--- title: Why did my microcontroller crash? | daily.dev description: A hands-on walkthrough of debugging a crashed ARM Cortex-M microcontroller running a marble game. Using GDB and VS Code with the cortex-debug extension, the... canonical: https://daily.dev/posts/why-did-my-microcontroller-crash--ibxxyejnh twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Why did my microcontroller crash? | daily.dev og:description: A hands-on walkthrough of debugging a crashed ARM Cortex-M microcontroller running a marble game. Using GDB and VS Code with the cortex-debug extension, the... og:url: https://daily.dev/posts/why-did-my-microcontroller-crash--ibxxyejnh og:image: https://api.daily.dev/og/posts/IbXxyeJNh.png og:image:alt: Why did my microcontroller crash? og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Why did my microcontroller crash? **[Artful Bytes](https://daily.dev/sources/artfulbytes)** · 19 min read · 0 upvotes · 0 comments ## Summary A hands-on walkthrough of debugging a crashed ARM Cortex-M microcontroller running a marble game. Using GDB and VS Code with the cortex-debug extension, the author connects to the debug probe without resetting the chip, reads CPU registers (PC, xPSR, hard fault status register, configurable fault status register) to identify a hard fault caused by an imprecise bus error — an out-of-bounds write to a frame buffer. The call stack is manually decoded from raw RAM contents and then verified via GDB backtrace, tracing the fault through count_pixel → plot_pixel → draw_ball → run → main. The root cause is drawing the ball before clamping its coordinates, allowing it to write past the end of the 1024-byte frame buffer. The post also covers stack corruption when writing off the top of the display, adding a custom hard fault handler to dump crash state over UART, and the simple one-line fix of moving the bounds check before the draw call. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [My device crashed in the field. 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