7 easy-to-use and long-lasting tips for embedded system development

Transitioning into a formal embedded development engineer is a challenging journey that demands precision and control over every aspect of the system. Building highly reliable embedded systems involves a combination of well-structured development processes, rigorous testing, and continuous monitoring. In this article, I’ll share seven practical and long-lasting tips to enhance the reliability of your embedded systems and help detect abnormal behavior early on.

Tip 1 - Fill the ROM with a Known Value

Many developers assume their code will run flawlessly for years without issues. However, microcontrollers can sometimes jump out of the intended application space and execute unintended code. This may happen due to buffer overflows, incorrect pointers, or other unexpected events. If the memory is filled with default values like 0xFF, it becomes difficult to trace where the problem originated. To prevent this, you can use the FILL command in your linker script to populate unused ROM sections with a known pattern. Placing a fault handler at these locations allows the system to catch such errors and log critical information before a reset occurs.

Tip 2 - Check the Application’s CRC

CRC (Cyclic Redundancy Check) is a powerful tool for verifying the integrity of your firmware. While many systems check the CRC only during the initial load, it’s even more beneficial to perform this check at startup or periodically. This ensures that the application hasn’t been corrupted by power fluctuations, electrical noise, or flash corruption. By maintaining the CRC in memory, you can quickly detect and respond to any unexpected changes in the code.

Tip 3 - Perform a RAM Check at Startup

A solid system starts with verified hardware. At boot time, performing a simple RAM test by writing a known pattern and reading it back can help identify faulty memory modules. Even if the test passes, it gives you confidence that the hardware is functioning as expected. If the test fails, it signals a potential hardware issue, allowing the system to take corrective action or alert the user.

Tip 4 - Use a Stack Monitor

The stack is often overlooked but plays a critical role in system stability. A stack overflow can corrupt adjacent memory, leading to unpredictable behavior. Implementing a stack monitor that checks for changes in a predefined pattern between the stack and other memory areas can help detect stack overflows early. Most RTOSs and modern MCUs come with built-in stack protection features, but they are often disabled by default. Enabling them can save you from debugging complex and hard-to-reproduce bugs later.

Tip 5 - Leverage the MPU

The Memory Protection Unit (MPU) is an underused but powerful feature in many modern microcontrollers. It allows you to define memory regions with specific access rights, preventing unauthorized access or accidental overwrites. This is especially useful in multi-tasking environments where different processes need to be isolated. Using the MPU can significantly improve the robustness of your system and prevent crashes caused by invalid memory accesses.

Tip 6 - Build a Robust Watchdog System

A watchdog timer is one of the most effective tools for ensuring system recovery after a crash. A properly configured watchdog should be independent of the main application logic so that it continues to count down even if the system fails. You can implement advanced techniques like task-based watchdog resets or external watchdog processors to add multiple layers of protection. A strong watchdog system can save your system from being stuck in an unrecoverable state.

Tip 7 - Avoid Volatile Memory Allocation

While dynamic memory allocation (like malloc/free) is convenient in general-purpose computing, it can be problematic in embedded systems. Memory fragmentation and leaks are common pitfalls that can lead to system instability. Instead, using static memory allocation—preallocating buffers and data structures at compile time—can eliminate these risks. This approach provides more predictable performance and reduces the chance of runtime failures due to memory issues.

In conclusion, adopting these best practices can greatly enhance the reliability and robustness of your embedded systems. Whether you're working on a small microcontroller or a complex real-time system, these tips can help you build more stable and maintainable software. Remember, the goal is not just to make the system work, but to make it work reliably, even under unexpected conditions.