Repeat an SOS Message (using LED module)

Note: This "Repeating an SOS Message" activity is equivalent to the one using a breadboard rather than an LED module.

In the previous activity on "Sending an SOS Message," you may have noticed that to create the letter "S" we repeated the code for three dots in a row, and to create the letter "O" we repeated the code for three dashes in a row. In programming we often have situations where we need to do the same sequence of commands multiple times in a row, and so there is a special programming concept known as a "loop" to make it easier to do this. There are several types of loops, but the version we will use in this activity is called a "repeat loop," because it tells the computer how many times to repeat a certain sequence of commands. In RoboBlockly you will find the repeat loop block in the "Loops" section (click the "Loops" button just below the "Logic" button):

The code blocks to be repeated click inside the repeat loop block, and the input value specifies how many times to repeat the code. We have shown how it works in the code below by replacing the "S" code blocks with a repeat loop, and similarly for the "O" blocks.

It is also possible to put loops inside of loops. In our SOS example, this feature will be particularly useful if we want to repeat the SOS message more than once. In other words, once we have the code for a single SOS message written using three repeat loops (one for each letter), we can put the whole thing inside another repeat loop and specify the number of times to repeat the SOS message.