Few days ago I had to create several systems from one raspbian image. While trying to change hostname for each, I ran into an issue
Fan control with dtoverlay on Raspberry
Another day working a bit for my SA818 radio node project. Today I tried active cooling with a 5V fan driven from RPIs 5V rail and controlled from GPIOs with a MOSFET (2N7002).
How to manage WordPress orphaned taxonomies
While developing my website I frequently got warnings. The one below means WordPress tried to access the property slug of an object that doesn’t exist (is null) and, as mentioned elsewhere, this usually happens when a menu, a snippet or other piece of code references a category that no longer exist.
Python: not enough values to unpack
While creating some code for the Arduino and C struct post, I ran into this issue “not enough values to unpack” and this has to do with Python’s struct format.
Arduino serial data transfer with C structs
While doing some tests with a 9-axis sensor I wnated to read all the values and send them all via an Arduino (or any other μ-controller) serial interface. You generate that data at point “A”, the sensor, and you want that data to arrive at point “B” with minimal delay, for example a computer software […]
Alternative to ssh-copy-id on windows
Lately I am doing a lot of development on Raspberry Pi systems and I use Visual Studio Code Remote Development. This is a neat feature because it allows me to connect from the same platform to multiple systems at once and work in parallel if I need. Visual Studio Code includes a full featured integrated […]
Using lsof
lsof command can show which processes are using which resources. This is extremely useful for troubleshooting. Basic syntax is: Without arguments, it lists all open files on the system (requires root privileges). Common Use Cases and Examples: Find which process is using a file: Find which process is using a port: The above command Lists […]
Attempt to read property “slug” on null
While developing my website I frequently got warnings. When WordPress tries to access the property slug of an object that doesn’t exist (is null), it throws the following (or similar) warning: This usually happens when a menu, a snippet or other piece of code references a category that no longer exist. This means somewhere in […]
Raspberry Pi serial interface issues
There is a problem I forgot to take care before creating the custom image for my radio node project. Programming SA818 module via Raspberry Pi’s UART interface cannot be done unless the UART interface is released from any interaction in console mode. I was banging my head for hours because of sustained DMOERROR message for […]
Cloning a Raspberry Pi SD card
Recently I had to make a bootable SD card for a Raspberry Pi Zero and I faced some issues. I thought to write some hints on how to properly clone and shrink a Pi image on an SD card. Here’s how you can create a compressed ISO (or disk image) from your Raspberry Pi SD […]
Add action button in WordPress code editor toolbar
Most of my website posts that include code use syntaxhighlighter to nicely format code. Unfortunately, you have to manually tag the piece of text as code. I thought it would be nice to have one or more buttons in the classical editor toolbar that will automatically surround the code with needed tags to be displayed […]
How to check the hardware version
Here are some handy commands that can be used to check the hardware version on a Linux-based machine.
Changing Quartus Prime project folder
I want to get back to FPGA design because I have some projects in mind and I did some in the past that were quite fun and very interesting. I am a bit rusty, though, and I am afraid I have to review all my past, and very diluted, experience with FPGAs. This has a […]
Why is journalctl -b -1 not working
Recently I hit a blocker when using journalctl -b -1 did not work. Using the flags ended up in error
NetworkManager connection priority
I recently ran into an issue with my Raspberry-based radio node. I tried to connect to some othet WiFi access points and I realized that I had no idea how to set connection priorities if I have multiple candidates for connection. I was used with wpa-supplicant way of doing things which was just to add […]
How to write to CM108 GPIO from Svxlink
CM108 has a set of four GPIOs that can be used via hidraw. These can be read from or write to.
I2S Raspberry Interface (4)
More work today. Some wires got loose and I did some experiments with .asoundrc and ALSA settings. I added a 39 Ω ballast resistor on SDIN and SDOUT lines and put a ferrite core on both wires. The radio node works as expected, absolutely no issues with one exception, a periodic pop that is audible […]
I2S Raspberry Interface (3)
Update July 11, 2025 Some thoughts and tasks today. The project is the same I2S interface.
Significant Svxlink power consumption
While testing my I2S project I ran into some boot issues on the Raspberry Pi 4 host. For what seemed to be some unknown reasons the boot process was completely chaotic, sometimes running well, sometimes hanging. I banged my head for some time looking for a solution until it came to my mind to change […]
I2S Raspberry Interface (2)
Update September, 2024. Activities and notes while developing the I2S interface for my radio node.
I2S interface for Raspberry Pi (1)
Today I managed to connect the Digilent Pmod I2S2 to a Raspberry Pi 4 and have all frequencies generated. This is part of an older project that I left abandoned for a while: a radio node built on Raspberry Pi and using Svxlink. As known, Raspberry boards do not have a proper audio interface and […]
How to embed script in wordpress footer
Another “tip of the day”. I ran into this while testing some carousels and swiping banners. All needed the associated js scripts to be loaded lastly after the main page/ post content was already available. It seems that using wp_enqueue_script last argument as true will do the trick: Hope you will find this useful. Cheers […]
Why CSS margins collapse
While working on my new theme for this site I ran into a problem: CSS collapsing margins. Well, from the beginning let me be very clear: this will not be a comprehensive article on this subject. There is already one written by Josh Comeau and is excellent: “The Rules of Margin Collapse“. I urge you […]
Genetic algorithm mutation coded in Python
This example is adapted from Clinton Sheppard’s excellent book “Genetic Algorithms with Python“, a book that I encourage you to buy and read. The very simple example shows how easy is to design in Python a simple mutation algorithm that merges to the optimal solution in 24 iterations. The example below uses romanian language accents […]
KiCAD, Python and PyCharm
I am not a huge fan of KiCad. However, given the limited and abysmal options that we have for free EDA packages, KiCad is quite ok, although terribly flawed in some areas. Maybe the development team should focus on some simple functionalities like support for rounded traces, net group routing, zones, a simple way to […]
Quartus files
One of the biggest issues that I have, in general, while learning different stuff is lack of properly-explained abbreviations. I am starting today a compilation of Altera/ Intel Quartus list of filenames and abbreviations. Source: Intel/ Altera Glossary .qws – Quartus Workspace File. The Quartus® Workspace File (.qws) is a non-editable file that stores user […]
How to install Python 3.7 on Raspberry Pi
This short guide explains how to install Python version 3.7.0 on a Raspberry Pi running Raspbian. First, get rid of old versions: Ensure system is up to date: Install the dependencies needed for building the distribution: build-essential tk-dev libncurses5-dev libncursesw5-dev libreadline6-dev libdb5.3-dev libgdbm-dev libsqlite3-dev libssl-dev libbz2-dev libexpat1-dev liblzma-dev zlib1g-dev libffi-dev Get the python src distribution: […]
Error opening serial port
Encouraged by the latest developments, today I started building a new application that will allow remote connection to Kenwood TH-D74, remote control and APRS data transfer. However, while building and running the app I got the following error: If you encounter this, be aware that it is generated by application sandboxing. You can think of using […]
TH-D74 BLE or “Bluetooth Low Energy”
Struggling to understand how Universal Unique IDs work (see here) I was wrongly assuming that Core Bluetooth is a framework from Apple that covers all aspects of communication with devices via BT. I was WRONG ! scanForPeripheralsWithServices method and, in general, what I tried to do, for almost a week, is NOT good for my intended […]
Using UUIDs and Bluetooth
I did some more steps towards accessing Kenwood TH-D74’s services via bluetooth. I struggled for some time understanding how discovery based on UUIDs work. I was not aware that, for each service profile, there is a standard Universally Unique Identifier (UUID) documented in Bluetooth SIG specs. Specifically for Serial Port Profile (SPP) service, the UUID […]