Technical notes

Technical notes

Bazel AVR toolchain from scratch (no_legacy_features)

Even when you define your own cross compilation toolchain in Bazel, it still comes with a set of predefined, 'sane' defaults for the compilation and linking flags. But if you want to take full control over the generated commands, you can turn off all the default features, that are added

Writing BeagleBone internal eMMC from U-Boot, without SD card

BeagleBone has the possibility to load the bootloader using the serial console and xmodem. To do that lunch picocom with additional --send-cmd definition: $ picocom -b 115200 /dev/ttyUSB0 --send-cmd "sx -vv" If there is no available bootloader on the eMMC and the SD card is not available the device will

Workaround for stuck BeagleBone USB Ethernet gadget

The BaegleBone board seems to have some problem with USB Ethernet gadget not working correctly. It happens quite frequently that the the USB Ethernet device is not able to receive any packets, although transmission is still possible: root@beaglebone:~# ifconfig usb0 usb0 Link encap:Ethernet HWaddr 22:04:F8:8E:

Linux shared libraries with CMake and Bazel

A great introduction to shared libraries is available from Michael Kerrisk: * https://man7.org/conf/lca2006/shared_libraries/index.html A detailed analysis of shared libraries can be found in Ulrich Drepper's paper: * https://akkadia.org/drepper/dsohowto.pdf This paper is a must read if you want to understand

Using toolchains in custom Bazel C++ rules

After writing a sketch of own C++ rules, which you can find here: * https://ltekieli.com/writing-custom-bazel-c-rules/, we might extend this example with toolchain support. In order to not conflict with existing C++ toolchain implementation we need to define a new toolchain type using a special rule: toolchain_type( name

Writing custom Bazel C++ rules

Implementing a language support in Bazel can help one better understand the existing functionalities that this build system already provides. The migration process for Bazel C++ rules is still not finished at the moment, so the implementation for C++ rules is not fully done in starlark. We can try to

Using Bazel aspects to run clang-format

Bazel's aspects are next to rules the major building block used to extend the functionality of your build system. Contrary to rules, aspects allow to run particular functionality over an existing dependency graph. Aspect are documented pretty well on the bazel documentation page: Aspects | BazelBazel Let's build on top of

Creating a custom OpenEmbedded distro

All the code that you can read below, can be found under: https://github.com/ltekieli/custom-oe-distro OpenEmbedded, Yocto, bitbake confusion. I have to admit that Yocto and OpenEmbedded were always quite confusing in terms of what is what, especially looking at the history of both and the integration decisions

Cross compiling with Bazel

This time a short introduction to Bazel and how to cross-compile with this tool. I will explain how to build for host platform, as well as for multiple different targets. You can get the partial repositories used in this exercise here [https://github.com/ltekieli/bazel_cross_compile]. Installing Bazelisk

Using a custom GCC toolchain for embedded Linux development

So previously [/using-crosstool-ng-to-generate-a-gcc-toolchain/] I shortly introduced how to build a custom toolchain, now it's time to put it to use. A bare toolchain is rarely sufficient enough to build useful applications. We usually depend on external libraries, whether it's boost, protobuf or any other piece of code. This time, let's

Using crosstool-ng to generate a gcc toolchain

crosstool-ng [https://crosstool-ng.github.io/] is a handy tool for obtaining custom gcc toolchains which are tailored to your needs. This is especially useful when you are up to building a custom system for your embedded device, like a raspberry pi or a beagleboard. Building crosstool-ng itself crosstool-ng can be

Buildroot with Raspberry Pi - Automating and sharing

Automation is an important part of every software project. If you need to do something repeatedly, chances are, that it can be easily put in a script and done for you. It is especially important in build systems, that is why I would like to automate all the steps, that

Buildroot with Raspberry Pi - U-Boot

Raspberry Pi has a fairly complicated boot process with two bootloaders. The first one resides in built-in ROM and is responsible for starting the GPU. The GPU executes bootcode.bin, the second bootloader, which in the end runs the kernel. Although, there is a possibility to have the root file

Buildroot with Raspberry Pi - What, where and how to start

Recently, I started to dig into the topic of Linux kernel, especially from the embedded point of view. I got a chance to explore the operating system, its configuration and build process at Nokia, where I currently work. I decided to shift this exploration to a different kind of hardware.