Other

Running Raspbian in image on Ubuntu desktop

While the title says Raspbian on Ubuntu, the steps will be nearly the same for any ARM linux distribution on any AMD64 Linux desktop. For me, and I suspect most people, what combination is likely to equal Raspbian on Ubuntu.

Download and extract your Raspbian image. In this case I will be using Raspbian Lite and this is the filename of the image: 2019-04-08-raspbian-stretch.img

First, setup: sudo apt install qemu binfmt-support qemu-user-static systemd-container

After the setup, run the following steps every time you want to run a Raspbian image on Ubuntu.

sudo kpartx -v -a ./2019-04-08-raspbian-stretch.img

That will print something like:

add map loop11p1 (253:0): 0 89698 linear 7:11 8192
add map loop11p2 (253:1): 0 8392704 linear 7:11 98304

The first line is the raspbian boot partition, the second will be the rootfs partition.

udisksctl mount -b /dev/mapper/loop11p2

After the prior command, a rootfs mount should appear in /media/<your_username>/. You can copy files into either and they will be placed into the image file you mounted.

sudo systemd-nspawn -D /media/<your_username>/rootfs/

Ctrl-D to exit.

udisksctl unmount -b /dev/mapper/loop11p2

sudo kpartx -d ./2019-04-08-raspbian-stretch.img

Note, a more advanced use might be to copy some sort of initialization script into the image after mounting the image and before running systemd-nspawn. Then, invoke that command something like: sudo systemd-nspawn -D /media/<your_username>/rootfs/ /bin/bash /home/pi/your_script.sh

Other

Dynamic Wireless Network Name (SSID) on Raspberry Pi hotspot

This mostly for any Linux system using systemd, albeit the make_ssid.sh script will need adjusted for where you want to get the ID from. In the example, it uses the Raspberry Pi’s serial number. Mac address could be another good source to use.

make_ssid.sh goes in /etc/hostapd/
The service file goes in /etc/systemd/system/
view raw README hosted with ❤ by GitHub
[Unit]
Description=Setup ssid to use for hostapd
Before=hostapd.service
[Service]
Type=oneshot
ExecStart=/bin/bash /etc/hostapd/make_ssid.sh
StandardOutput=journal+console
[Install]
WantedBy=multi-user.target
view raw hostapd_set_ssid.service hosted with ❤ by GitHub
#!/bin/bash
set -e
egrep -v "^ssid" /etc/hostapd/hostapd.conf > /tmp/hostapd.new
grep Serial /proc/cpuinfo | awk '{ print "ssid=example_ssid_" $3 }' >> /tmp/hostapd.new
mv /tmp/hostapd.new /etc/hostapd/hostapd.conf
view raw make_ssid.sh hosted with ❤ by GitHub

Other

Kivy on Raspbian using EGL without installing X11

This is aimed more at using the Raspberry Pi with a touch screen for embedded uses, and is not relevant to using it in the Raspbian desktop environment.

Unfortunately, it seems that to just pip install kivy appears to work, but then when you run an example, it complains about missing libraries, and installing those eventually gets you to the point where you need X11 because of the dpkg dependencies being overly broad.

If you build Kivy from source you can avoid that.

apt install python-pip python3-pip gir1.2-glib-2.0 libdbus-glib-1-2 libexpat1-dev libgirepository-1.0-1 \
   libpython3-dev libpython3.5-dev python-pip-whl python3-cffi-backend \
   python3-crypto python3-cryptography python3-dbus python3-dev python3-gi \
   python3-idna python3-keyring python3-keyrings.alt python3-pyasn1 \
   python3-secretstorage python3-setuptools python3-wheel python3-xdg \
   python3.5-dev evtest libmtdev-dev zlib1g-dev libfreetype6-dev liblcms1-dev \
   libopenjp2-7 libtiff5 libjpeg62-turbo-dev git git-man liberror-perl

pip install virtualenv

git clone https://github.com/kivy/kivy

virtualenv -p /usr/bin/python3 kivy_build

source kivy_build/bin/activate

pip install cython pillow

#cd kivy
#USE_SDL2=0 CFLAGS="-I/opt/vc/include/" make
USE_SDL2=0 CFLAGS="-I/opt/vc/include/" pip install ./kivy/

Other

Substance Designer SBSPRS/SBSAR file format notes

I have never used Substance Designer, so I’m basing this off of looking at example files.

The SBSPRS files are XML that appear to specify the list and type of parameters used in the SBSAR substance.

The SBSAR file is just a 7-zip file. It expands to:
./assemblies
./assemblies/content
./assemblies/content/0000
./assemblies/content/0000/icon1234567890.png
./assemblies/content/0000/Example.xml
./assemblies/content/0000/Example.sbsasm

The Example.xml file appears to describe the inputs of the node, the outputs of the node, gui layout for the node, and presets to choose for the node.

The Example.sbsasm file starts with the magic word 5342 414d, which are the ASCII values for SBAM. Beyond that, I haven’t figured anything else out about it.

I was hoping that this would be compressed formats, XML, JSON, and/or IFF all the way down.

Other
Aside

In case anyone is interested in making USB connectors a bit more kid proof, I recently bought these magnetic USB cables: https://www.amazon.com/gp/product/B074TB8XTL
For the kid’s tablet, I super glue the micro-usb adapter in place. It sticks out about 1/8 in. No more kid destroying USB ports.
It’s like Apples MagSafe for tablets.
For their claim that it will prevent “tripping over cable resulting in smashed phones”, the magnetic pull is strong enough to yank at least some phones off a table when the cord is accidentally pulled (say by tripping on it).

Reviews

Logitech K780 and M720 mini review

I rather like the K780 keyboard and M720 mouse from Logitech (alas, not sold as combo). Just picked it up a week ago, so I can’t say about longevity yet, but they feel solid. The key shape on the keyboard is odd, but I’m already used to it from a K380 elsewhere.

I had 2 wireless keyboards and mice. One of each plugged into my KVM and one of each plugged into my windows PC on a separate monitor. Both of the K780 and M720 support connecting to 3 machines. Those three connections can be via Logitech’s unifying receiver (what you get in all cheap Logitech wireless mice) or bluetooth. Each device came with one receiver, and their software will let you re-pair their devices (unlike other brands of cheap USB wireless, I’m looking at you Anker). Thus, I stuck one receiver into the KVM, one into the windows PC, and re-paired both devices to talk to both receivers so now I have one keyboard and one mouse and I can easily toggle them between 3 computers (while still having an open slot on both devices for a tablet, Raspberry Pi, or something else).

Acurately predicted 20 out of the last 4 Zebra stampedes.