Docker or Development Container are great for isolation. And they work very well with things outside which are TCP/IP based. But most debug probes are USB only. Docker container don’t work well with USB. In Remote Debugging with DevContainer and VS Code, I showed how to use USB based debug probes. I demonstrated using them with an IP connection. In this article I show how Windows USB devices can be used from a container, with the help of usbipd.
I recently upgraded from Win10 to Win11. Windows 10 was not great for building performance compared to Linux. And I feel that with Windows 11 things got worse too.
Dev Container in VS Code uses docker-based environments. This enables me using a full-featured development environment, with isolated dependencies. This is especially very useful for development in the embedded systems space. There I have to use many different SDKs, toolchains and libraries. Using Dev Containers is super easy. But file I/O operations with building etc/is not that great.
The solution is to use a Docker Volume with VS Code and Dev Container:
Today’s projects and systems get more and more complex. Many systems include multiple MCUs, connected with a field bus or network, for example CAN. For example there can be up to 70 CAN nodes in modern cars. Such larger and connected systems are a challenge for debugging.
Traditional hardware debugging requires a hardware debug probe, connected with a dedicated SWD/JTAG debug cable to the target device. This needs dedicated pins on the target device plus physical access to the device itself. In many cases, this is not possible in the final product. The hardware debug probes, cables, pins and high speed signals are costly. And worse they can introduce new problems and are prone to interference.
If there is a field bus like CAN connecting all the MCUs, why not use it for hardware debugging? Hardware debugging meaning programming the FLASH memory, halt the MCU, inspect the memory and registers, and step through the code?
Cortex-M Hardware Debugging over CAN
Yes, we can! With the help of a rather unknown hardware feature on ARM Cortex-M devices. We can use the ARM DebugMonitor Interrupt to control and debug the target system. As we would use a JTAG/SWD connection. Instead, we use the CAN bus :-).
Usually, I run applications in the micro-controller FLASH memory. But for a CI/CD or testing environment that is not the best choice.
It is possible to have a ‘RAM target’, where the application is running in RAM instead of FLASH memory. This has the advantage not to ‘wear-out’ the FLASH memory. Plus loading and running in RAM is faster. This makes having RAM targets especially useful for testing.
In this article I’m using the NXP LPC55S16-EVK board, but any other target or board is applicable.
This is the second part describing how to use DevContainer for embedded applications with VS Code.
In Optimizing Embedded Development with VS Code and DevContainer I use VS Code with a docker ‘development’ container. The container is created with a recipe to install the development tools and SDK. With VS Code and DevContainer I have the same developer experience as I would develop locally on the host.
One thing not addressed in that earlier article is debugging. Using USB debug probes like a SEGGER J-Link or NXP MCU-Link is a challenge inside a container. This applies to any other debug probe as well.
The solution is to transform an USB based debug probe into one with a network connection:
Embedded System have a lifetime of 10 or 15 years. During that time the software and tools has to be maintained. This can be very challenging. Who knows if that compiler or tool used is still available in 10 years from now? Additionally installing and configuring the tool chain and environment for a new team member is difficult. Even worse: using a different host operating system for the cross development can produce different results or introduce issues.
VS Code running with DevContainer
One solution for all these problems is to use Docker images and containers. I can pack all the necessary tools and software into a virtual environment and container. But developing inside a container comes with many challenges. In this article I’ll show how Visual Studio Code or VS Code makes working with containers very easy. In this article I show how easy it is to use modern development tools and methodologies for embedded development.
NXP has released a new version of the LinkServer software. This is a utility for debugging and using scripting for a wide range of devices and debugging probes. It includes support for the MCU-Link, LPC-Link2, on-board and CMSIS-DAP based debug probes with the ‘LinkFlash’:
Programming with LinkFlash
With the new release, it includes a graphical user interface (GUI) for flash programming. It also includes erasing, verifying, recovery, and saving the memory to a file.
SEGGER has released a new version of their J-Link tools suite. That suite includes the J-Run utility which loads, executes and monitors the output of the target. Output can be with RTT (Real-Time Transfer) or semihosting. This makes it useful for automated tests with CMake and CTest:
CTest with J-Run
What has been added from the V7.98g release is the ability to send arguments to the running application using the --args command, for example with CMake/CTest:
set (RUNNER_CTEST_COMMAND "$ENV{SEGGER_PATH}/JRun" --verbose --device LPC55S16 --silent --rtt -if SWD)
add_test( NAME Led_1 COMMAND ${RUNNER_CTEST_COMMAND} --args "Led_1" ${TEST_EXECUTABLE} )
Like applications running on the host, I can now pass arguments to the running application. This is useful to set up the target, or to tell which kind of tests to run.
One key element of a CI/CD pipeline is the automatic testing phase: whenever I check in new source code or manually trigger it, I can run a test suite to make sure that the changes do not break anything. For this, I have to run automated tests. For an an embedded target, it means that I have to run some tests on the board itself too.
The MCU-Link is a small and inexpensive $10 CMSIS-DAP debug probe from NXP. It can work with OpenOCD, but has better target support using the NXP LinkServer which implements a gdb server. This makes it an ideal combination for scripting or automated testing.