Add Microbit accelerometer demo.

This only works for the V1.3B Microbit (assumes accelerometer is MMA8653).

  * test-microbit/Makefile: add accelerometer.
  * test-microbit/README.md: likewise.
  * test-microbit/tests.gpr: likewise.
  * test-microbit/accelerometer.adb: new.

test-microbit/Makefile

@@ -16,9 +16,9 @@
 #  along with this program; see the file COPYING3.  If not, see
 #  <http://www.gnu.org/licenses/>.
 
-all: circle.hex events.hex seconds.hex
+all: circle.hex events.hex seconds.hex accelerometer.hex
 
-circle events seconds: rebuild.stamp
+circle events seconds accelerometer: rebuild.stamp
 rebuild.stamp: force
 	gprbuild -p -P tests
 	touch $@

test-microbit/README.md

@@ -1,13 +1,15 @@
 # micro:bit tests and demos #
 
-There are three programs built by `make` (or `gprbuild`, but `make` goes on to build hex files that can be dropped onto the micro:bit):
+There are four programs built by `make` (or `gprbuild`, but `make` goes on to build hex files that can be dropped onto the micro:bit):
 
 * `circle` displays a circle running round the LEDs: pressing button A alters the speed, button B alters the direction (clockwise/anticlockwise). The buttons are interrupt-driven.
 
 * `events` demonstrates `Timing_Events`. The top-left LED (row 1, column 1) flashes every 2 seconds, the LED in row 4, column 5 flashes every 5 seconds. _Why not the bottom right LED? because of the complicated mapping of GPIOs to LEDS_.
 
 * `seconds` checks out `Clock` functionality by flashing the centre LED once a second. You get to time a number of flashes with a stopwatch to make sure it really is once a second.
 
+* `accelerometer` displays a single LED: if the card is level, in the centre; as the card is tilted, the lit LED moves to the lowest edge.
+
 The tests interact with the micro:bit hardware using the [Ada\_Drivers\_Library](https://github.com/AdaCore/Ada_Drivers_Library). Configure it using that library's `project_wizard.py`:
 ```
 Welcome to the Ada Drivers Library (ADL) project wizard. This script will

test-microbit/accelerometer.adb

@@ -0,0 +1,48 @@
+with MMA8653;
+with MicroBit.I2C;
+with LEDs;
+with Ada.Real_Time;
+
+procedure Accelerometer is
+   Acc : MMA8653.MMA8653_Accelerometer (Port => MicroBit.I2C.Controller);
+begin
+   if not MicroBit.I2C.Initialized then
+      MicroBit.I2C.Initialize (S => MicroBit.I2C.S400kbps);
+   end if;
+
+   if not Acc.Check_Device_Id then
+      for R in LEDs.Coord'Range loop
+         for C in LEDs.Coord'Range loop
+            LEDs.Set_One_LED (R, C);
+         end loop;
+      end loop;
+      delay until Ada.Real_Time.Time_Last;
+   end if;
+
+   Acc.Configure (MMA8653.Two_G,
+                  MMA8653.High_Resolution,
+                  MMA8653.High_Resolution);
+
+   loop
+      declare
+         Detection_Limit : constant := 75;
+         Data : constant MMA8653.All_Axes_Data := Acc.Read_Data;
+         use type MMA8653.Axis_Data;
+         use type Ada.Real_Time.Time;
+      begin
+         LEDs.Clear_All_LEDs;
+         if Data.X > Detection_Limit then
+            LEDs.Set_One_LED (3, 1);
+         elsif Data.X < -Detection_Limit then
+            LEDs.Set_One_LED (3, 5);
+         elsif Data.Y > Detection_Limit then
+            LEDs.Set_One_LED (1, 3);
+         elsif Data.Y < -Detection_Limit then
+            LEDs.Set_One_LED (5, 3);
+         else
+            LEDs.Set_One_LED (3, 3);
+         end if;
+         delay until Ada.Real_Time.Clock + Ada.Real_Time.Milliseconds (100);
+      end;
+   end loop;
+end Accelerometer;

test-microbit/tests.gpr

@@ -1,4 +1,4 @@
---  Copyright (C) 2018, 2020 Free Software Foundation, Inc.
+--  Copyright (C) 2018-2023 Free Software Foundation, Inc.
 --
 --  This file is part of the Cortex GNAT RTS package.
 --
@@ -20,7 +20,10 @@ with "Ada_Drivers_Library/ada_drivers_library";
 
 project Tests is
 
-   for Main use ("circle.adb", "events.adb", "seconds.adb");
+   for Main use ("circle.adb",
+                 "events.adb",
+                 "seconds.adb",
+                 "accelerometer.adb");
    for Languages use ("Ada");
    for Source_Dirs use (".", "../test-common");
    for Object_Dir use ".build";