With debugging FreeRTOS applications in Eclipse, it is a big to have views available showing all the threads, queues, timers and heap memory allocation. One of the best Eclipse plugins are the one NXP provides for FreeRTOS: they are free of charge and give me pretty much everything I need. However, if you are not that familiar with FreeRTOS itself, here are a few tips to get more out of the plugins.
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 :-).
Good news for everyone using Eclipse, FreeRTOS and Percepio Tracealyzer: Percepio has released an Eclipse plugin which makes snapshot tracing very easy and convenient using the a GNU gdb debugger in Eclipse like Kinetis Design Studio:
P&E has a new version of their GDB/Eclipse debug plugins available on their Eclipse update site, and it comes with to great features: Real Time Expressions (show variables while target is running) and FreeRTOS thread awareness 🙂
For a CubeSat project we only have a single board available. But multiple universities and developers need to have access to that board for developing and debugging the firmware. We cannot easily ship around the board: that takes a lot of time and during shipment nobody can use the board.
There is a nice feature in the Segger J-Link software which allows to share the debug connection over the network: the J-Link Remote Server. It even works nicely between different networks without complicated firewall setup:
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.
The concept of Linux (Open Source, broad developer base and broad usage) is a success story. While there is a lot of diversity (and freedom) in the Linux world, Linux is Linux and again Linux :-). And the world has (mostly) standardized on Linux and its variants on the high embedded system side.
“The Linux Foundation Announces Project to Build Real-Time Operating System for Internet of Things Devices. Open source Zephyr™ Project aims to deliver an RTOS; opens call for developers to help advance project for the smallest footprint IoT devices.“
Ζεφυρος (Zephyros) is the Greek good of spring and the west wind. Obviously this inspired the logo for the Zephyr project:
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:
The Hexiwear docking station would have a nice feature: it has embedded a debug circuit (OpenSDA). That way I would not need an external debug probe to debug the Hexiwear. However, a debug probe is required to reprogram the docking station itself:
Repgrogramming the Mikroelektronika Docking Station
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.
For a university reasearch project I try to pair the Raspberry Pi 3 with a Mikroelektronika Hexiwear using BLE (Bluetooth Low Energy). Most of things worked after a lot of trial and error, but at a certain point I was stuck trying to write to send data from the Raspy to the BLE device.The Hexiwear BLE protocol description is very thin, so I ended up using a BLE sniffer to reverse engineer the protocol with Wireshark.
But one issue I have faced several times is that the board works fine while debugging and connected and powered by a host machine, but does not startup sometimes if powered by a battery or started without a debugger attached. I have found that the EzPort on the microcontroller is causing startup issues.
It seems to me that not many developers use hardware trace? ARM indicates that maybe only <5% of developers are using trace. Too bad! Why are all the ARM Cortex microcontroller vendors putting a powerful hardware (and complicated!) trace engine into their devices, if only few developers are using it? Seems like a waste of silicon and an unnecessary price adder? Well, hardware trace can be a life saver: Because only with hardware trace the most complicated bugs and problems can be solved. And maybe because only the best are using it ;-).
As a standard procedure, I add some console functionality to my embedded applications. That way I have a command line interface and can inspect and influence the target system. One interesting hardware feature of ARM Cortex-M is Single Wire Output (SWO): it allows to send out data (e.g. strings) over up to 32 different stimulus ports, over a single wire.