Lab05_Adding_Multiple_Tasks

Lab 05: Adding Multiple Tasks

Overview

This lab builds upon previous labs by focusing on managing multiple tasks in a FreeRTOS environment. You will learn how to create, prioritize, and schedule multiple tasks to work together effectively in a real-time operating system.

Objectives

• Create and manage multiple tasks in a FreeRTOS environment
• Understand task priorities and their effect on scheduling
• Implement task synchronization techniques
• Monitor task performance and resource usage
• Practice effective multi-tasking design patterns

Hardware Requirements

• TM4C123GH6PM LaunchPad Evaluation Kit
• USB cable for programming and debugging
• Optional: Additional LEDs or peripherals for visual feedback

Software Requirements

• Keil µVision IDE
• FreeRTOS kernel (included in the project)

Project Structure

• main.c: Main application code with task definitions and initialization
• tm4c123gh6pm.h: TM4C123 hardware definitions
• RTE/: Run-Time Environment folder containing FreeRTOS configuration

Getting Started

1. Open the lab5.uvprojx file in Keil µVision
2. Review the main.c file to understand the task structure
3. Build the project using F7 or the Build button
4. Flash the program to your TM4C123 board
5. Observe the behavior of multiple tasks running concurrently

Implementation Details

This lab demonstrates:

1. Creating multiple tasks with different priorities using xTaskCreate()
2. Controlling task execution through priorities
3. Managing shared resources between tasks
4. Implementing periodic tasks with different execution frequencies
5. Using task utilities such as vTaskDelay() and vTaskDelayUntil()

Expected Behavior

• Multiple tasks execute according to their assigned priorities
• Higher priority tasks preempt lower priority tasks when needed
• Tasks demonstrate cooperation by yielding control when appropriate
• The application shows predictable real-time behavior

Synchronization Methods

This lab explores various ways tasks can be synchronized:

1. Priority-based Preemption: Higher priority tasks interrupt lower priority tasks
2. Time Slicing: Tasks of equal priority share CPU time
3. Explicit Yielding: Tasks voluntarily give up processor time
4. Timed Delays: Tasks suspend themselves for specific time periods

Task Management Best Practices

• Assign priorities based on task importance and deadlines
• Keep critical sections short to avoid blocking other tasks
• Use appropriate delay mechanisms for periodic tasks
• Be mindful of stack usage for each task
• Consider using task notifications for simple task-to-task signaling

Troubleshooting

• Tasks Not Running: Verify priority assignments and ensure the scheduler is started
• Stack Overflow: Increase stack size for tasks that use more stack space
• Timing Issues: Check delay calculations and timer tick configuration
• System Hangs: Look for potential deadlocks or priority inversion situations

Extending the Lab

Try these extensions to deepen your understanding:

1. Add more tasks with different behaviors and priorities
2. Implement a task that monitors and reports on other tasks' performance
3. Experiment with different scheduling policies by modifying FreeRTOSConfig.h
4. Add resource sharing between tasks with proper protection mechanisms

References

• FreeRTOS Task Management
• TM4C123 Datasheet
• Task Priorities and Scheduling in FreeRTOS