Mohammad Afaneh writes about the importance of firmware debugging experience and its difficulty:
Debugging is generally difficult, and it gets even more difficult for firmware applications and has more limitations compared with a mobile or web application.
This is due to a few factors, some of which are:
- Limited availability of resources for debugging. For example, some bugs are very difficult to diagnose using software breakpoints. In those scenarios, you would rely on hardware breakpoints and usually there is a limited number of hardware breakpoints for a specific architecture. This makes debugging complex bugs a challenging task.
- Time-dependency in real-time/time-critical applications. For example, setting breakpoints can interfere with the timing of operations. If a bug is timing-related, then the debugging process may even cause the bug to disappear!
- Challenges in setting up the debugging environment (cross-platform development environment). There is a variety of visual IDEs and integrated debuggers available, but for some scenarios you may need an automated debugging setup and this can prove to be a challenging task.
- High cost of some debugging hardware tools.
Fortunately, GDB is a widely available open source debugger with popular support and strong features:
- GDB supports a vast number of architectures including: ARM, x86, MIPS, and many more. Because of this, a firmware developer’s knowledge and expertise with GDB is potentially transferable across many projects.
- GDB is command-line based which gives it high flexibility and usability in debugging tasks that require some level of automation. This became especially true with the release of the Python API for GDB in GDB’s release version 7.0 (in 2011).
- GDB supports remote debugging. This is crucial for embedded systems where the development environment resides on an architecture different from the target system (e.g. developing on a Windows machine for an ARM-based target).
The article goes through an example of using the Nordic nRF52840 development kit. A number of resources are also provided for further reading.