Questions from students or readers of my articles are a great source for all kind of articles. And here is the ‘question of this week’: “What is realtime debugging”?
It’s a good question because the topic of ‘realtime’ and ‘debugging’ was a topic in the lectures this week. So this question gives me the opportunity to combine the two things of ‘realtime’ and ‘debugging’, I love it :-).
Debugging Setup
Coming out of a project meeting Friday evening, the following wisdom came to my mind:
“The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.” – Anonymous
What is a Sunday morning without a perfect breakfast? With a Sous-Vide cooker in the kitchen, this small research project is about preparing Eggs Benedict Sous-Vide style:
Egg Benedict
Instead creating a new project from scratch, often it is simpler to copy an existing Eclipse CDT project, then change it and go on. To copy-past the a project in Eclipse:
Copy of a project
Paste of Project
However, to make that process simpler, a few things have to be done right in the ‘source’ project first.
I’m a big fan of ‘low-and-slow’ cooking, and that’s why I love my BBQ Smoker. That smoker is great for Ribs, Brisket or Pulled Pork. But it is not ideal for other pieces of meat. After doing some research, this weekend I tried something differently: “Sous-Vide”. The result is delicious: this is by far the best steak I’ve ever cooked :-).
Beef Sous Vide
Some ARM Cortex-M have a DWT (Data Watchpoint and Trace) unit implemented, and it has a nice feature in that unit which counts the execution cycles. The DWT is usually implemented on most Cortex-M3, M4 and M7 devices, including e.g. the NXP Kinetis or LPC devices.
DWT Cycle Count Register (Source: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0489d/BABJFFGJ.html)
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:
Debugging with Symbolics
To me, one of the most frustrating things working with ARM Cortex-M cores are the hard fault exceptions. I have lost several hours this week debugging and tracking an instance of a hard fault on an ARM Cortex-M0+ device.
MCU on Eclipse 