Pushbuttons

To the left and right side of the LED display, the micro:bit module has two tactile pushbuttons labeled A and B. The micro:bit module can be programmed to respond to these buttons being pressed. Each button exists as an object referred to as button_a and button_b.

For example, if you want to know how many times button A gets pressed since the micro:bit module has turned on (or since the last time you asked how many times button A was pressed, whichever is most recent), you can use button_a.get_presses. Similarly the same can be done for button B.

Example: get_presses.py

Note sleep(5000) at the beginning of the next example program.  When you flash the program, use these 5 seconds to press button A as many times as possible.

After 5 seconds, the program then stores the number of times button A got pressed since startup into the variable called numberOfPresses. The last line of the program uses the display to scroll the numberOfPresses.

  • Enter, save, and flash get_presses.py to your micro:bit
  • Immediately Press button A as many times as possible in 5 seconds.
  • Watch the display to see how many times you pressed the button.
#get_presses.py

from microbit import *

sleep(5000)

numberOfPresses = button_a.get_presses()
display.scroll(numberOfPresses)


Try This

  • Using the previous example as a model, write a program that displays the number of times button B gets pressed after 10 seconds pass from startup.
  • Write a program that displays the number of times both button A and button B get pressed after 10 seconds from startup.

Example: is_pressed.py

You can write a statement for each buttontell if it is pressed. The button_a.is_pressed method will return either True or False depending on whether or not button A is currently pressed. These methods often work well with conditionals. For example, the following program displays a check mark if button A is pressed. Otherwise, it will display an X.  

  • Enter, save, and flash is_pressed.py to your micro:bit.
  • Press button A to see the display change.
#is_pressed.py

from microbit import *

while True:
    if button_a.is_pressed():
        display.show(Image.YES)
    else:
        display.show(Image.NO)

Not pressed:    Pressed:


Try This

  • Use the display to show the letter A when the A button is pressed.
  • Use the display to show the letter B when the B button is pressed.

Example: was_pressed.py

Another commonly used method of the buttons is to be able to tell if the button was pressed since the micro:bit module turned on, or since the last time the code checked to see if it was pressed,  whichever is most recent. The button_a.was_pressed method returns True or False depending on whether or not button A was pressed.

For example, was_pressed.py will display a check mark if button A was pressed in each 5 second interval. If was not pressed in a five second interval, then it will display an X.

  • Enter, save, and flash was_pressed.py to your micro:bit.
#was_pressed.py

from microbit import *

while True:
    sleep(5000)
    if button_a.was_pressed():
        display.show(Image.YES)
    else:
        display.show(Image.NO)

Your Turn

  • Write a script to check if button A was pressed every 10 seconds instead of every 5.
  • Write a script to check if button B was pressed every 10 seconds instead of button A.