Bench Ready

Right now the Arduino board is a strange object. By the end of this band it will be a tool you know how to use. That is the whole job.

You will not build a circuit yet. You will not use the breadboard. You will use one small light that is already built into the board, so that if something goes wrong, you know the problem is the computer or the code. It cannot be the wiring, because there is no wiring.

What you need in front of you

• Your Arduino Uno board
• The USB cable that came with it
• A laptop or computer
• Your kit box, unopened is fine for now
• A pen and something to write on

By the end you will be able to

• Point at any part of the board and say what it does
• Send a program from your computer to the board
• Read a program and say what each line does
• Change a program and send it again
• Read an error message and find the line it is talking about

An Arduino is a very small computer on one flat board.

It is not like a laptop. It has no screen. It has no keyboard. It cannot browse the internet. It does one job: it follows a list of instructions that you give it, and it does that over and over until you unplug it.

What makes it useful is that it can control electricity. It can switch a light on. It can turn a small motor. It can read a sensor and find out how bright a room is, or how warm, or how far away something is. Then it can decide what to do about that.

The list of instructions you give it is called a program. In the Arduino world we call one program a sketch. Both words mean the same thing here.

Look at your board

Take the board out and hold it. Compare it to the picture below. Find each labelled part on the real board before you read on.

What each part does

You need one piece of software: the Arduino IDE. It is free. It is the program you write in, and it is the program that sends your sketch to the board.

IDE is just a name. You do not need to know what the letters stand for.

Now plug in the board

Before you touch any code, do this small activity. It takes ten minutes and it will make the next part much easier to understand.

Write three instructions on a piece of paper, in big letters:

If you have someone with you

If you are on your own

Hold on to what happened in question 2. Stopping, taking the new instructions, and starting again from the top is exactly what the board does every time you press Upload. It cannot change its instructions while it is running them.

Here is your first sketch. Do not upload it yet. Read it first.

It will look strange. That is normal and expected. You are not supposed to understand all of it yet. Read it anyway, guess what it does, and write your guess down. Then we will go through it properly.

void setup() {
  pinMode(13, OUTPUT);
}

void loop() {
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}

Do not skip this. Guessing and then finding out you were wrong is the fastest way to learn this material. Nobody is marking your guesses. Question 4 catches nearly everybody, including people who have been doing this for years, so guess anyway.

Now we go through it slowly. Every symbol. Nothing skipped.

The two groups

Look at the sketch again. It has two blocks. Each one starts with a name and a pair of curly brackets.

void setup() {
  ...
}

void loop() {
  ...
}

These are two groups of instructions. The board treats them very differently:

• setup runs one time, right at the start, when the board is switched on or has just received a new program.
• loop runs again and again forever, from its first line to its last line, then back to its first line, until the board loses power.

This is the same thing that happened in the paper activity. Stand up once. Then say your name and sit down, over and over.

Every Arduino sketch must have both of these groups. Even if one of them is empty.

The symbols

The instructions, one at a time

pinMode(13, OUTPUT);

This says: pin 13 is going to be used for sending electricity out.

Break it into pieces:

• pinMode is the name of the instruction. It means "set up how a pin will be used".
• Inside the round brackets are two details, separated by a comma.
• 13 is which pin you are talking about.
• OUTPUT means this pin will send electricity out to something, rather than read something coming in.
• ; ends the instruction.

It is in setup because you only need to say this once. The pin does not forget.

digitalWrite(13, HIGH);

This says: switch pin 13 on.

• digitalWrite means "switch a pin on or off".
• 13 is the pin.
• HIGH means on. The pin now puts out 5 volts.

The opposite is digitalWrite(13, LOW); which means switch pin 13 off. The pin drops to 0 volts.

There is no in-between. With digitalWrite, a pin is fully on or fully off. Getting in-between brightness is what Band 2 is for.

delay(1000);

This says: wait here and do nothing.

The number is in milliseconds. A millisecond is one thousandth of a second. So:

• delay(1000); waits one second
• delay(500); waits half a second
• delay(2000); waits two seconds
• delay(100); waits one tenth of a second

To turn seconds into the number you need, multiply by 1000.

Two rules about typing

Where does the program actually live?

Many people think the program is running on their laptop and being sent to the board bit by bit. It is not. Prove it to yourself.

Read the worked example

Now open b0_02_signature_worked.ino and upload it. Watch it first, then read it.

This one blinks a signature: two short flashes, one long flash, then a rest. It is the kind of thing you will make yourself at the end of this band.

int ledPin = 13;
int shortFlash = 150;
int longFlash = 700;
int gap = 200;
int rest = 1200;

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

void loop() {
  digitalWrite(ledPin, HIGH);
  delay(shortFlash);
  digitalWrite(ledPin, LOW);
  delay(gap);

  digitalWrite(ledPin, HIGH);
  delay(shortFlash);
  digitalWrite(ledPin, LOW);
  delay(gap);

  digitalWrite(ledPin, HIGH);
  delay(longFlash);
  digitalWrite(ledPin, LOW);
  delay(rest);
}

There is something new here. The five lines at the top give names to numbers.

int shortFlash = 150; means: make a name called shortFlash and put the number 150 in it. After that line, anywhere you write shortFlash, the board reads it as 150.

Look at how the rest of the sketch uses those names instead of numbers. delay(shortFlash) instead of delay(150).

Why bother? Two reasons. First, delay(shortFlash) tells you why that delay is there, and delay(150) does not. Second, if you want to change the short flash, you change one line at the top instead of hunting through the sketch for every 150.

You do not have to use this yet. Band 1 makes you feel the difference by measuring it, which works far better than being told.

Three short activities. They look small. They are the part that makes the difference between copying and understanding.

a. Follow the code by hand

Go back to b0_01. Number the four lines inside loop() as L1, L2, L3, L4.

Copy this table onto paper and fill in the empty boxes. The first row is done for you.

b. Meet an error message

Open b0_03_buggy_semicolon.ino and press Verify. It will fail. That is what it is for.

Here are lines 22, 23 and 24 of that file:

void setup() {
  pinMode(13, OUTPUT)
}

The semicolon at the end of line 23 is missing. Now look at the red message at the bottom of the IDE. It says something close to this:

b0_03_buggy_semicolon.ino:24:1: error: expected ';' before '}' token

Read that message piece by piece:

• b0_03_buggy_semicolon.ino is the file.
• 24 is the line number it is complaining about.
• expected ';' means it wanted a semicolon.
• before '}' token means it noticed when it reached the curly bracket.

c. A thinking question

In b0_01, imagine you swapped the two digitalWrite lines around, so that the LOW one came first and the HIGH one came second. Everything else stays the same.

Would someone watching the board see any difference? Write one sentence and say why.

Now you change someone else's code before you write your own. This is deliberate. It is much easier than starting from an empty screen, and you learn just as much.

Work on a copy of b0_01. Use File then Save As to make a copy first, so you still have the original. Do all three tasks in order.

Bronze

Make the light blink twice as fast. Write down which numbers you changed and what you changed them to.

Silver

Make the time it is on different from the time it is off, so it looks like a heartbeat rather than a steady tick.

Gold

Make it flash three times quickly, then pause for two seconds, then repeat forever. Count how many lines your answer needed. Then work out how many lines it would take to flash ten times, and write that number down too.

Keep the two numbers from Gold somewhere safe. At Band 2 you will learn a way of doing this same job where going from three flashes to ten costs you one character. Comparing the two ways is how you will understand why that tool exists.

How to go about it

Designing away from the keyboard is a habit worth building now, while the hardest thing you can get wrong is one light.

Also due this band: your kit list

Open your kit box. Go through it part by part. Write a list with the name of each part and how many of them you have.

If you do not know what something is, look at the paper that came with the kit, or search the web for "Arduino starter kit parts" and match the pictures. If anything is missing or broken, deal with it now rather than at Band 4, when you are halfway through a build and cannot finish.

Most missing parts have a substitute you already have, so check this list before you go looking for a shop:

• Resistors: anything from 200 to 470 ohms works in place of a 220. The light is a little dimmer at the high end. Nothing is harmed.
• LEDs: any colour works anywhere. The colours in this course are only so the instructions can name them.
• Jumper wires: you can get by with fewer than the count given, by taking a wire out of a finished part of a build and reusing it, as long as you write down what you moved.
• The buzzer, the light sensor, the potentiometer: these have no substitute. If one is missing you can still finish every other part of the band it belongs to. Skip that one part and come back.

If somebody is running this course for you, tell them now. If you are on your own, note it in your build log so you remember why a later part had to be skipped.

Show your work

Post a ten second video of your signature blinking, plus your build log for this band. Then look at two other people's signatures and check yours is different from both. If it is not, change yours.

This is code you have not seen before. Do not upload it. Answer from reading only. Write your answers down, then check them.

void setup() {
  pinMode(12, OUTPUT);
  digitalWrite(12, HIGH);
}

void loop() {
  delay(2000);
  digitalWrite(12, LOW);
}

1. What does the light do during the first two seconds?
2. What does it do after that?
3. How many times does digitalWrite(12, HIGH) happen in the first minute?
4. Someone says: "the light stopped changing, so loop must have stopped running." Are they right? Explain.
5. Add one line to make the light blink instead. Where does it go, and what is it?
6. Which single line would you delete to make the light never come on at all?

Work down this list in order. Do not skip. Most first-week problems are on it.

Look back at where you started. You now know what the board is and what each part of it does. You can send a program to it. You can read a program and say what each line does. You can change one and send it again. You have met your first error message and you know the trick for reading it.

That is a real skill and you built it in one band.

Before you move on, make sure you have

• Your working signature, and a video of it
• Your kit list, with every part named and counted
• Your build log for this band
• Your two numbers from the Gold task
• Your one sentence about why the board kept blinking on the phone charger
• Five or six correct answers in Part 10, including question 4

Next is Band 1: Signal Tower. You will open the breadboard, build a real circuit with three lights, and make something a stranger can understand without you standing next to it.