Categories
Brainwaves

Keeping PinePhone Awake With Podcasts

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.

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Categories
Brainwaves Linux

PinePhone Daily Cron Fixed

I needed to run a daily cron job on my PinePhone, but that turned out to be trickier than expected. How can you schedule a job to be run in the morning, when the phone is most likely asleep (suspended) at that time?

My solution (workaround?) was to have the cron job run every 10 minutes, checking if the job was already executed today and if not, run the actual job command. This check is pretty cheap and I don’t need to wake the phone up to run my job. All I need is to get the job executed “today, whenever you have the time”.

The Cron Limiter tool (crolim for short) is available in my snippets repository.

With this tool, the crontab is as easy as: */10 * * * * crolim podget. Now my daily podcasts can be downloaded daily, when the phone is awake.

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Categories
Brainwaves

PinePhone Printing Receipts (pt. 2)

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?

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Categories
Brainwaves Linux Open source

PinePhone Printing on a Thermal Receipt Printer

I like using PinePhone as a general purpose computer for various tasks and purposes, such as a dedicated alarm clock, trying out networking software (I have several of them), etc. This time I tried attaching a POS Printer, creating a print server.

Linux is great when it comes to printers support, thanks to CUPS. It usually just works. For the POS Printer I needed to install additional drivers, but luckily there are some generic ones available, covering most of the 58mm / 80mm thermal printers (they share the same ESC/POS protocol, making them widely compatible).

Initially I wanted to use the official vendor-supplied printer drivers for Linux ARM, but there are several ARM architectures and this wasn’t the right one. Therefore I used these CUPS drivers instead: github.com/klirichek/zj-58. And since this is open source, I was able to compile them for the PinePhone’s ARM architecture and get it working.

Adding a printer can be done through the CUPS web interface running on localhost:631, where you can add the printer connected over USB. You can also connect a printer over serial or Bluetooth, all you need is a special connection URL: serial:/dev/ttyXXX or bluetooth://123456789a/ where you specify the serial file or the device address.

Once the printer is added, you can use all the lp* commands to manage your print jobs, such as lpoptions to configure the printer defaults, or lp tux.png to print out an image on a thermal printer!

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Categories
Brainwaves Raspberry Pi

Kodi on Raspberry Pi 3 running Arch Linux ARM

When setting up Kodi under Arch Linux ARM running on Raspberry Pi 3, I encountered this error, which crashed the graphical environment right from the start:

[drm:vc4_bo_create [vc4]] ERROR Failed to allocate from CMA:
...

After some searching, I ran into an issue thread, where it was advised to increase the CMA memory (as a workaround that seems to just be the actual fix). You need to add ‘cma=256M’ to the kernel boot parameters. But how do you do that?

# Run as root...

# dependencies
pacman -S uboot-tools

# modify the kernel boot parameters
cd /boot
vim boot.txt # append cma=256M to the line with boot params
./mkscr
reboot

Before this fix, I had only 64 MB of CMA. This wasn’t enough. To check that this worked:

if the cma parameter is present and /proc/meminfo

cat /proc/cmdline
# should contain cma=256M

cat /proc/meminfo | grep Cma
# should say CmaTotal: 262144 kB

Now Kodi finally starts!

…though there are still some problems with the graphics driver (video doesn’t play, random switching to the console and back).

As it turns out, using the AArch64 version of Arch Linux ARM for Kodi is not the best option. Switching to the ARMv7 version helped a lot, everything worked from the start.

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Categories
Brainwaves

Birdie: Alarm App for Linux Phones

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!

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Categories
Brainwaves

What is MPRIS?

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!

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Categories
Brainwaves

Building AArch64 Arch Linux packages on a x86_64 host

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!

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Categories
Brainwaves

Video Terminal Revival

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

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Categories
Brainwaves

Zbrojovka Brno Consul 262.9 adapted to USB

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?

Consul 262.9 contactless keyboard, Zbrojovka Brno k.p.

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

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