I was working with a device that used Atmel SAMA5D3x MCU. Sometimes the devices needed to be re-flashed which required putting the MCU to programming mode. However, the device enclosure needed to be opened and also a jumper wire was needed to do this. Then I realized that it would be possible to enter the programming mode directly from Linux by manipulating boot sequence controller registers in the MCU. Writing a dedicated device driver for this seemed like an overkill so I wrote a simple utility application with mmap instead.
Recently I was working on an embedded Linux IoT device that communicated with cloud using MQTT protocol. The software in the device was divided into multiple applications that also required interprocess communication. We ended up using MQTT also for the local communication, and it turned out to be a good decision. Continue reading “Using local MQTT broker for cloud and interprocess communication”
Even though I work with C/C++ projects that are not related to Qt technology, QtCreator has become my main code editor. Here I explain some of the main reasons why I prefer it over other alternatives. Continue reading “My editor of choice for C/C++: QtCreator + FakeVim”
A while back I read the Working Effectively with Legacy Code by Michael C. Feathers. The book focuses on strategies and approaches to get existing untested legacy code covered by unit tests.
The book also includes more than twenty dependency-breaking techniques that can be used for new code as well to make it easily testable in the first place. Here I have picked three of the techniques that I have personally found most useful.
- Interfaces to abstract implementation
- Extract and override call
- Expose static method
Trusted platform module (TPM) is a secure element that can be used to securely generate and store keys. It has many possible uses, one of which is encryption of sensitive data. This article describes how to use TPM on Linux environment to encrypt different types of data, how to encrypt filesystem partitions and how to bind the encryption with device state.
In the true open-source spirit, the authors of some great Linux kernel books have decided to make these books freely available for everyone. They are good material for anyone interested in the Linux kernel, and also a good reference for professionals working with the kernel. At least I have personally found these books very useful.
Rootwait is a Linux kernel command line parameter that makes the kernel wait (indefinitely) for a root device to show up. This can be useful for devices that are detected asynchronously such as USB or MMC medias. This post, however, is not really about rootwait. Instead, it is about something that every programmer have and will encounter.
Continue reading “The missing rootwait”
Usually when working with USB thumb drives, memory cards and hard drives, the partitioning can be easily done just by plugging them to a Linux (or Windows) PC and using a partitioning application such as fdisk. However, with embedded devices it is sometimes more practical to write the partition table to a file instead of directly writing it to the memory device. This can be the case with embedded MMC (eMMC) memories which are soldered directly to the device and cannot be connected to a PC for partitioning.