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Case Study 3: Embedded Systems

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Introduction

In this case study, we will explore the development of an embedded system using Ada. Embedded systems are specialized computing systems that perform dedicated functions within larger mechanical or electrical systems. They are often constrained by real-time performance requirements, limited resources, and the need for high reliability.

Objectives

  • Understand the unique challenges of embedded systems.
  • Learn how to use Ada for developing embedded applications.
  • Implement a simple embedded system project.

Key Concepts

Embedded Systems Characteristics

  • Real-Time Constraints: Must meet strict timing requirements.
  • Resource Constraints: Limited memory, processing power, and energy.
  • Reliability and Safety: High dependability and fault tolerance.
  • Hardware Interaction: Direct interaction with hardware components.

Ada Features for Embedded Systems

  • Strong Typing: Helps prevent errors.
  • Concurrency Support: Tasks and protected objects for real-time operations.
  • Low-Level Programming: Access to hardware and memory.
  • Safety and Reliability: Built-in checks and exception handling.

Practical Example: Temperature Monitoring System

System Description

We will develop a simple temperature monitoring system that reads temperature data from a sensor, processes the data, and triggers an alert if the temperature exceeds a predefined threshold.

Components

  • Temperature Sensor: Simulated using a function.
  • Processing Unit: Reads and processes sensor data.
  • Alert System: Triggers an alert if the temperature is too high.

Step-by-Step Implementation

1. Setting Up the Environment

Ensure you have an Ada development environment set up. Refer to Module 1 for detailed instructions.

2. Defining the Sensor Interface

Create a package for the temperature sensor.

-- sensor.ads
package Sensor is
   function Read_Temperature return Float;
end Sensor;
-- sensor.adb
package body Sensor is
   function Read_Temperature return Float is
   begin
      -- Simulate reading from a sensor
      return 25.0 + Float (Ada.Calendar.Clock mod 10);
   end Read_Temperature;
end Sensor;

3. Implementing the Processing Unit

Create a package for processing the temperature data.

-- processor.ads
package Processor is
   procedure Process_Temperature;
end Processor;
-- processor.adb
with Sensor;
with Ada.Text_IO;

package body Processor is
   procedure Process_Temperature is
      Temperature : Float;
      Threshold   : constant Float := 30.0;
   begin
      Temperature := Sensor.Read_Temperature;
      Ada.Text_IO.Put_Line("Current Temperature: " & Float'Image(Temperature));
      if Temperature > Threshold then
         Ada.Text_IO.Put_Line("Alert: Temperature exceeds threshold!");
      end if;
   end Process_Temperature;
end Processor;

4. Creating the Main Program

Create the main program to integrate the sensor and processor.

-- main.adb
with Processor;

procedure Main is
begin
   loop
      Processor.Process_Temperature;
      delay 1.0;  -- Simulate periodic reading every second
   end loop;
end Main;

Explanation

  • Sensor Package: Simulates reading temperature data.
  • Processor Package: Processes the temperature data and checks against a threshold.
  • Main Program: Continuously reads and processes temperature data, simulating a real-time system.

Practical Exercises

Exercise 1: Extend the System

Modify the system to include a logging mechanism that records temperature readings to a file.

Solution

  1. Create a logging package.
  2. Modify the processor to log data.
-- logger.ads
package Logger is
   procedure Log_Temperature(Temperature : Float);
end Logger;
-- logger.adb
with Ada.Text_IO;
with Ada.Calendar;

package body Logger is
   procedure Log_Temperature(Temperature : Float) is
      File : Ada.Text_IO.File_Type;
   begin
      Ada.Text_IO.Open(File, Ada.Text_IO.Append_File, "temperature_log.txt");
      Ada.Text_IO.Put_Line(File, Ada.Calendar.Clock'Image & ": " & Float'Image(Temperature));
      Ada.Text_IO.Close(File);
   end Log_Temperature;
end Logger;
-- processor.adb (modified)
with Sensor;
with Ada.Text_IO;
with Logger;

package body Processor is
   procedure Process_Temperature is
      Temperature : Float;
      Threshold   : constant Float := 30.0;
   begin
      Temperature := Sensor.Read_Temperature;
      Ada.Text_IO.Put_Line("Current Temperature: " & Float'Image(Temperature));
      Logger.Log_Temperature(Temperature);
      if Temperature > Threshold then
         Ada.Text_IO.Put_Line("Alert: Temperature exceeds threshold!");
      end if;
   end Process_Temperature;
end Processor;

Exercise 2: Add a Cooling System

Implement a cooling system that activates when the temperature exceeds the threshold.

Solution

  1. Create a cooling system package.
  2. Modify the processor to activate the cooling system.
-- cooling_system.ads
package Cooling_System is
   procedure Activate;
end Cooling_System;
-- cooling_system.adb
with Ada.Text_IO;

package body Cooling_System is
   procedure Activate is
   begin
      Ada.Text_IO.Put_Line("Cooling system activated.");
   end Activate;
end Cooling_System;
-- processor.adb (modified)
with Sensor;
with Ada.Text_IO;
with Logger;
with Cooling_System;

package body Processor is
   procedure Process_Temperature is
      Temperature : Float;
      Threshold   : constant Float := 30.0;
   begin
      Temperature := Sensor.Read_Temperature;
      Ada.Text_IO.Put_Line("Current Temperature: " & Float'Image(Temperature));
      Logger.Log_Temperature(Temperature);
      if Temperature > Threshold then
         Ada.Text_IO.Put_Line("Alert: Temperature exceeds threshold!");
         Cooling_System.Activate;
      end if;
   end Process_Temperature;
end Processor;

Conclusion

In this case study, we developed a simple embedded system using Ada. We covered the basics of reading sensor data, processing it, and triggering alerts. We also extended the system with logging and a cooling mechanism. This example demonstrates how Ada's features can be effectively used in embedded systems to ensure reliability, safety, and real-time performance.

Summary

  • Embedded systems have unique constraints and requirements.
  • Ada provides strong typing, concurrency support, and low-level programming capabilities suitable for embedded systems.
  • Practical implementation of a temperature monitoring system, including sensor reading, data processing, logging, and cooling system activation.

By completing this case study, you should have a solid understanding of how to approach embedded system development using Ada and be prepared to tackle more complex projects in the future.

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