The Power of Post-Mortem Debugging for Embedded SystemsThe Power of Post-Mortem Debugging for Embedded Systems

For an embedded developer, few things are more frustrating than hunting down an elusive bug or performance issue in firmware, especially on remote devices with limited debugging access. You’re often left grasping for clues, scrounging through incomplete log data and struggling to reproduce intermittent failures. It can feel like solving a crime with no evidence left at the scene.

That’s where post-mortem debugging for embedded systems is a total game-changer. The core concept is to enable automated capture and storage of diagnostic “snapshots” on software crashes, errors, performance glitches, and other important anomalies. These snapshots provide key information on the device state that allows for retrospective debugging without needing a live debug connection to the device. This decouples the debugging process from the physical hardware, enabling effective debugging no matter where and when the issue showed up.

Observability on anomalies can be a game changer for edge device developers, offering both fleet-level overview and post-mortem debugging based on automatically collected snapshots. PERCEPIO

What can post-mortem debugging give you?

This approach can provide multiple kinds of debugging data, such as logs, event traces, and core dumps. For crash debugging, core dumps are indispensable. These provide selected parts of the RAM memory contents as well as processor registers, letting you inspect the call stack, local variables, and more in your IDE debugger just like halting on a breakpoint mid-execution. The contents of a core dump are usually configurable, and they can therefore be very compact—a few hundred bytes is often sufficient for crash debugging if based on the current thread stack pointer.

Related:Understanding Errors, Defects, & Bugs in Software Development

Tracing tells the story

But core dumps alone don’t always tell the whole story of what led to a failure. To get more information, you may include a software event trace that gives a detailed “film reel” of the runtime activity preceding the issue. This may include thread execution, system calls, and key application events, giving a rich history of the system behavior in the moments before things went awry. By keeping the event trace in a circular RAM buffer, the most recent history of events is always available and can be saved as part of the snapshot on errors or crashes.

Event trace data can be visualized with trace visualization tools to make it easier to analyze complex issues. This way you can diagnose the toughest problems, involving multiple events across different threads, timing issues, and resource starvation—all without needing an advanced debug probe and without needing a live debug connection to the device.

Some event tracing libraries also allow for highly efficient application logging, for example, by saving the strings using their address only (i.e., 4 byte per string on 32-bit systems) and providing a decoding tool that leverages the symbol information in the ELF file.

Related:5 Key Skills You Need to Build an Embedded Systems Career

Debug anywhere, over any interface

The real beauty of this post-mortem debugging approach is how seamlessly it works whether you’re in the lab or dealing with issues on devices deployed worldwide. Simple direct connections like UART get the job done locally. But for remotely deployed products, that same detailed diagnostic data can be relayed over any available connectivity channel—Wi-Fi, cellular, Bluetooth, you name it. As long as you have some way to output and collect the data, you’re set. On devices without continuous connectivity, the data can be stored on the device and provided when connected. 

For developers stuck fighting blind against obstructed, intermittent, or just plain bizarre embedded software issues, continuous observability and post-mortem debugging is a revelation. Instead of shooting in the dark, you get a comprehensive forensic record to quickly identify and resolve even the most elusive failure scenarios—no matter where in the world the device is located.