Page 56 - Programming the Photon Getting Started With the Internet of Things

When verifying the firmware the compiler will tell you that it has successfully
compiled your code and that everything was acceptable to the C language standard. At the
bottom of the compile if you click the little icon for information, it will also tell you how

much of the flash memory has been used.

The Photon has a total of 1MB internal flash memory, which is divided into three main
areas. Beginning at the top of the memory space is where the bootloader is saved and
locked. The second region is reserved for storing system flags, and the third region holds

the actual user firmware.

Let’s take a closer look at our setup and loop functions that will always be the starting

point of every firmware that we write. We can start by using the word void before setup
and loop followed by a pair of curly braces.

The line void setup () means that we are defining a function called setup within our

code. Some functions are already defined for us, such as digitalWrite and delay. Setup
and loop are two functions that we must define for ourselves in every program we write.

We are not calling setup or loop like we do with digitalWrite or delay, but we are

actually creating these functions so that the Photon itself can call them. This might sound
a little bit confusing, but the best way to think of it is that we are trying to shorten our
code. Using void with both setup and loop allows us to not return any values within the
function, unlike other functions, so we have to say that these are void.

After the word void comes the function’s name and parentheses containing any
arguments. In our case both setup and loop do not contain any arguments, but we still
have to include the parentheses. Because we are defining a function within our code and

not calling a function, we do not have to close it with a semicolon. Instead, we use the
curly braces, which is where our code sits between in the function—this is known as a
block of code. Just because we define the functions setup and loop that does not

necessarily mean we have to use those functions to hold any block of code—we simply
just need to define them in every firmware we write, although in reality this may not ever
happen.

Let’s go back to our example sketch in Chapter 2:

//D7 LED Flash Example
int LED = D7;

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

void loop() {
digitalWrite(LED, HIGH);