--- title: "Getting Started With Zephyr: Using GDB To Fix a Driver Bug" url: https://daily.dev/posts/getting-started-with-zephyr-using-gdb-to-fix-a-driver-bug-b1e5k4qsg source_url: https://www.embeddedrelated.com/showarticle/1753.php type: article source: "EmbeddedRelated" published: 2026-05-31T07:47:57.833Z updated: 2026-06-04T02:17:09.259Z tags: ["embedded", "stm32"] reading_time: 10 upvotes: 0 comments: 0 language: 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. # Getting Started With Zephyr: Using GDB To Fix a Driver Bug **[EmbeddedRelated](https://daily.dev/sources/embeddedrelated)** · 10 min read · 0 upvotes · 0 comments ## Summary A walkthrough of debugging a TSL2591 light sensor driver initialization failure on an STM32L4 Discovery IoT node running Zephyr RTOS. Using `west debug` and GDB, the author traces the failure from the sensor init function down through Zephyr's I2C subsystem into the STM32 I2C controller driver. Disabling compiler optimizations (`CONFIG_NO_OPTIMIZATIONS=y`) makes stepping reliable. Inspecting the `data` struct reveals `is_nack=1` after a software reset write — the device doesn't ACK immediately after reset. The fix treats the post-reset NACK as non-fatal by ignoring the return code, consistent with Adafruit's Arduino driver and the Linux kernel driver. The fix was submitted as a PR and accepted upstream into the Zephyr project. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Simplifying Embedded System Design with a Modern Software Ecosystem](https://daily.dev/posts/simplifying-embedded-system-design-with-a-modern-software-ecosystem-jr0ummxbk) · Embedded.com · 0 upvotes · 0 comments --- Tags: [#embedded](https://daily.dev/tags/embedded), [#stm32](https://daily.dev/tags/stm32) [View this post on daily.dev](https://daily.dev/posts/getting-started-with-zephyr-using-gdb-to-fix-a-driver-bug-b1e5k4qsg)