programming-buttons.md

Programming the Buttons

Setup

First update the import at the top of your file to include Button.

from gpiozero import Button, LED

Near the top of your file, after you setup the LEDs and before the colour constants, setup your buttons with the pin numbers that you connected them to when building your circuit.

red_button = Button(-1) # Change the pin number to match your circuit
blue_button = # Setup based on your circuit
yellow_button = # Setup based on your circuit
green_button = # Setup based on your circuit

Running Code when the Buttons are Pressed

In order to run code when the buttons are pressed, copy the incomplete button_pressed and button_released functions below the play_pattern function.

def button_pressed(button):
    # Code to respond to buttons being pressed goes here

def button_released(button):
    # Code to respond to buttons being released goes here

Both of these functions require a single argument named button and will not return anything. To run these functions whenever the buttons are pressed and released, configure the GPIO library to call them. Below the button_pressed and button_released functions, add the following code for each button. For example, to configure the red button, use the following code.

red_button.when_pressed = button_pressed
red_button.when_released = button_released

It is important to reference the functions, but not call them when configuring the GPIO library. You refer to the function by using it's name alone, without any parentheses or arguments. If you call the function, the GPIO library will be configured to run the return value of the function when the button is pressed or released. This might cause an error when this line of your program runs, or your program may work without any errors, but it will not behave how you expect it to.

When correctly configured, the GPIO library will call the button_pressed and button_released functions with the button that was pressed as the argument whenever a button is pressed or released, respectively. For example, if the red button was pressed, button_pressed would run, and the value of it's argument would be equal to red_button.

Responding to Button Presses

Identifying the Button for each Colour

In order to identify what colour a button corresponds to, copy the incomplete get_colour_for_button below the get_led_for_colour function.

def get_colour_for_button(button):
    # Code to return the colour for each button goes here

The get_colour_for_button requires a single argument named button. This function will take a button as an argument and return the integer colour value that the button corresponds to.

Implement the get_colour_for_button function. Remember that you defined the colour values when writing the pattern code.

Lighting the LEDs

To respond to button presses, you must implement the incomplete button_pressed and button_released functions you created earlier.

When a button is pressed, the button_pressed function should

1. Light up the LED corresponding to the button that was pressed
2. Check if the button that was pressed matches the pattern

When a button is released, the button_released function should

1. Turn off the LED corresponding to the button that was released

Make button_pressed and button_released turn the corresponding LED on and off as described above. Don't worry about checking if the button matches the pattern yet; this is included in a later step.

Testing

Before going further, make sure that your button code is working. Add the following code to the end of your file.

while True:
    sleep(0.1)

Run your program and make sure that the corresponding LED lights up whenever you press the button, and goes out when you release it. Make sure to test all four buttons. If the buttons don't do what you expect them to, there may be a problem in your circuit or code. Identify and fix any problems, then run your program again to check if the problem has been fixed.

Delete this test code once you know the buttons are working correctly.