OSMailbox

RTOS Mailbox Example

Overview

This application demonstrates inter-task communication using mailboxes in a real-time operating system (RTOS). The program creates two tasks that communicate through a shared mailbox mechanism, showcasing how tasks can send and receive messages in a multi-threaded environment.

Application Description

The Mailbox Example application consists of two main tasks:

1. UserMain Task - The primary task that waits for messages from other tasks
2. MyTask - A secondary task that periodically sends messages to the mailbox

Program Flow

1. The application initializes the system and enables network connectivity
2. A mailbox object (MyMailbox) is created and initialized
3. Two tasks are created with different priorities:
   • UserMain runs at main priority level
   • MyTask runs at main priority + 1 (higher priority)
4. The tasks communicate through the mailbox using a producer-consumer pattern

Task Behavior

UserMain Task

• Continuously waits (pends) on the mailbox for incoming messages
• When a message is received, it prints the message value
• Increments the received message value before the next iteration
• Handles error conditions when message reception fails

MyTask

• Runs in an infinite loop with a 3-second delay between iterations
• Posts a message containing a uint8_t value to the mailbox
• Prints status information when posting messages

Key Features

• Inter-task Communication: Demonstrates safe message passing between tasks
• Blocking Operations: Shows how tasks can block waiting for messages
• Error Handling: Includes proper error checking for mailbox operations
• Debug Output: Provides serial port output for monitoring program execution
• Network Integration: Waits for active network before starting main operations

Technical Details

Data Structures

• OS_MBOX MyMailbox - The mailbox object for inter-task communication
• uint32_t MyTaskStack[USER_TASK_STK_SIZE] - Stack allocation for MyTask
• uint8_t myMsg - The message data passed between tasks

RTOS Functions Used

• OSTimeDly() - Task delay function
• MyMailbox.Init() - Mailbox initialization
• MyMailbox.Post() - Send message to mailbox
• MyMailbox.Pend() - Wait for message from mailbox
• OSSimpleTaskCreatewName() - Task creation with naming

System Functions

• init() - System initialization
• EnableSystemDiagnostics() - Enable system diagnostic features
• WaitForActiveNetwork() - Wait for network connectivity

Output

The program outputs status messages through the serial debug port, which can be monitored using terminal programs like MTTTY. The output shows:

• When UserMain is waiting for messages
• When MyTask posts messages to the mailbox
• The received message values
• Any error conditions that occur

Build Requirements

• RTOS system with mailbox support
• Serial debug port capability
• Network stack (optional, used for initialization timing)

Usage

1. Compile and flash the program to your target device
2. Connect a serial terminal to the debug port
3. Monitor the output to observe the mailbox communication pattern
4. The program runs indefinitely, demonstrating continuous inter-task messaging