I2C is a simple open-drain bus that is popular for connecting devices to microcontrollers (MCUs), such as sensors, RTCs, displays etc. Devices on the I2C bus are addressed by 7 bits and the bus data and clock lines are pulled-up by a set of pull-up resistors. A good first test …
This article describes how to measure a pulse-width-modulated (PWM) signal using the Pokit Meter device.
The Pokit Meter is a very small digital multimeter (DMM) like device that can be interfaced over Bluetooth Low Energy (BLE). Due to its design and small form factor it comes with many limitations, but …
The GD32VF103 is an inexpensive 32 bit RISC-V CPU that integrates a bunch of peripherals. In other words, it's a cheap RISC-V microcontroller (MCU). This article describes how to hook it up, to set up an development environment and do some first steps with its peripherals.
It's well known that syscalls are expensive. And that software mitigations against CPU bugs (such as Meltdown) even have made them more expensive. But how expensive are they really? To begin to answer this question I wrote a small micro-benchmark in order to measure the minimal costs of a syscall …
More and more open source projects seem to switch to the Meson build tool, in the last years. In an attempt to quantify this development I looked at the build tools usage by Fedora packages, during the last 14 years.
Meson is a build tool with good C …
The beauty of perfect hashing is that you never have to deal with any collisions during item lookup. I recently created libphashtable, a perfect hashing hash table library for C/C++ which focuses on minimizing item lookup latency jitter. This article presents benchmarking results that show how its lookup times …
Deploying a new virtual machine 'in the cloud' is simple enough and fast. As long as one doesn't need to setup an encrypted root filesystem. This article shows how to automate the setup of a Fedora system with an encrypted root filesystem remotely - 'in the cloud' - on e.g. a …
When deploying a VM in a remote location one might end up in an impossible situation: a VM base image doesn't contain SSH host keys as otherwise the image couldn't be shared between multiple hosts. But if SSH host keys are auto-generated during the first boot one doesn't know their …
Perhaps the most interesting part of the open RISC-V instruction set architecture (ISA) is the vector extension (RISC-V "V"). In contrast to the average single-instruction multipe-data (SIMD) instruction set, RISC-V vector instructions are vector length agnostic (VLA). Thus, a RISC-V "V" CPU is flexible in choosing a vector register size …
Recently, I launched MANPATH.be - a site for convenient man page browsing. It provides access to the man pages of different distributions, including Fedora, CentOS and OpenSolaris. The about page concisely describes some of the sites features, e.g. human readable links like f30/3/memcpy, permalinks and various kinds …