  for (int i = 0; i < 5; i++) {
    sensor = analogRead(SENSORPIN);  // returns a value from 0 to 1023
    sum = sum + sensor;       // Collect new value from sensor in sum.

    Serial.print(sensor);
    Serial.print(" ");

    delay(10);
  }
  Serial.println("");

  avg = sum/5.0;           // calculate the average
  Serial.println(avg);

  delay(2000);
}