CCC - Self-Driving Cars

Creating your first program

Open the Python editor by visiting python.microbit.org/. Your screen will look something like this:

• In the middle is where you will add your own code.
• On the left-hand-side is the reference menu - you can see examples of some of the code here, as well as help understanding these examples.
• On the right-hand-side is the simulator - a pretend micro:bit you can use to test your code.
• On the bottom is the Send to Micro:bit button, which you will use to send code to your physical micro:bit.

Edit the code on the screen, then flash it to your micro:bit to see the changes.

Try:

• Editing the image that is shown (hint: check the reference menu, under Display, for a list of images)
• Changing the number in the brackets after sleep (hint: this tells the micro:bit how long to keep your image on the display)
• Making the micro:bit scroll your name instead of 'Hello'

Testing the cars

Download the project hex file, and open it in the Python editor.

This file includes a library, car.py, and the main file to write your own code in.

Send this code to the micro:bit, plug it into the car's edge connector, and test it out - how far does the car drive before stopping?

What features do you need to add to the code to make the car work properly?

Currently, the car is set to stop as soon as one of the sensors goes over the black line.

Making them smart

The next step is to program the car to turn off the black line so that it can keep following the road.

IN-PERSON DEMO HERE - INFO TO BE ADDED

The Python way of writing this is:

elif left_sensor > 100:
    car.left_turn(500)

Where the number inside the brackets is how long the car should turn for - you will need to test out your own car to find the best amount of time.

Below is the full code (replacing your current while loop), including turning left if the left sensors goes onto the line. Try it out, then add the right sensor yourself.

while True:
    left_sensor = pin2.read_analog()
    right_sensor = pin1.read_analog()
  
    if left_sensor <= 100 and right_sensor <= 100:
        car.forward(500)
    elif left_sensor > 100:
        car.left_turn(500)
      
    else:
        car.stop()

Test out your car on the roads - how well can it cope with the corners?

Improving your car

Your car might not be able to cope with very tight turns - test it out on some of the winding bits of road.

To improve this, you could:

• Tell your car to travel for less time before checking the sensors.
• Tell your car to slow down whilst turning.

You can add another argument to the turn functions, so they have two numbers:

car.left_turn(500, 750)

• 500 says turn for half a second
• 750 says turn at a speed of 750 - the slowest you can turn is 300, the fastest is 1023.

Try out different numbers to see if you can get your car safely round the difficult bends.

Can you design your own roads to test your car on?

Designing a smart road system

- this part is challenging, an extension for those who have been before

- using radio to listen out for stop signals, take a 'pedestrian crossing'

- add 'while message says go' and adjust the indents

- when this is working, further extension is to adjust the code on the crossing - how long should it stop the cars for before letting them drive again? how long after pressing the crossing should it wait before telling the cars to stop? how long after telling the cars to stop should it wait before letting the pedestrian know that it is safe to cross (consider the delay in stopping)?

ALL OF THIS SECTION AS A HANDOUT / PAGE WITH GIFS SHOWING THE INDENTS

Other extension possibilities: coding traffic light LEDs