Scratch 4 Arduino is a custom version of scratch that makes it super easy to get up and running with Arduino programming. This worksheet is going to show you how to get set up and start making your first programs using S4A.

For a great little introduction to S4A, check out the first 10 pages or so of this presentation.

When you first launch the program, if you don’t have your Arduino connected your stage (the bit at the top right of your screen) will look like this :

When you connect the Arduino, the “Searching…” message should disappear and the numbers on the analog pins should start jumping around

Up in the top left of your screen are all the different categories of Scratch blocks for making your program. If you’ve used the original version of scratch before, this should be very familiar, apart from the additional section that comes with s4a, a blue one titled “Motion”:

If you go to the blue “Motion” section, you should see all of S4A’s special Arduino blocks. We will look at all of these over the coming weeks, but to start off with, we are going to concentrate on using these two :

These let us turn pins 10-13 on or off. It just so happens that the Arduino has an LED light already attached to pin 13. Try dragging these blocks into your workspace, clicking on them to turn the LED on and off and see if you can spot where it is on the board.

Controlling the onboard LED

There are a whole bunch of different ways we can control stuff in Scratch. Let’s look at a few interesting ways of turning our light on and off.

Looping

This script will blink your LED on and off every second (with S4A the fastest this can be is every 0.7 seconds)

Mouse Control

This script turns the LED on whenever your mouse button is pressed

Keyboard Control

These scripts turn the LED on when you press the left arrow key, and off when you press the right arrow key.

So Scratch’s onboard LED is OK, but it’s not the brightest LED in the world, and we have no way of putting it where we want, or changing it’s colour. Knowing how to use external LEDs is a super useful thing (especially with robots - colourful blinky light sare a must have!) This circuit shows you how to attach an external LED to pin 13. Just make sure that the longer leg goes into pin 13.

Because this is on the same pin as the onboard LED, we don’t have to change any of our scripts for this to work :)