Category: Brainwaves

Lately, I experimented with listening to podcasts on my PinePhone. The idea was to listen to some interesting topics while I’m on a walk, returning home. As you’d expect, nothing “just works” on a Linux phone.

I set up an automated download process via podget so that I can listen even with no network access. I got a pair of Bluetooth headphones to avoid fighting with headphone cords and to make this easy and convenient (as much as using a Linux phone can be). I picked up pragha as my new dedicated podcast player (‘P’ as in ‘Podcasts’!). The player even supported MPRIS2 via a plugin, so everything was great. Well, apart from my phone auto-suspending while the player was running.

One day later, I was halfway into creating a sleep-inhibit plugin for the pragha player. And then I found out there is an even better solution: sleep-inhibitor. This is a system service that monitors the audio output and if there is some sound playing through ALSA, it keeps the system from suspending. Just what I needed!

The service is even better than a player plugin, since this solution is generic. I also had a similar problem with the VLC player. And seeing this VLC ticket, I wasn’t the only one. Actually, this ticket brought me to the sleep-inhibitor, while researching ways to inhibit the system suspend.

Another way to print on a POS Printer on Linux is to use the python_escpos library. It requires programming, but if you really want to get a lower level access to the printer, this is a nice solution.

All you need is to connect the printer over USB, find out the vendor and product ID via lsusb, create a short python script using the escpos library and you can print text, images, barcodes, whatever!

This is the code I used for my Sewoo SLK-TS400 printer, identified as “0525:a700 Netchip Technology, Inc. POS PRINTER”:

from escpos.printer import Usb

p = Usb(0x0525, 0xa700)
p.text("Hello World\n")
p.barcode('1324354657687', 'EAN13', 64, 2, '', '')
p.cut()

Easy! Time to build a “Today’s News Headlines” service. Or maybe a “Error logs needing your attention” syslog service?

Wouldn’t it be nice to have a way to be woken up by your phone in the morning? Well, any old Android phone can do that! That was not the case with Linux phones. Until Birdie came along. Let’s consider the options:

Gnome Clocks? Nope. The app needs to be running for the alarm to activate.

Cron? Nope. When the phone gets suspended to save power, it will miss the alarm.

Wake Mobile? Close, but nope. It has most of the technology that is needed, but the alarm sound is annoying and it is not convenient to use. To be fair, this was only a proof of concept app. Some people reportedly used it anyway.

Birdie? YES! This one brings the minimum of features that I consider are required for an alarm clock.

Birdie features

• one recurring alarm for selected days
• ON/OFF switch
• pleasant alarm sound with gradually rising volume, starting from complete silence
• stop / snooze buttons
• configurable alarm sound
• wakes the system from sleep
• shows control buttons on the lock screen, without the need to log in

With this feature set, I can finally replace my Android phone as an alarm clock!

This week I found out about MPRIS: Media Player Remote Interfacing Specification. It is a standardized D-Bus interface for exposing metadata and controlls from a music player. Thanks to MPRIS, other apps can integrate such a music player seamlessly, e.g. onto the computer lockscreen.

What else can you do with MPRIS? Stop or Snooze your alarm clock! That’s right, the alarm clock Birdie designed for Linux phones (PinePhone) now acts as a music player. Now you don’t have to unlock the phone to stop an alarm in the morning!

I was looking for a convenient way of easily building AArch64 (ARM64 / ARMv8-A) packages for Arch Linux ARM, namely for the PinePhone. One option is to cross-compile the packages, but maintaining a cross-compilation toolchain is a pain. I wanted the experience of compiling natively without the need to heat up the weak ARM CPU these devices have.

QEMU to the rescue! It is possible to run an emulated Arch Linux ARM on a non-ARM device. This way you can compile natively. And with armutils this whole process of building packages can be automated. All you need is to install a few AUR packages, create an AArch64 chroot and start building!

Dependencies

You’ll need qemu-user-static-bin, binfmt-qemu-static-all-arch and finally armutils-git, installed from AUR (e.g. via yay).

Creating a chroot


mkarmroot -u http://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz <YOUR-PATH>/aarch64/root base-devel


Building a package

Assuming <YOUR-PATH>/pkg contains the package PKGBUILD file:

cd <YOUR-PATH>/pkg
sudo makearmpkg -r ../aarch64 -- --noconfirm


Done!

Don’t you love old video terminals? I know I do! That’s why I spent the few last weeks playing around with various terminal-related technologies: composite video, CRT monitors, old keyboards and the VT100 standard. The result is a working physical VT100 emulator, built around a CRT TV, LK201 terminal keyboard and an ESP32.

Source code, instructions and photos: video-terminal-revival repository

I obtained a vintage mechanical keyboard from 1988: Consul 262.9, made by Zbrojovka Brno. It features contactless Hall-effect switches (i.e. magnet sensors detect keypresses). It uses an XT protocol, so I had to create an adapter to make it usable for me. I could probably buy some cheap ready-made adapter, but where’s the fun in that?

Time to bring out the Arduino Leonardo! This newer Arduino features a HID-USB support, so it acts as a keyboard when connected over USB. All that remains is to connect the Arduino’s GPIOs to the keyboard’s pins and write a mapping layer between the “XT-keys” and “USB-keys”. Fun fact: this actually makes the keyboard programmable!

Here is the repository with the source code: xt-keyboard-adapter