PE1-4.1 Embedded Development Boards & the Arduino UNO

What this is and why it exists

Everything else in this area is analysis. This topic is a board on a desk with your code running on it, which is a different kind of knowing.

A development board exists to shorten the distance between an idea and a working circuit. Someone has already chosen the regulator, the crystal, the reset circuit and the connector. You spend your time on the part that is yours.

The vocabulary

• Development board — a microcontroller with its supporting parts already assembled and connected.
• Digital pin — a pin that reads or drives one of two levels.
• Analog input pin — a pin whose voltage is measured by a converter and reported as a number.
• PWM pin — a digital output that can switch rapidly, so its average is adjustable.
• Bootloader — a small program already on the chip that receives new code over the serial connection.
• Sketch — the name the Arduino environment uses for a program.
• IDE — the integrated development environment used to write and upload the code.
• Clone — a compatible board made by someone other than the original designer.

The mental model

Ask why a board rather than a bare chip. A bare microcontroller needs a regulated supply, a clock, a reset arrangement and some way of getting code into it. Building all of that yourself is a week of work that teaches you very little the first time. The board supplies it, and you get to the interesting part on the first afternoon.

The pin map is the thing to learn early, and it prevents more faults than any amount of theory. Not every pin can do every job. Some pins are digital only. Some can be read as analog inputs. Some can switch quickly enough to produce a usable average voltage, and some cannot. A wire in the wrong hole is a more common beginner fault than a mistake in the code. From the outside it looks exactly like a code fault.

Power has more options than expected and one dangerous mistake. The board can be powered over its data connection, from a separate supply, or through its input pin. What it cannot do is supply a large current to something you have attached. The regulator and the connector are sized for the board, not for your motor. Drawing too much through them is the standard way to destroy one.

Digital and analog ports differ in kind, not only in name. A digital pin has two states and nothing between them. An analog input is a converter, and its resolution and reference voltage together decide what you can actually measure. A converter with a five volt reference and a ten bit result resolves about five millivolts, and no amount of code changes that.

Clones matter practically. They are cheap and common, and they are usually compatible. They often use a different chip for the connection to your computer, so they need a different driver. Knowing that in advance turns a lost evening into a two-minute download.

The upload loop is the one you will run hundreds of times. Write the code, compile it, and send it to the board over the connection. The bootloader on the chip is waiting briefly after each reset, receives the new program, stores it and then runs it. Most upload failures are explained by that sentence. The wrong port is selected, the board does not reset, or another program holds the connection so the bootloader never hears you.

What you should now be able to explain or do

Say what a development board provides and why it is worth using. Read the pin map and tell which pins can do which jobs. List the ways to power a board and the failure that destroys one. Explain what the analog input's resolution and reference decide. Describe what the bootloader does, and use that to explain the common upload failures.

Check yourself