Some time back, I gave a presentation that included an overview of the Git version control system. I still occasionally get asked why Git should be used instead of Subversion, as it seems harder at first. Most developers don’t really understand Git until they have used it for awhile, and then they will have an “aha moment.” There are 3 features of Git that are especially interesting to me:
Recently I needed to calculate NAND partition tables for a project where we will be supporting a number of different flash parts from 500MB to 2GB. I first tried this in a spreadsheet, but found it difficult to work easily with hex numbers and do the calculations I needed. I then looked into options for formatting text in columns from a program and found the nice text/tabwriter Go library. With a few lines of code, I was then able to get the below output, which is quite easy to read. The only tricky part was figuring out that for right justified data, you need to:
Why Docker? When using OE to build software for products, we often run into the scenario where software needs to be built using the same version of OpenEmbedded over the course of several years. Production builds need to be predictable. We’ve also observed that old versions of OE often break as new Linux distros come out. This is just the result of the complexity of building tool chains. Additionally, for predictable builds you really don’t want to be changing the build OS. This requirement automatically rules out Arch Linux, Debian Unstable, Gentoo, etc as production build machines. Additionally, having developers debug OE build issues on varying workstation distributions is frustrating and time consuming.
Go has a pretty neat development environment, and its helpful to set up a standard GOPATH on your workstation up front. This is what I do:
Now, after you log in, you can do things like:
In the quest for technologies that work well for embedded Linux systems, I recently gave Go another try. The last time I tried this was very early on and there were some floating point issues on ARM that appear to be fixed now. Having spent a few days porting an existing application to Go, there is a lot to like about Go.
With the explosion of IOT (Internet of things), there are now more technologies we can use to build systems. In reality, we’ve been doing IOT for years. We’ve been networking devices for a long time. We’ve been collecting data from remote nodes. This is nothing new, but what the IOT movement brings to the table is technologies that are much lower cost, and more standardized. Two of these technologies are MQTT and CoAP. Both very interesting, and very useful. Recently, I helped a system manufacturer think through the architecture of a system with the following requirements:
Recently, I sent a survey to the OpenEmbedded and Yocto mail lists asking a series of questions about how they use OE. 38 people responded. The average number of years using OE is 4.8 years.
One of the common things we do during Linux kernel development is move a series of patches from one kernel version to a similar version (say Linux 4.1 to 4.1.12). This is required as new stable versions of particular kernel version are released. One approach is to merge, but then your changes are mixed in with upstream commits and are more difficult to manage. Git rebase offers a convenient way to move a set of patches. In the following example we have a series of changes we made (or patches we applied) on top of the 4.1 kernel.
Recently, I needed to enable the eject command in BusyBox for an OpenEmbedded (Yocto) based project. Below is a way to do this in a fairly painless way:
I’ve already written about using autotools and qmake in OE. With recent projects, we’re using CMake to build most C/C++ components. Like any good tool, CMake has a learning curve, but it seems to do its job quite well. Below are examples of a CMake build file, and corresponding OE recipe.
Read More »Best practices for using CMake in OpenEmbedded/Yocto