Build a firmware black box to diagnose embedded field resets

Short summary

Embedded devices that reset in the field leave no trace unless you build a firmware black box to capture diagnostic data (reset reason, watchdog events, stack margins, network state). This article explains how to design a compact persistent diagnostic subsystem and provides a pre-ship checklist. With field diagnostics, rare intermittent bugs become solvable; without them, debugging becomes guesswork.

• •Field resets without diagnostics delete evidence; a firmware black box preserves post-mortem data across reboots.
• •Start small: capture reset reason, uptime, firmware version, task health, stack margins, and network state in persistent storage.
• •Includes a pre-ship checklist covering watchdog strategy, HardFault handling, OTA state, and support-team-readable reports.

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