Tasking in Ada on a Raspberry Pi

Ada provides an extensive set of capabilities for creating programs with concurrent code modules (tasks), for real-time programming, similar to Java threads. Those tasks are executed concurrently with the rest of the program, so I thought the best way to test them on a Raspberry Pi is by blinking two LEDs at different time intervals ;)

Accessing the GPIO pins on a Raspberry Pi from an Ada program requires a library, I'm using Linux Simple I/O Library by  Philip Munts.

Assuming we have two LEDs (and corresponding resistors) on GPIO17 and 18, here's the source code for blinking them at different intervals, using tasks.

--
--  GPIO LED Test using libsimpleio
--  task version
--
WITH Ada.Text_IO; USE Ada.Text_IO;
WITH GPIO.libsimpleio;

PROCEDURE blinky_tasks IS

  LED_red : GPIO.Pin := GPIO.libsimpleio.Create(0, 17, GPIO.Output);
  LED_green : GPIO.Pin := GPIO.libsimpleio.Create(0, 18, GPIO.Output);
  Ch : Character;
  Available : Boolean;

  task First_task;
  task Second_task;

  task body First_task is
  begin
    LOOP
      LED_red.Put(True); delay 1.5; LED_red.Put(False); delay 1.5;
      exit when Available = True;
    END LOOP;
  end First_task;

  task body Second_task is
  begin
    LOOP
      LED_green.Put(True); delay 0.5; LED_green.Put(False); delay 0.5;
      exit when Available = True;
    END LOOP;
  end Second_task;

BEGIN
  Put_Line("GPIO LED Test using libsimpleio - task version");
  New_Line;
  Put_Line("press any key to exit...");

  LOOP
    Get_Immediate(Ch, Available);
    exit when Available = True;
  END LOOP;
  LED_red.Put(False);
  LED_green.Put(False);
END blinky_tasks;

Note: Ada logo source Ada Belgium