I wasn’t able to find a tool to resize and center all open windows to a specific size for screen recording, so I came up with this AppleScript:

set windowWidth to 1024
set windowHeight to 768

tell application "Finder"
	set {0, 0, screenWidth, screenHeight} to bounds of window of desktop
end tell

tell application "System Events"
	set position of windows of (application processes whose visible is true) to {(screenWidth - windowWidth) / 2, (screenHeight - windowHeight) / 2}
	set size of windows of (application processes whose visible is true) to {windowWidth, windowHeight}
end tell

which you can save as an “Application” via Automator (built-in macOS app):

Save it to your desktop or any other convenient location. Double-click the app to run it.

Approve the permissions requests for Finder and System Events. In addition, open the “Settings” app and enable the newly created app under the “Accessibility” section:

This is an unedited video of me fixing a bug reported by a user on the WordPress support forum for my Widget Context plugin. Here is the pull request on GitHub if you want to follow along.

I start out by writing a unit test for the part of code that is responsible for the specific functionality and the new test actually fails so I’m able to find the bug and fix it while looking at related issues.

At the end I do the release dance — update the plugin version number, write the changelog, tag a release on GitHub and deploy to WP.org.

Let me know on Twitter or in the comments below if you would like to see more of this kind of content.

Here is a quick demo video of a bash script for updating the “Tested up to” version of multiple WordPress plugins at the same time. This solves the pain of updating the readme.txt file for all your plugins whenever a new version of WordPress is released.

p.s. Background music provided by my kids 🥁🥳🤣

Single channel LoRaWAN gateways are great for getting started with the LoRaWAN networks and actually sending some data from your sensors to the Things Network and other hubs. I built mine with HopeRF RFM95W radios attached directly to Raspberry Pi:

But single-channel gateways are not really useful to the larger LoRaWAN community because they listen only on one of the eight frequencies and can’t relay the majority of the LoRaWAN sensor traffic.

Eight channel gateways have always been around USD 200 until very recently when the following low cost gateways have been introduced:

• The Things Network Indoor gateway
• MicroTik wAP gateway
• RAK Wireless RAK7246

And only the RAK7246 gateway uses a DIY-friendly design with Raspberry Pi Zero as the brain of the device.

The Good

• Fully assembled device with all software pre-installed.
• DIY friendly design with Raspberry Pi Zero.
• Low price.

The Bad

• No labels for antenna and other ports.
• Impossible to remove the SD card without disassembling the case.

Buy the RAK7246 LoRaWAN Gateway

• Buy RAK7246 from the RAK Wireless Store.
• Buy RAK7246 from the RAK Wireless on Aliexpress.

Ikea Trådfri Zigbee switches/dimmers react much quicker to button presses compared to Xiaomi Mijia and Aqara switches because they don’t support double clicks. This is similar to how mobile browsers wait a little longer for clicks on links to support the long-press events such as copying the links or opening them in a new window.

Update: this project was featured in issue 92 of the official Raspberry Pi magazine (download as PDF, buy the issue or subscribe).

SSH-ing into a remote solar powered Raspberry Pi at the top of an apple tree has a special feeling — almost like commanding a spaceship where any mistake can cost you a lost link.

I build this project to remotely monitor our countryside house.

Internet Connectivity

There are two options:

1. A mobile USB modem attached directly to the Raspberry Pi using the point-to-point (PPP) protocol, or
2. A standalone mobile modem/router creating a WiFi network.

I decided to go with a standalone modem that is plugged in at my neighbours house because of complexities involved in creating a reliable PPP connection.

Components

• $8 Raspberry Pi Zero W which supports the camera module.
• $29 Raspberry Pi Camera module (and a cable for Raspberry Pi Zero).
• $18 any 12V battery capable of delivering 1.5W x 24h = 36Wh, such as this 7Ah Pb battery (80Wh).
• $8 dummy security camera.
• $10 12V charge controller.
• $2 12V to 5V buck converter to power the Raspberry Pi.
• $15 cabling and connectors.
• $132 100Wp solar panel.

Total: $222 + $7 per month for a 10GB mobile data plan.

Notes

• Avoid blocking the /dev/video0 device when not used to allow other things such as timelapse scripts to capture photos or record videos. This is hard with things like the Motion daemon which constantly blocks the video device source.
• Use the official picamera Python library for accessing the camera and formatting the image and video to match the required output.
• AutoSSH in combination with a custom systemd service is great for creating and maintaining a persistent SSH tunnel from Raspberry Pi to a remote server. Update: Use WireGuard for secure remote access.
• Rsync with hourly cron jobs is great for uploading and syncing photos and videos to a remote server for persistent storage. It also allows deleting older captures from Raspberry Pi while keeping them on the storage server.

Some of these scripts are available in this GitHub project repository.

Photos

The KEY-ID FIDO U2F security keys are a nice alternative to YubiKey 4 Nano because they cost only $12 instead of $50. However they include a green LED that is always enabled which makes it unsuitable for a permanent installation. In this video I explain how to open the device and remove the LED.

Here is a great overview of the most popular FIDO U2F security keys. And this blog post has useful technical insight into the Key-ID key.

In episode 9 of my video blog I explain the electronic components required for building a very simple and cheap electric skateboard with a hub motor. It is a follow-up to the part 1 of the DIY electric skateboard build video.

Components

• Maytech 70mm hub motor
• Maytech remote with a receiver
• 120A Car ESC
• 6S battery pack

In episode 8 of my video blog I show how to modify standard skateboard trucks to fit a 70mm electric hub motor from Maytech (available for $99). This is a follow-up to my review of the Maytech 90mm hub motors and part 1 in series of how to build your own light-weight electric skateboard.

Maytech 70mm Hub Motors

Here are the photos of the hub motor motor components — the stator, rotor and the wheel. The rest of the photos are available on Flickr.

To buy these motors you can get in touch with Eileen from Maytech eileen@maytech.cn — and don’t forget to refer to this blog for a discount.

FVT Sleeping Lion 120A Speed Controller (ESC)

During the first test run I was using the new high-voltage 12S 120A skateboard speed controller from FVT. Here are the photos of the teardown.

In episode 7 of my video blog I explain how I converted the popular Sony MDR-7506 headphones into wireless headphones using a bluetooth audio receiver from Havit. This is a follow-up video to my previous research in using Bluetooth audio for capturing microphone input on iPhone 7 which doesn’t have the 3.5mm audio input jack.

The Havit audio transceiver module uses the CSR8670 Bluetooth audio chip which is also used in most of the similar devices. It also features a very capable PAM8908 headphone driver and audio amplifier.

The 3.5mm input jack on the PCB can be soldered directly to the three audio signal wires of the Sony MDR-7508 headphones and placed inside the left headphone after drilling the required holes for the on/off switch, the micro-USB charging port and the 3.5mm audio input port which continues to work just like before the modifications:

After figuring out the GPIO pin names for the Orange Pi Zero expansion port it is relatively easy to configure any TFT display as a FBTFT device attached over the SPI bus, as long as you know the name of the chip used to drive the LCD screen. Here is a list of all the chips supported by the Linux kernel out of the box.

The display I have is very similar to this 3.2″ Waveshare touch-screen display (AliExpress / Amazon) that uses the ILI9340 LCD driver (PDF) chip. It was only a matter of specifying the two GPIO pins used for DC (Data or Command) and RST (Reset) in addition to the SPI port.

• H2+ port PA00 maps to GPIO 0, connected to RST
• H2+ port PA03 maps to GPIO 3, connected to DC
• H2+ SPI bus 1 is connected to the display module SPI pins.

The following command can be used to load the FBTFT device with the required configuration:

$ sudo modprobe fbtft_device custom name=fb_ili9340 gpios=dc:3,reset:0 speed=16000000 busnum=1 rotate=90

And then map the console output to the newly created framebuffer device:

$ con2fbmap 1 8

where 8 stands for /dev/fb8.

Here is the display running htop:

Permanent Setup

Create a new file /etc/modules-load.d/fbtft.conf with the following content:

fbtft_device

Create another file /etc/modprobe.d/fbtft.conf with the configuration for the fbtft_device device:

options fbtft_device custom name=fb_ili9340 gpios=dc:3,reset:0 speed=16000000 busnum=1 rotate=90

Finally, edit /boot/armbianEnv.txt to map the console output to the framebuffer device during the boot, by appending the following:

extraargs="fbcon=map:8"

In episode 5 of my video blog I review the PiJack Ethernet Hat ($15) for the Raspberry Pi Zero. This is a follow-up to my review of the Orange Pi Zero computer ($9) which has a built-in Ethernet and WiFi.

PiJack uses the Microchip ENC28J60 Ethernet controller which is capable of 10 Mbps (or just 1.25MB/s). While the Raspberry Pi Zero will recognize and configure the PiJack automatically, the actual networking speed didn’t exceed 5 Mbps with the iperf test or when downloading a large file over a local network using wget.

Here is the ethtool report with the PiJack connected:

Power Consumption

Transferring a 1GB file over a local network using PiJack attached to the Raspberry Pi Zero consumes around 170mA or 0.85W while the Orange Pi Zero uses around 100mA or 0.5W for the same task. These are only very rough figures and will probably be different with your setup.

Conclusions

PiJack is a good product if you don’t want to move away from the Raspberry Pi ecosystem for your project and you need to transfer only limited amounts of data. The Orange Pi Zero and NanoPi NEO are much cheaper at $10 and offer higher networking speeds and lower power consumption. The Armbian operating system has a great community and plenty people interested in improving both the performance and power consumption of these well documented Allwinner SoC based computers.

In episode 4 of my video blog I review Orange Pi Zero — the cheapest low-power computer with native Ethernet support, available on AliExpress for only $9. I’m using it as a headless webserver running Armbian to host a ToR relay. With Wi-Fi and USB ports disabled it consumes around 0.5W which amounts to 4.5kWh per year or $1.50.

In episode 3 of my video blog I showcase the Electric Poodle project — a motor on a stick that was supposed to pull you forward on a skateboard and roller skates. Unfortunately it didn’t work that well because it was too heavy and not very portable, and hard to use.

Here are a few similar projects that I discovered before and after building my prototype — E-Paddle, Speedbat and Kickstick.

In episode 2 of my video blog I review the Maytech 90mm sensored hub motor MTO9055HBM-60-HA for DIY electric skateboards and longboards. I compare it with the E-Wheelin i3 and show the trucks and the matching wheels.

Here are my rough notes on the various dimensions and parameters of the motor:

I’ve been wanting to do this since the days of Ze Show and Rocketboom so here we are on the first day of 2017. I knew that the first episode would be the hardest to make so I’m really looking forward to the next ones.

In the very first episode of my video blog I talk about batteries and USB battery packs, and how to compare their capacity ratings in mAh and Wh. Type 18650 battery cells are very popular for computer batteries, USB battery banks and electric cars including Tesla.

In the future episodes I’ll talk about my microcontroller projects, electric skateboards, scooters and bicycles, physical web, solar power, data logging and wireless transmission.