AdaCore Blog

Ada for micro:bit Part 2: Push buttons

by Fabien Chouteau

Welcome to the Ada for micro:bit series where we look at simple examples to learn how to program the BBC micro:bit with Ada.

If you haven't already, please follow the instructions in Part 1 to setup your development environment.

In this second part we will see how to use the two buttons of the micro:bit.

Interface

To know if a button is pressed or not, we will use the function State of the MicroBit.Buttons package.

  type Button_State is (Pressed, Released);

type Button_Id is (Button_A, Button_B);

function State (Button : Button_Id) return Button_State;

Arguments:

  • Button : The Id of the button that we want to check. There are two Ids: Button_A or Button_B.

Return value:

  • The function State return the Button_State that can be either Pressed or Released.

We will use this function to display the letter A if the button A is pressed, or the letter B if the button is pressed.

Here is the full code of the example:

  with MicroBit.Display;
with MicroBit.Buttons; use MicroBit.Buttons;
with MicroBit.Time;

procedure Main is
begin

   loop
      MicroBit.Display.Clear;

      if MicroBit.Buttons.State (Button_A) = Pressed then
         --  If button A is pressed

         --  Display the letter A
         MicroBit.Display.Display ('A');

      elsif MicroBit.Buttons.State (Button_B) = Pressed then
         --  If button B is pressed

         --  Display the letter B
         MicroBit.Display.Display ('B');
      end if;

      MicroBit.Time.Delay_Ms (200);
   end loop;
end Main;

Following the instructions of Part 1 you can open this example (Ada_Drivers_Library-master\examples\MicroBit\buttons.gpr), compile and program it on your micro:bit.

See you next week for another Ada project on the micro:bit.

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About Fabien Chouteau

Fabien Chouteau

Fabien joined AdaCore in 2010 after his engineering degree at the EPITA (Paris). He is involved in real-time, embedded and hardware simulation technology. Maker/DIYer in his spare time, his projects include electronics, music and woodworking.