As embedded systems grow in complexity and feature density, their software architecture often involves multiple tasks or threads working together to accomplish real-time objectives.
These tasks must synchronize and share data reliably, predictably, and efficiently. This brings us to a fundamental aspect of embedded system design—Inter-task Communication (ITC).
From sensor data collection and event handling to logging and system coordination, inter-task communication in embedded systems is critical for ensuring modularity, responsiveness, and safety. However, achieving efficient ITC isn't as simple as passing data from one function to another. It involves considerations like:
- Data consistency across tasks
- Real-time responsiveness
- Buffering and overflow control
- Memory constraints
- Persistence and fault tolerance
- One task might read sensor data.
- Another could process that data.
- Yet another might log it or send it over a network.
- Looks up all interested subscribers
- Invokes their handlers with the message
- Event notification systems (e.g., button press, system alert)
- GUI or HMI event propagation
- Sensor data updates to multiple consumers (e.g., display, logger, cloud)
- Sender creates a message and enqueues it.
- Receiver task waits for or periodically checks for new messages.
- Messages are processed in FIFO order.
- Command handling between application and protocol stack
- Task-to-task control messages (e.g., state change requests)
- Buffering incoming data for asynchronous processing
- Head (write position)
- Tail (read position)
- UART or serial port drivers
- ADC or DMA buffering
- Audio or video streaming
- Log collection buffers
- Multiple producer/consumer support
- Overflow detection and counters
- Optional locking mechanisms
- DMA-safe variants for high-speed use
- Messages are written to storage in a queue format
- Index pointers track the write/read positions
- Power-fail safe techniques (like journaling) prevent corruption
- Event logging in industrial systems
- Telemetry data buffering for IoT devices with intermittent connectivity
- Fault message retention in automotive or medical devices
- Support for NOR flash, NAND, and SD cards
- Power-failure-safe write techniques
- Configurable message size and wear leveling
- Integration with file systems or raw block access
In this article, we’ll explore four proven ITC mechanisms widely used in embedded development—Dispatcher, Message Queue, Ring Buffer, and Storage-Backed Queue—and how RAPIDSEA Suite provides robust, production-grade implementations for each.
Why Inter-Task Communication Matters
In a typical embedded application, tasks are divided based on functionality:
These tasks cannot work in isolation—they need to pass messages, share buffers, or signal events. Poorly managed communication can result in Race conditions, Data corruption, Task starvation, Missed deadlines and Increased power consumption.
Hence, choosing the right ITC mechanism and using it effectively is crucial for system stability and performance.
Dispatcher – Publish-Subscribe Mechanism
A Dispatcher enables a publish-subscribe communication model, where multiple tasks subscribe to specific message types or topics. When a message is published, the dispatcher automatically delivers it to all registered subscribers.
This decouples the sender from receivers, allowing greater modularity and flexibility.
How It Works
Each task registers a callback or handler for specific message types.
When a task publishes a message, the dispatcher:
Subscribers process the message concurrently or in sequence.
Advantages
some of the advantage dispatcher provides are Loosely Coupled Architecture - Sender doesn’t need to know who receives, Supports One-to-Many Communication - Ideal for event broadcasting and Scalable - Easily extendable with new subscribers or message types.
Use Cases
In RAPIDSEA
RAPIDSEA includes a lightweight dispatcher framework that supports dynamic registration, priority-based delivery, and real-time safe handling, making it ideal for modular embedded software designs.
Message Queue – Point-to-Point Messaging
A Message Queue allows tasks to send and receive structured messages asynchronously. Unlike dispatcher, this is typically a one-to-one communication pattern.
Messages are placed into a queue by the sender and popped out by the receiver task when ready to process them.
How It Works
Advantages
Some of the benefits of using message queue are Thread-Safe as Most implementations include mutex or atomic protection, Non-Blocking Options enabling Sender post without waiting and receiver can block or poll and finally providing Deterministic Behavior that is Ideal for real-time applications.
Use Cases
In RAPIDSEA
The RAPIDSEA message queue is a real-time optimized, thread-safe module that supports both blocking and non-blocking operations. It includes features like message prioritization and timeouts, suitable for use in RTOS or bare-metal environments.
Ring Buffer – Continuous Stream Handling
A Ring Buffer (or Circular Buffer) is a fixed-size buffer designed for streamed data—perfect for continuous producer-consumer scenarios.
As the producer writes to the buffer, the consumer reads from it—both pointers wrap around to the beginning when they reach the end.
How It Works
Fixed-size array with two pointers:
Data is written at the head, read at the tail
Wrap-around ensures efficient use of space
Advantages
The advantages of leveraging Ring buffers are that they are Fast and Deterministic with No dynamic memory, all operations are O(1). They are ideal for Streaming Data Like UART, SPI, or sensor feeds and have very Minimal Overhead as are Simple logic and no heap dependencies.
Use Cases
In RAPIDSEA
RAPIDSEA’s ring buffer module includes:
Storage-Backed Queue – Non-Volatile Messaging
A Storage-Backed Queue extends the message queue concept by backing the queue in non-volatile memory, such as NOR flash or SD card. This allows messages to persist across reboots or power failures.
How It Works
Advantages
These Storage backed queues are Crash Resilient as the Messages survive unexpected resets. They can offer Large Capacity since they store in flash more messages than RAM allows. They are Suitable for Low-Power Systems as Tasks can sleep while messages accumulate.
Use Cases
In RAPIDSEA
RAPIDSEA offers a modular storage-backed queue with:
Why Choose RAPIDSEA for Inter-Task Communication
Benefits of RAPIDSEA ITC Mechanisms
RAPIDSEA Suite is a modular, field-proven platform built for real-time embedded applications. All four ITC mechanisms discussed—Dispatcher, Message Queue, Ring Buffer, and Storage-Backed Queue—are Optimized for Performance - Minimal latency, low memory footprint, Thread-Safe - Designed for use with RTOS and bare-metal and highly Portable - Compatible with major MCUs and toolchains. Further the modules are Scalable - Suitable for low-power devices to high-end SoCs and Field-Proven - Used in products across automotive, industrial, healthcare, and consumer domains.
Conclusion
Robust and efficient inter-task communication is vital to embedded software design. Depending on the use case—whether it's event broadcasting, message exchange, streaming data, or persistent logging—selecting the right ITC mechanism can significantly enhance system performance, modularity, and reliability.
With RAPIDSEA’s ready-to-integrate components for Dispatcher, Message Queue, Ring Buffer, and Storage-Backed Queue, embedded developers can build communication-aware systems that are modular, responsive, and production-ready.