If doing embedded development, then the debugging solution is probably the most important single tool in the development chain. Because very debugging probe has its pros and cons, I usually have at least three different debug probes on my desk, simply to get the job done in all aspects.
What is true for the hardware debugging probes, is true for the gdb client and server side. I’m using mostly the P&E, SEGGER and CMSIS-DAP plugins (e.g. NXP LinkServer) and OpenOCD from the Eclipse IDE side. But there are more choices, for example pyOCD.
pyOCD and Python
So far I ave, I avoided to use pyOCD for several reasons, mostly because it is centered around ARM only I had issues to get it working because of the Python dependency. But as my usual Triumvirate of debugging solutions failed on something around semihosting, I wanted to give pyOCD another chance.
pyOCD is a Python based debugging tool for ARM Cortex microcontroller. pyOCD comes with many useful features, like command line flash programming , semihosting and ARM ITM SWO printing.
While Python is getting more popular, Python as an environment can be tricky, as experienced in classroom environments with students and on my machine too. I recommend to try with a ‘clean’ python environment: just one version installed or clearly isolated. My earlier attempts to get it working on Windows with Eclipse failed, so I tried to get it working with the latest release, and finally: it worked with using Python v3.10.9 with pip v23.0 and pyOCD v0.34.3 :-).
As Eclipse I used the MCUXpresso IDE v11.7.0, but the steps should work for any recent Eclipse version.
On a command line shell, install it with the pip package manager:
python3 -m pip install -U pyocd
Now the important part is the message at the end of the installation:
I really don’t like cluttering my PATH environment variable, so adding this to my PATH is not an option. Instead: remember (copy-paste) that above path to the Scripts folder, we need that one later.
PEMICRO Debug Probes
PyOCD supports CMSIS-DAP (e.g. NXP Linkserver) and SEGGER J-Link based probes. To have support added for P&E debug probes (Multilink, etc), you need to install another package (see https://github.com/pyocd/pyocd-pemicro):
python3 -m pip install pyocd_pemicro
If not using a P&E debug probe, this step can be skipped.
Eclipse Embedded CDT Plugin
Eclipse Embedded CDT has integrated the GNU ARM Eclipse plugins, developed by the famous Liviu Ionescu. The easiest way to get them installed into Eclipse is using the Eclipse Marketplace (menu Help > Eclipse Marketplace).
Then install the Eclipse Embedded C/C++ plugin:
After that, restart the IDE as asked at the end of the installation.
pyOCD Eclipse Settings
Remember that PATH thing earlier during pyOCD installation? I have to tell Eclipse where pyOCD is installed, because I did not want to clutter the global PATH. I recommend to set this up in the IDE using the global settings (Menu Window > Preferences):
If needed, this can be configured on a project or workspace level too. I prefer the above way to set it on an IDE level.
Eclipse Debug Launch Configuration
To debug a project in Eclipse, I need a launch configuration. As precondition, I have a project and built the binary (ELF/Dwarf) file successfully.
Below the steps to create a launch configuration for pyOCD in Eclipse.
First, select the project int the project explorer view and use the menu Run > Debug Configurations:
Then double-click on the GDB PyOCD Debugging group:
This creates a launch configuration with most fields correctly filled out, because I had selected that project in the first step:
I recommend saving the launch configuration file and settings in the project: That way it easily can be stored in a version control system like git.
The most important settings are in the ‘Debugger’ Tab:
In the debug probe drop-down I can select any attached debug probe (P&E, CMSIS-DAP or J-Link):
Tick ‘Override Target’ and select the target used (in my case the FRDM-K22F board):
Finally, press ‘Debug’.
The nice thing with pyOCD is, that without any special settings, it recognizes FreeRTOS.
Overall, debugging seems to work pretty well. With using semihosting there is some lagging.
I’m really glad that finally I have pyOCD working. This gives me yet another angle and debugging view in Eclipse. Compared to OpenOCD it is easier to setup, but comes with the dependency on Python and is ARM only. The pyOCD web site lists 70 ARM Cortex-M devices supported, far less what solutions support. Comparing pyOCD with OpenOCD: OpenOCD supports far more different devices and non-ARM ones, but is more complex and slower in my view, with OpenOCD as a ‘large open source community project’. pyOCD (driven by Chris Reed) on the other side seems to have more frequent updates and features added, for example RTT support added recently in v0.33.0.
But at the end, the best thing is that there are choices: pick what fits best your needs! And have at least three different hardware debug probes on your desk 😉
Happy debugging 🙂
- pyOCD web site: https://pyocd.io/
- pyOCD on Github: https://github.com/pyocd/pyOCD
- GNU MCU Eclipse (now Eclipse Embedded CDT): https://eclipse-embed-cdt.github.io/
- PEMICRO pyOCD: https://github.com/pyocd/pyocd-pemicro
Since 2020, the Embedded CDT address is .
I probably will still end up on the old pages/links for a long time 😉
That’s unfortunate. Probably I should add redirects to all pages…
I only imagine what will happen should I ever need to change mcuoneclipse to different webpage….
nah, that does not sound right 😉
thank you for the information
You are welcome! Are you planning to use pyOCD or do you already use it?
RTT mentioned at the end is also present in openocd since version 11.0.
BTW new version 12.0 is out since two weeks
Yes, just saw that finally there is a 12.0 release, but had no chance yet to try it out.
Have you measured speed openocd vs pyocd? I can not find any real data that supports the claim that pyocd is faster vs openocd. Only one place where I found any results is here:https://github.com/rgrr/yapicoprobe#optimizations and it looks like openocd is faster and more reliable.
Here it is: https://github.com/xpack-dev-tools/openocd-xpack/releases/tag/v0.12.0-1
I’m wondering why you got the FreeRTOS view and I don’t… Does this view really has something to do with pyOCD or some CMSIS pack you installed? Or is it some lack of support for my RP2040? (BTW: multicore support for the RP2040 of gdb with pyOCD 034.3 or OpenOCD 0.12 is really bad).
Something to add: instead of specifying the complete path of pyocd it should be enough if you are using “python -m pyocd”. python should know its way through its own configuration.
I don’t have any extra packs installed. But I do maintain a special version of FreeRTOS which has all the needed debug symbols present. That FreeRTOS is inside the McuLib, and you can see the project I used in this article on GitHub here:
I’m using the same McuLib with RP2040 too, see for example https://github.com/ErichStyger/mcuoneclipse/tree/master/Examples/RaspberryPiPico.
For the RP2040 I’m using the J-Link (see https://mcuoneclipse.com/2022/07/16/getting-started-raspberry-pi-pico-rp2040-with-eclipse-and-j-link/) and there I have all the views too.
Checked it but I think this will not work for me. I’m currently on the FreeRTOS SMP branch and if one looks at https://openocd.org/doc-release/doxygen/FreeRTOS_8c.html one will see that “tasks::pxCurrentTCB” is now a macro because of the two cores.
All other symbols OpenOCD requires are global.
BTW: debugging in the multicore configuration does not work with pyOCD because there is just the choice between either core0 or core1. So no way to start two gdb for the two cores. That’s what OpenOCD 0.12 does: it is starting two sockets, one for each core.
OpenOCD 0.11 from https://github.com/maxgerhardt/platform-raspberrypi does it more elegant: it opens one socket and shows two threads. So only one gdb is required to control the RP2040.
But no FreeRTOS display unfortunately with my configuration.
about ‘python -m pycocd’: this does not work for me 😦
Sorry, you are right. I’m using it that way from the command line, but my Eclipse debug configuration did not accept “python -m pyocd” and I did not recognize that.
I will check your McuLib from above.
For that FreeRTOS project, the library is embedded inside that project. The original library is here: https://github.com/ErichStyger/McuOnEclipseLibrary