Three years ago I published “Debugging Failure: Check List and Hints” and unfortunately this article is one of the most popular ones: obviously debugging problems are very common. Debugging with GDB works usually fine, but if things are failing, then it can be hard to find the cause for it. Recently I have been asked to check some failures, so here are two more hints about what could go wrong…
Error while launching command: arm-none-eabi-gdb –version
When working and debugging a bootloader, debugging can be a challenge: During debugging the bootloader, a new binary gets loaded into the microcontroller address space which is unknown to the debugger. As soon as I step into the newly loaded binary, I only see assembly code, with that ugly “No source available” in Eclipse:
No Source Available, debugging in assembly
But wait: GDB is able to do pretty much everything you can imagine, so here is how to debug multiple binaries with GDB and Eclipse, and to turn the above into something which is easy to debug:
Sometimes things don’t go well, especially with bringing up a new board design. I always sweat blood that first minute when I try to connect with the debugger to a new design: Will it work? After the optical inspection, performing electrical tests (no shortcuts? voltage levels ok?) the inflection point is when I’m connecting the first time with the debugger to the new board: either it will properly connect and program the device (hurrah!) or it will fail and potentially difficult hours of investigations have to follow.
The reset and signal line of a microcontroller is probably the most important signal to a microcontroller. And if things go wrong, then a first thing to check is the reset line. So having control over reset is an important aspect for embedded development. You would think that if you download a program to a microcontroller, the debug probe would put the device into reset at the start with a short pulse like this:
In “A Processor Expert Component to Help with Hard Faults” I’m using a C handler with some assembly code, created with Processor Expert, to help me with debugging hard faults on ARM Cortex-M. Inspired by a GNU gdb script here, I have now an alternative way. As this approach is using the GDB command line approach, it works both with an Eclipse GUI and with using GDB in command line mode only :-).