Arrays are a data structure which allows multiple values to be grouped together in an easily accessible method. If you can remember back to chapter two, we talked about variables and how they can be thought of as containers sitting on a shelf. Well to extend that analogy. If a variable is a single container, then think of an array as a subdivided set of drawers on a shelf, you can still access that space on the shelf, but rather than being a single container, there are different miniature containers at that space. An array is structured like so let’s take a look so in the Arduino IDE, and there are four key elements to an array you have. The array. Data type in this example we’re using int, much the same as we with another variable. We have array1. That could be called anything could be called Sydney. Doesn’T have to have the word, Rainer it’s, just a unique name in the same way that a variable has a unique name. It has the array index just there, and then it has the array content which we have here inside of our curly bracket, and each element is separated by commas. There are four unique elements or pieces of data inside there, each of which isn’t it. Now you can create different types of arrays. However, an array can only hold a single type of data, so if you declare an array as an int, then it can only hold integers.
Like the example data now like variables, arrays can be declared first and defined later, which allows you to create an array with blank spots in it and add data to it later on in your program, the array name follows the same conventions as a standard variable. It must be unique, it is case sensitive and has a scope, global or local. The index refers to the position of the array context. When declaring an array, you can define the number of elements or places if you wish that you have in your array and finally, the array contents is the data that is inside your array. So let’s take a look at some examples of how you can declare and define arrays so adding on from the example here I’ve created for different types of arrays. We have array1, in which we said that we have four elements to the array and inside we have these four pieces of data 11, 5, 4 and 9. Now we have a raid 2 in which we’ve left the index blank, so we’re not explicitly telling it. How many elements are in our array, but you can see that that has 9 elements here. In fact, we can add a zero to that 0 index. It all in fact, with 10 to the under there. So the example a little better for 1 through to 10. So there are 10 elements in this array and once it goes through that the compiler will automatically sort out how many elements are in there and populate that yourself.
So you don’t always have to define number of elements in a write, a little bit more efficient. Now, here, we’ve created in a race 3 we’ve said that there are 10 elements in the array and we’ve left off the content. Now that is the same concept. If we’re declaring an integer just and a variable, we could go array a sum value and instead of being letting it equal something we’re, just declaring and defining it later on, where we just leave out the equal signs and the value, and instead just put that semicolon. There to terminate the one well in the same way, we’ve said: we’ve left out the equal signs and the curly brackets in the content, and it will populate an array with ten blank spaces in which we can go and fill in later on now, arrays don’t just Have to be in here, we’ve got a child class or a character where it uses the ASCII table and it creates character, type elements and the character is 8 bits or one byte of data. We said that there are six elements in the array we have h. E l, l o now you’ll notice, that’s only 5 we’ve left space because there is actually a terminating character in that array. There are six elements to it. Those arrays don’t just have to be in now to access an array you use its name and the index number of the element that you wish to access.
Something to keep in mind, though, is that as this many things in programming arrays as 0 index. This means that the first element in an array is indexed as number zero and the second element as index one and so on and so forth. Whilst it can definitely be a bit confusing at times, it makes a lot of sense once you start getting used to it. So let’s take a look at another example. Let’S say in void loop. I wish to access part of an array. Well, we think, as we said, standard variable, you don’t have to use the data pipe again. You simply use the array name so let’s take array 1. Then inside my square bracket here is where I use the index to reference a particular element in the array. So if I say array 1 0, that means I’m accessing that 0 index of the very first element in the array index number 0, which is 11 so array, one element 0, would equal 11. Likewise, if it is index 1, that is the second space in the array which is 5, 2 would be 4 and 3 would be 9, and you have 0 1 2 3, which is 4 elements in total. But if it’s confusing, as I said, but you do get used to it likewise, I can access. Even though put the word hello there in my array, I can actually access each individual letter so rather than taking a string for example and saying all right string.
Some word equal to load and I’ve only got access to the string as a whole. Without some extra string, manipulation and data control, I can simply say alright. I want to find out what the second letter is in this array, and I know that it’s an 8 or I could leave that blank and fill in another word later on and then break it apart in the same method, which is really really cool. So a really handy use in arrays that you’ll see later on is we can create a for loop, so we create a for loop standard counting loop into I and let’s say I wanted to use array 2. As for output, pins – and I want pins 1 through 2 – tend to be output, pins let’s say. While I is less than 10, I plus plus a standard incrementing for loop. I could then use pin mode array, and you might index, put the local variable hi and that’s really really cool anyway. We’Ll get to that in a second and we’ll. Take a look at a more holistic example to re. Explain how that works in just a moment. So now that you know a bit about arrays and how they work, let’s put them to good use in a practical example to make an LED sequencer using your knowledge of LEDs wire up, eight LEDs to your Arduino board, using whatever things you choose. However, I use pins 2 through to nine, so eight LEDs, all up and we’re, going to make them do some cool things.
So I’ve got my board here fairly simple. I put my LEDs with a resistor going to ground from them so I’m, using a high logic or active higher logic. I should say, and then I’m taking my ground to my Arduino board and the pin out directly to the LEDs when we apply five. Five volt signal to them: they’re going to turn on which is cool, so here’s, a sketch and it’s fairly straightforward we’ve got an array here called LED array and I’m going to use these for the pin out to reference which led I’m controlling. So the array contents are to sequentially through to nine, which corresponds to the pins I’m using pins two through to nine then delay time, which I’m just using as a counter for how rapidly we want the LED to sequence. Then, as I mentioned before, inside setup I’m, using this for loop I’m using pin modes with the array indexes of I and I’m declaring them all as outputs now, what this does let’s go through through the basics of this, because it’s, a really good example of using Arrays, so at first for this for loop, if you know from the previous chapter when we’re talking about logic statements, I would create a variable and we’ve initialized is 0, the first time this runs. I is equal to 0. So what a third is? King mode LED array 0, which corresponds to the first element in our array. So 2 now LED array is 0 is equal to 2, so it would put a 2 or actually a 2 in place of that, and then it would just define 2 as an output.
Likewise, when, when that’s finished, I will increment again to 1 now LED array. 1 is equal to second element there, which is three so order, replace all of that with a three and so on and so forth. Until that all is done, which is really cool, because, instead of writing, our pinmode output eight times, which is really clunky and bulky for lines which, like add two lines of code and two spaces for our curly brackets, gets the same thing done and it’s really handy. Because if we want to increase the size of a la zero, we can simply add some more elements to it: change the changes of bounding of our for loop, and then we can declare as many as we want just really cool. So that is our pin modes done now. We’Ve got two separate for loops here, really really simple. All we’re doing is we’re going to come LEDs on in order until they’re, all on so I’m, going to turn them off again in the same order and can play around with the exact animation really easily by altering the flow of our four loops. First of all appear again really expanded, counting we’re, saying that’s inside which is initialized to zero. While I is less than or equal to seven again, it could be in fact you know, but to make it easier you could say. While I is less than eight going to accomplish the same thing, increment I’ve spent accounting we’re going to write, LED array.
I so I referencing each pin and writing at. I writing I, which is going to be an order from element. 0. 1. 2. 3. 4. 5. 6 7, which is 8 elements. Alright remember: zero indexing, which corresponds to 2 3 4 5 6 7 8, which is the LED pins we’re, going to turn them all 1 and wait for delay time, which is equal to 150 milliseconds each time so there’s a time for them to step up an Increment then, when it’s done that we’re going to turn them back off and wipe back down in the same way using the exact same concept but we’re initializing, I 7 running a while. I is greater than or equal to 0 and B incrementing. I each time which is really cool, so let’s go ahead and load this up to our board, plug that guy, in short, got the right, comfort, selected and hit upward, and you can see it’s actually already running a headed program on there just a moment ago. You can see the LEDs turning on and off in order really really handy. Now again, you could implement a different, slightly different animation, we’ll just copy this place to full up here and then, instead of turning it on we’re going to turn it off. So what this will do is turn them all on and then all I can do a do. A linear work, which is really really cool, they’re, both still leaning out but up, goes in the same direction.
So you can see that it’s all turning on then they start wiping off really cool. I raise a really simple but really powerful tools and that they’re really good, especially for controlling outputs, where you might have a whole group of LEDs. Now eight LEDs doesn’t sound like much but let’s say you wanted to control a 64 or an 8×8 LED matrix. Well, you can use arrays and rather than having to declare each pin by itself and the pin mode and accessing each one by cross referencing, which pin number you’re going to you simply create it as an array and access each element that you want so Row.
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