Discussion: This lesson continues our quest of learning more about programming and electronics. In previous lessons, we already discussed several reasons why we have chosen to use an Arduino board as the tool to help us learn. Specifically, we chose the Arduino Uno board. The Uno is the baseline Arduino board, being the one around which other Arduino boards are designed . Therefore, the Uno is a great place for us to start digging in. It's also a fantastic launchpad if you decide to move on to other platforms in the future. In this lesson, we'll do a high-level overview of the Arduino Uno hardware. Specifically, we'll cover: The Concept of an Arduino Board The Three Types of Pin Header Rows: Digital, Analog, and Power Other Miscellaneous Valuable Tidbits The Concept of an Arduino Board As we discuss the hardware, I recommend holding your Arduino board in your hand. Pause the video as needed to take a closer look at the board as we discuss the different components. First, I want to point out that the integrated circuit is the brains behind the Arduino board. It's very likely that the circuit is the Atmel ATmega 328, which is an 8-bit microcontroller. Don't worry about that fancy name. The only thing I want you to understand is that everything on the Arduino board is meant to support that integrated circuit. So, the Arduino exists to make it easy to use this microcontroller. If you look closely at the microcontroller, it may look slightly different from mine, depending on which model you have. It might be really small, called a surface mount component, or it could be a big one like mine, which is called a DIP. Either way, there will be little metal prongs that stick out of the side. These are called pins. These pins are how the microcontroller is able to do stuff. These are used to interface with other hardware and circuitry, such as LEDs, sensors, or even your computer. Therefore, we need to know how to actually connect them to other things. That's where the pin headers come into play. Pin headers, sometimes referred to as just headers, are the plastic rows of holes that stick up from the Arduino board. They are all along the border. Inside of the holes are little metal clips. When you stick a wire down into the hole, that wire will stick and stay there. For example, you can stick the wire that comes out of an LED or a resistor into those holes. The wires are called leads, by the way. The wire makes an electrical contact in that hole. In other words, the wire sticks in the pin header. The metal clamp inside the header clamps onto the wire, and an electrical connection between that wire and a specific pin on the microcontroller is then created. Digital Pin Headers There are three categories of headers: digital, power, and analog. The first one we'll discuss is the digital category. Digital pin headers make up the longest row on the Arduino board. They are numbered from zero to 13. That means there are a total of 14 digital pins that we can use. To make this lesson as practical and easy as possible, for our purposes when I say digital, I mean something that is a discrete state. Let's use color as an analogy. Something that is digital can only be either black or white. Digital does not care about any point of gray in-between. Therefore, digital pins are used in one of two ways. They can be used as inputs to do things like read a voltage. Otherwise, they are used as outputs, such as applying a voltage. When they operate as an input, they can only read two different voltage states - high or low. The same is true when they act as outputs. They can only output two voltage states - five volts (high) or zero volts (low). Just as in anything else in life, there is an exception to this. You'll notice that some of these pins have a little squiggly mark next to them. There should be six of them, located at pins three, five, six, nine, 10, and 11. These specific pins allow you to use a technique called pulse width modulation, or PWM. PWM is a technique that we'll dive into later in the course. It enables us to use digital pins in such a way that they appear as though they are outputting a varying amount of voltage. Again, we'll get into PWM in much greater depth later. Right now I just want to point out those pins, and why they are special. I also want to point out two other pins. Notice that pins zero and one have a "TX" and "RX" next to them with little arrows. That stands for transmit and receive. The Arduino uses these two pins to communicate between the board and the computer. For example, maybe you need to upload your code. Maybe executing your sketch performs serial communication between the Arduino and the computer. Serial communication is another concept we'll be learning later in the course. It's only important that you understand these pins used to transmit and receive. Therefore, it's best to only use pins zero and one as a last resort if you've run out of available pins. The reason for this is that sometimes
