C - Morse Code Machine

So far, we have only used outputs - things that the robot can change to 1 or 0.

Inputs work in a similar, but opposite way - they can send a 1 or 0 signal back to the robot!

Our program then needs to decide what to do, depending on whether the signal is 1 or 0.

The switch module is a great example of an input - when one of the switches is pressed, the pin it is connected to will change to 1.

Assemble your robot like the picture. The connections should be:

Buzzer - P0

Switch - P1

Green LED - P2

Red LED - P8

To use an input, we need to read it to see whether it is 1 or 0.

We can use the read_digital function for this - to use it we just need to write pinnumber.read_digital()

In our case, this is pin1!

read_digital will return 1 if the switch is pressed, and 0 if it isn't.

To use an input, the robot needs to know how to make a decision.

We can do this with an If statement!

An If statement has two parts:

Condition - this is a test, and it goes after the if, followed by a colon. It will usually test if something is equal to something else - here we are seeing if P1 is 1.

Conclusion - this is some indented code after the condition, that is only run if the condition is True.

To check if something is equal to something else in Python, we need to use two equals signs (==).

Make the program in the picture - it tests if the switch is pressed, and then turns on the red LED if it is.

Test it out - does it do what you expect?

You may have found the LED only turns on if you are holding the switch when the program starts.

This is because the switch is only checked once - then the program is done!

Put the if statement inside a while True: loop, and test it out again - this way, the switch is checked every time the loop is run.

The LED should now turn on when you press the switch!

Let's add some more code so the LED turns off when we let go of the switch!

Add another if statement into the loop, that checks if the switch is 0 and then turns off the red LED.

Your LED should now be controlled by the switch!

Often, we want to do one thing if something is 1, and something else if it is 0, like turn on/off the LED.

We can use two if statements, but there is a shorter way - using an else.

Replace your second if statement with an else, to make an if/else statement:

If the condition is true, the code inside the if statement is run

If the condition is false, the code inside the else statement is run.

Your LED should still be controlled by the switch, but the program is simpler!

You may have noticed we have actually made our own Morse Code machine already!

By holding down the switch for a long time you can send a dash, and a short press would send a dot.

For this challenge, add some more code so that:

When the switch is pressed, the green LED and buzzer are on

When the switch isn't pressed, only the red LED is on.

Time for a harder challenge!

Using the Morse Code video from the first step, can you send a secret message to your neighbour?

Get them to decode it and see what they come up with - no speaking allowed!

A super hard challenge now - can you write a program that sends Morse Code for your initials (or even your whole name) automatically, but only when you press the switch?

If you're feeling really clever, try and use some loops to reduce the length of your program if you need to send lots of dots or dashes in a row.