I'm Alive!

Having to write out specific values every time you need them is starting to become a problem. In the previous example, you had to write 24 three times and 10000 twice. Unless those values stay the same forever (which they might not, especially for the "10000", a value you may want to adjust), you'll have to update them everywhere they are used. Not only that, but you'll always have to remember what they mean, which is next to impossible if your code is more than a few lines long.

Luckily, there's a way around this problem.

Introducing CON blocks

PUB isn't the only kind of block available. CON blocks allow you to set constant values, that don't change, allowing you to call them by name.

Setting a constant is easy. Constant names can contain letters, numbers, and underscores (_), but must start with a letter or underscore.

Let's set constants for the LED pin and the count of times repeat will run before continuing. You can set as many as you want, but they must be inside a CON block.

CON
    LED_PIN = 24
    COUNT   = 1000

There can also be as many CON blocks as you like too.

CON
    LED_PIN = 24
CON
    COUNT   = 1000

It works exactly the same, but now if we need to change the values, we only need to change them in one place.

CON
    LED_PIN = 24
    COUNT   = 1000

PUB Main
    dira[LED_PIN]~~

    repeat
        outa[LED_PIN]~
        repeat COUNT

        outa[LED_PIN]~~
        repeat COUNT

Tip

Style is important

You may have noticed that all the constants are in capital letters when Spin is case-insensitive.

Why? It makes it easier to remember that it's a constant value.

Introducing OBJ blocks

Sometimes it's helpful to put code into a separate file. That way, if you have a nice piece of code that does something useful, you don't have to keep rewriting it for every project you work on. Instead, you can use it from where it is. Spin allows us to do this using the OBJ block. OBJ is short for object, because code files are called "objects" in Spin lingo.

To include an object in your code, you will need to provide the name of the file in quotes, and a short name under which you'd like to use the object. In our case, we'd like to add the file LamePinout.spin which contains pin assignments for the LameStation board. You can include the .spin extension or not, but the include file must be a Spin file.

OBJ
    pin : "LamePinout"

Now that you have the object included, you will be able to use the functions and constants inside of it.

To call a function in another object, prefix the short name of the included object, separating it with a period (.).

PUB Main
    pin.Null

To get the value of a constant in another object, add the short name and the hash symbol (#). Here's us grabbing the pin assignment for the LED from LamePinout.spin.

CON
    VALUE = pin#LED

So now let's set LED_PIN to pin#LED instead of having to remember what the pin is ourselves.

ImAlive.spin

OBJ
    pin : "LamePinout"

CON
    LED_PIN = pin#LED
    COUNT   = 10000

PUB Main
    dira[LED_PIN]~~
    repeat
        outa[LED_PIN]~
        repeat COUNT

        outa[LED_PIN]~~

        repeat COUNT

Tip

Fun Fact

This happens to be the example that comes pre-loaded on every LameStation unit!