Inside Blink

Now, let us look at the program itself, and figure out how it works.

The first line says: #include <Pinball.h>

This line is not necessary for most Arduino programs, but we will be using some special SPICE-camp language to program our Pinball machines. So we’ll start all of our programs with this line.

The thing to note is that there are these strange words with flower braces, and something written inside the braces. These braces are what we call functions. This program is using two functions: setup() and loop(). They are used like this:

void setup() { WRITE SOMETHING HERE } void loop() { WRITE SOMETHING ELSE HERE }

These two functions are always necessary for the Arduino to work. Everything written inside the setup() function is run by the Arduino only once (at the beginning). Everything written inside the loop() function is run continuously in a “loop”. For example, in the program, the line:

pinMode(12, OUTPUT);

is telling the Arduino to make pin 12 ready for putting out voltages. This needs to be done only once, which is why it is inside the setup() function. The rest of the lines need to run continuously again and again, which is why they are inside the loop() function.

Let us look closely at what is inside the loop() function.

digitalWrite(12, 1); delay(500); digitalWrite(12, 0); delay(500);

The line:

digitalWrite(12, 1);

is telling the Arduino to write a high (“1”) voltage on pin 12. Similarly, the line:

digitalWrite(12, 0);

is telling the Arduino to write a low (“0”) voltage on pin 12. The line:

delay(500);

is telling the Arduino to go to sleep for 500 milliseconds, which is half a second.

So the Arduino is right now setting pin 12 voltage to high, then sleeping for half a second, then setting the pin 12 voltage to low, then sleeping again for half a second, and then repeating.

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