if / else-condition
Use of if
To understand the meaning of if, let's take a look at the program code for the following example:
If you want to light an LED depending on a switch, the code would look like this:
if (digitalRead(BUTTON_PIN) == HIGH) {
digitalWrite(LED_PIN, HIGH);
}
The first line of code begins with an if. Within the following brackets, the condition to be tested is specified, in this case, if the button is pressed. If this condition is true (returns true), the code entered in the curly braces is executed.
As you may have noticed, the condition uses a comparison operator, namely a double equal sign (==). A common mistake is that only a single match is used. For the Arduino, however, a single equal sign is not "check if equal" but for "set left equal value right".
Using else
With else, you can add an additional action to your if statement, which is alternatively executed if the condition is not true. So if you add an else to the above code, the whole sketch would look like this:
#define LED_PIN 1
#define BUTTON_PIN 3
void setup() {
pinMode(LED_PIN, OUTPUT);
pinMode(BUTTON_PIN, INPUT);
}
void loop() {
if (digitalRead(BUTTON_PIN)==HIGH){
digitalWrite(LED_PIN, HIGH);
} else {
digitalWrite(LED_PIN, LOW);
}
}