B - Save our Robot!

Having red/green LEDs is a great start to communicating with our robot

What if we want to communicate more than just red or green?

Morse Code allows us to send any letter or number we like, just using a single light or buzzer!

Watch the video to find out more.

It's your turn to try and decode some morse code into words!

See if you can work out the sequence of letters in the video using the decoding card.

Make sure you get this challenge checked off when you know the answer!

Let's write a program that will send the letter S.

In the picture is a program to send 1 dot with the red LED. For your delay() lines, we suggest:

100 milliseconds for a dot

1000 milliseconds for a dash

Extend the program in the picture to send 3 dots, which is an S - your LED module should still be plugged in to a1 like the last lesson!

Good programs always try not to repeat code that does the same thing, so the program is as small and efficient as possible.

We could put the code for one dot in the loop, but this would just do dots forever - not what we want!

We are going to use a for loop to repeat something a set number of times.

A for loop takes 4 inputs:

Initialiser - this is used to count how many times the loop runs, and is usually called i

Condition - the loop runs until this is false. For example, this for loop would run so long as i is less than 3.

Incrementor - this is how much i is changed by, every time the loop runs. In this case, for every run of the loop, i is increased by 1 (++ just means add 1)

So this for loop starts with i=0. After the first loop run, i is increased to 1. After the second it is increased to 2, and after the third run it is increased to 3. When i=3, i is not <3, so the loop stops after 3 runs.

Put your code to send a dot with the red LED inside the for loop, so your robot sends an 's' with much less code.

Try changing the loop inputs, and see how it affects how many dots get sent!

Indentation is very important in programming - it makes it easy for others to read your code, and for you to read it later!

You can indent a line by pressing the TAB key.

Generally, if a line of code is inside something else, it should be indented more. For example, invent.begin(); is inside the setup, so it is indented 1 level

Our digitalWrite lines are inside both the setup, and the for loop, so they are indented 2 levels.

Try and make sure all your programs are indented properly! Ask your tutor if you are unsure.

You might have noticed when you were listening to the code, that between the letters we need longer gaps so you can tell when they start and finish.

A time of 2 seconds works well.

Put your for loop that flashes an S inside the main program loop, so it flashes S forever, and add a wait block so there is a gap of seconds between each S.

Make sure it is indented properly!

Let's make a program to get our robot to flash SOS using an LED, in case it has a problem.

Your program should flash the sequence of dots and dashes required for the letters SOS - for bonus points put it in the loop to make it flash SOS forever!

Try to shorten your program using for loops - you will need 3 separate loops, or 2 if you're really clever!

Using lights for Morse Code is great for long distances, such as between two ships, but what if you are looking the other way when your robot is in trouble?

Replace your LED module with the buzzer module like in the picture, so your robot buzzes SOS instead.

If you're feeling really clever, put the LED module back into another output and add some more code so it flashes and buzzes the sequence for S.O.S!