Thank you to M Khanfar for submitting his video that shows a step-by-step tutorial on building your own SSB receiver in Windows GNU Radio for QO-100 satellite reception.  His tutorial includes adding several tuning sliders in the GNU Radio GUI as well.

QO-100 / Es'hail-2 is a geostationary satellite at at 25.5°E (covering Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia) providing broadcasting services. However, as a bonus it has allowed amateur radio operators to use a spare transponder. Uplink is at 2.4 GHz and downlink is at 10.5 GHz. We note that we are selling a "bullseye" LNB in our store which allows most SDR dongles to be able to receive the signal with high frequency accuracy.

The Bullseye LNB that we have in our store is great for receiving the QO-100 amateur geostationary radio satellite which is available in some parts of the world. However it cannot be used to transmit to the satellite. Over on his YouTube channel Tech Minds shows us how to build a transmit helix antenna that connects to the Bullseye or other suitable LNB, resulting in a dual feed antenna.

The antenna that was built is based on DO8PAT's "Ice Cone Feed" design. The design requires some 3D printed parts for the mount and housing, as well as a copper wire helix, metal reflector and copper matching strip. The Bullseye fits onto the back of the helix mount. Once mounted on a dish Tech Minds shows that he was able to make contact with a friend via the QO-100 satellite with good signal strength.

Thank you to John D for writing in and letting us know that Wired magazine has recently run an article about the "Nyansat" project. Nyansat aims to bring low cost open source satellite ground stations to the masses. The goal is to democratize citizen access to space by allowing for easier collection of satellite data, or even for collaborative citizen science radio astronomy projects such as the detection of space debris or undocumented satellites. John writes:

While most people think of a satellite ground station as a giant dish mounted on top of a building in the desert, technically any radio receiver that tunes into a satellite's signal can be called a ground station.  Somewhere between the giant dish and the GPS chip in your phone is a ground station that uses a directional antenna to pull in the faint signals.  So unless you're only interested in geosynchronous satellites, the antenna needs to be aimed at the satellite, and that's where NyanSat comes in. 

The design of the NyanSat consists of a pan-tilt head, an Inertial Measurement Unit (IMU) for precise azimuth and elevation measurements, a motor-driver board, an optional OLED display, an optional GPS module, and is powered by an ESP32.  Full source code is available in their git repo, found at https://github.com/RedBalloonShenanigans/antenny. The NyanSat's software is written in micropython specifically for the ESP32, but obviously could be ported if desired.

Mounting an antenna, adding an RTL-SDR, and actually tuning in a satellite, is still up to the builder.

One of the goals of the NyanSat project is to eventually build up a network of ground stations that can collaborate to contribute frequently updated satellite ephemeris information.

When they're in stock, the project's sponsor, Red Balloon Security, has occasionally been offering a kit containing a custom PCB that is pre-populated with the ESP32 and motor driver; a pan-tilt gimbal; an IMU; and an RTL-SDR.  They've been selling them for $1.00(!), just to get them out in the hands of people.  Keep your eye open in case they get another batch in.

The Red Balloon store lists the kit as currently out of stock so we suggest keeping an eye on their store just in case any of the $1 kits come back in stock.

NyanSat will also present a live twitch demo at this years online DefCon conference on Friday Aug 7 6:30-8PM EDT and Sat Aug 8 6:30-8PM EDT. On Sun Aug 9 12:30 EDT they will hold another event where they judge the best work of the Nyansat community.

The SatNOGS project which we have covered many times before on this blog is quite similar with it's own open source antenna rotator design, however the Nyansat design looks a bit easier to build as it doesn't require 3D printed parts. Although critically from their demos we haven't seen what sort of sized antennas the gimbal chosen by Nyansat is capable of moving.

DEFCON 2020 was held online this year in and the talks were released a few days ago on their website and on YouTube. If you weren't already aware Defcon is a major yearly conference all about information security, and some of the talks deal with wireless and SDR topics. We found two very interesting SDR and wireless related talks that we have highlighted below. The first talk investigates using commercial satellite TV receivers to eavesdrop on satellite internet communications. The second discusses using a bladeRF or USRP to detect fake 4G cellphone basestations. Slides for these talks are available on the Defcon Media server under the presentations folder.

DEF CON Safe Mode - James Pavur - Whispers Among the Stars

Space is changing. The number of satellites in orbit will increase from around 2,000 today to more than 15,000 by 2030. This briefing provides a practical look at the considerations an attacker may take when targeting satellite broadband communications networks. Using $300 of widely available home television equipment I show that it is possible to intercept deeply sensitive data transmitted on satellite links by some of the world's largest organizations.

The talk follows a series of case studies looking at satellite communications affecting three domains: air, land, and sea. From home satellite broadband customers, to wind farms, to oil tankers and aircraft, I show how satellite eavesdroppers can threaten privacy and communications security. Beyond eavesdropping, I also discuss how, under certain conditions, this inexpensive hardware can be used to hijack active sessions over the satellite link.

The talk concludes by presenting new open source tools we have developed to help researchers seeking to improve satellite communications security and individual satellite customers looking to encrypt their traffic.

The talk assumes no background in satellite communications or cryptography but will be most interesting to researchers interested in tackling further unsolved security challenges in outer space.

DEF CON Safe Mode - Cooper Quintin - Detecting Fake 4G Base Stations in Real Time

4G based IMSI catchers such as the Hailstorm are becoming more popular with governments and law enforcement around the world, as well as spies, and even criminals. Until now IMSI catcher detection has focused on 2G IMSI catchers such as the Stingray which are quickly falling out of favor.

In this talk we will tell you how 4G IMSI Catchers might work to the best of our knowledge, and what they can and can't do. We demonstrate a brand new software project to detect fake 4G base stations, with open source software and relatively cheap hardware. And finally we will present a comprehensive plan to dramatically limit the capabilities of IMSI catchers (with the long term goal of making them useless once and for all).

GitHub: https://github.com/EFForg/crocodilehunter

With an RTL-SDR, an appropriate satellite antenna and LNA it is possible to receive visible light images from geostationary satellites such as GOES/Himawari and GK-2A. However, in a 24 hour cycle there will only be one or two images that show the Earth fully illuminated by the sun. The rest of the day parts or all of the Earth will be dark with not even clouds visible. To get around this the satellites also use an Infrared (IR) camera which can see clouds at all times. However, these images are greyscale and not very visually appealing.

To fix this aesthetic issue there is now a recently released multiplatform tool called "Sanchez" which will combine a high resolution underlay image with the greyscale IR image in order to create a more beautiful image. The software is command line based and can run on a batch of collected images.

Over on his YouTube channel Tech Minds has uploaded a video showing how it's possible to receive and decode GPS signals with an RTL-SDR. To do this he uses one of our RTL-SDR Blog V3 dongles and a GPS patch antenna which is powered via the bias tee on the dongle.

On the software side he uses GNSS-SDRLIB and RTKLIB to decode the GPS signal. The result of the two programs is your current GPS coordinates which can be plotted on a map. Unfortunately in the video Tech Minds was unable to get the Google Maps display to work, but you can easily type the coordinates into Google maps yourself.

Back in May we started selling the Bullseye LNB on our store, which is an ultra stable LNB for receiving QO-100 and other Ku-Band satellites/applications. We have recently managed to secure a good deal from the supplier. However, our storage warehouse is now low on space and we are hence running a 33% off stock clearance sale with the unit now priced at only US$19.97 including free worldwide shipping to most countries. 

To order the product, please go to our store, and scroll down until you see the QO-100 Bullseye TCXO LNB heading. Alternatively we also have stock via our Aliexpress store or on eBay.

What is QO-100 and an LNB?

QO-100 / Es'hail-2 is a geostationary satellite at at 25.5°E (covering Africa, Europe, the Middle East, India, eastern Brazil and the west half of Russia/Asia) providing broadcasting services. However, as a bonus it also has the world's first amateur radio repeater in geostationary orbit. Uplink is at 2.4 GHz and downlink is at 10.5 GHz.

Most SDRs do not tune all the way up to 10.5 GHz, so an LNB (low noise block) is typically used, which contains the feed, an LNA, and a downconverter which converts the 10.5 GHz frequency into a much lower one that can be received by most SDRs.

What's special about the Bullseye LNB?

In order to properly monitor signals on QO-100 an LNB with a Temperature Compensated Oscillator (TCXO) or other stabilization method is required. Most LNBs have non-stabilized crystals which will drift significantly over time on the order of 300 PPM with temperature changes.  This means that the narrowband signals used on QO-100 can easily drift out of the receive band or cause distorted reception. Software drift compensation can be used to an extent, but it works best if the LNB is somewhat stable in the first place. It is possible to hand modify a standard Ku-band LNB by soldering on a replacement TCXO or hacking in connections to a GPSDO, but the Bullseye LNB ready to use with a built in 1PPM TCXO and is cheap.

Reviews

In the past Tech Minds has reviewed this product favourably in the video shown below. In a second video he has also shown how the Bullseye can be combined with a transmit helix in order to create a dual feed uplink + downlink capable antenna.

F4DAV has also reviewed the unit on his website, concluding with the following statement:

As far as I know the BE01 is the first affordable mass-produced Ku-band TCXO LNB. These early tests suggest that it can be a game changer for amateur radio and other narrowband applications in the 10 GHz band. The stability and ability to recalibrate should allow even unsophisticated analog stations to tune to a 5 kHz channel and remain there for hours at a time. For SDR stations with beacon-based frequency correction, the absolute accuracy removes the need to oversample by several hundred kHz or to scan for the initial frequency offset.

There are also several posts on Twitter by customers noting good performance

Official Feature List + Specs

Features

• Bullseye 10 kHz BE01
• Universal single output LNB
• Frequency stability within 10 kHz in normal outdoor environment
• Phase locked loop with 2 PPM TCXO
• Factory calibration within 1 kHz utilizing GPS-locked spectrum analyzers
• Ultra high precision PLL employing proprietary frequency control system (patent pending)
• Digitally controlled carrier offset with optional programmer
• 25 MHz output reference available on secondary F-connector (red)

Specifications 

• Input frequency: 10489 - 12750 MHz
• LO frequency 9750/10600 MHz
• LO frequency stability at 23C: +/- 10 kHz
• LO frequency stability -20 - 60C: +/- 30 kHz
• Gain: 50 - 66 dB
• Output frequency: 739 - 1950 MHz (low band) and 1100 - 2150 (high band)
• Return loss of 8 dB (739 - 1950 MHz) and 10 dB (1100 - 2150 MHz)
• Noise figure: 0.5 dB

We note that an external bias tee power injector is required to power the LNB as it requires 11.5V - 14V to operate in vertical polarization and 16V - 19V to operate with horizontal polarization. The bias tee on the RTL-SDR Blog V3 outputs 4.5V so it is not suitable.

Elektro-L is a range of Russian geostationary weather satellites. Elektro-L1 and L2 were launched in 2011 and 2015 respectively, and Elektro-L3 was launched more recently in December 2019. Currently only Elektro-L2 and L3 are in operation. Like it's NOAA GOES, Himawari and GK-2A cousins, Elektro-L satellites beam back full disk images of the entire earth.  Elektro-L2 is positioned to cover South America, Africa and Europe, whilst Elektro-L3 covers the East of Africa, Eastern Europe, Russia, Middle East, Asia and the West of Australia.

Recently @aang254 has been Tweeting that he has managed to get an Elektro-L decoder working. The decoder is open source and available on GitHub and Windows builds are already available. He notes that he's still working on the demodulator, but that should be released tomorrow. This decoder is great news as now Europeans now have an opportunity to receive full disk images. There is no full guide yet on how to use the decoder, but we expect that one will be released soon.

We note that according to wmo-sat.info the Elektro-L satellites transmit at ~1693 MHz, and have a 2 MHz wide HRIT and 200 kHz wide LRIT mode. So the signals should be able to be received with an RTL-SDR and appropriate LNA. EDIT: Unfortunately it seems that wmo-sat.info may have incorrect information, and that Elektro-L requires X-Band hardware to receive these images. While not totally impossible, an X-Band satellite SDR setup is a bit more difficult to put together compared to the L-band SDR setup used by GOES and GK-2A.

Back in August we posted about the release of Sanchez, a tool originally designed to apply a color underlay image to grayscale infrared images received from geostationary weather satellites such as GOES 16/17, Himawari-8 and GK-2K. The tool has recently been updated with some very nice new features.

One of the new features is the ability to composite together images obtained from multiple satellites in order to form a full equirectangular image of the earth with live cloud cover. Another feature is the ability to use two or more images from different satellites to reproject back to geostationary projection at a specified longitude, essentially creating an image from a virtual satellite.

Back in June we posted about the release of  Zbigniew Sztanga's NOAA-HIRS-Decoder which can decode HIRS instrument data which measures the vertical temperature profile of the Earth's surface. This HIRS signal is broadcast by NOAA satellites at the same time as their APT images and the HIRS frequency is close by at 137.350 MHz. 

Recently Zbigniew has released a new decoder for the Microwave Humidity Sounder (MHS) instrument which is available on NOAA-19 only. This MHS instrument observes the Earth in the 89-190 GHz microwave band, which can be useful for measuring humidity levels. However, unlike the APT and HIRS signals which downlink data at around 137 MHz, the MHS data is broadcast in the L-band within the HRPT signal, so a motorized or tracked satellite dish will be required to receive it. Zbigniew writes:

The MHS (Microwave humidity sounder) is an instrument on NOAA-18 and NOAA-19. It replaced the older AMSU-B. It has a resolution of 90px per line and 5 channels.

 

Data from the instrument is present in HRPT and can be decoded with my new software. Unfortunately, only MHS on N-19 is working, because N-18's NHS is dead.

 

The instrument can be used to monitor low clouds, percipation and water vaopr in the atmosphere. I attached a sample image to the email.

 

It's available on the same repo as Aang23' HRPT decoders: https://github.com/altillimity/L-Band-Decoders/tree/master/NOAA%20MHS%20Decoder

On September 15 we began our 33% off stock reduction sale for the Bullseye LNB. The Bullseye is an ultra stable LNB for receiving QO-100 and other Ku-Band satellites/applications. We'll be ending this sale on Wednesday, so if you'd like to purchase a unit please order soon to avoid missing out on the sale price. The current sale price is US$19.97 including free worldwide shipping to most countries. 

To order the product, please go to our store, and scroll down until you see the QO-100 Bullseye TCXO LNB heading. Alternatively we also have stock via our Aliexpress store or on eBay.

For more information about the Bullseye and some reviews please see the original sale post.

Recently we posted about new updates to the Sanchez software. The updates allow users to combine images received from multiple geostationary weather satellites such as GOES 16/17, Himawari-8, GK-2A and Electro. The images can also be reprojected into a flat equirectangular image, and then optionally reprojected back into a disk view at any location on earth. Sanchez's original function is also still there which allows users to add a false color underlay image to grayscale infrared images received from the satellites.

Sanchez is a command line tool, so scripts are required to do anything interesting. Over on his page Carl Reinemann has uploaded a page with a number of Sanchez command line examples available. The page shows examples like how to stitch together multiple images, and how to create a stitched time lapse animation. The YouTube video below shows an example of an animation Carl created with Sanchez and GOES 16 and 17 images stitched together.

And the image below is an example of an image of Himawari 8, GOES 16 and 17 he stitched together with Sanchez.

NooElec have recently released for sale a GOES geostationary weather satellite reception bundle which includes a parabolic grid dish, feed, GOES LNA and RTL-SDR dongle. The bundle should be usable for the GK-2A satellite, as well as HRIT from polar orbiting satellites, although for HRIT those you'll need some way to motorize or hand track the satellites.

Typically to receive GOES a 2.4 GHz WiFi grid dish has been used in the past. While the mismatch between 2.4 GHz and the 1.7 GHz used by GOES doesn't cause too much trouble, the dish provided by NooElec has a feed optimized for the 1.7 GHz which should make receiving the signal easier. The bundle also comes with their SAWbird+ GOES LNA, one of their always ON bias tee E4000 tuner based RTL-SDR dongles and a roll of 10m LMR400 cable.

The bundle is currently available on Amazon USA priced at US$179.95. Canadian customers can also order from Amazon.ca for CDN$259.95. Amazon shipping is free within the USA, however shipping this overseas will cost at least US$100 extra due to the weight + additional import fees. That said, the coverage area of GOES is mostly only for the USA, Canada and South America.

If you're interested in GOES or GK-2A satellite reception we have a tutorial written here.

For some time now many weather satellite enthusiasts have enjoyed the ability to relatively easily receive live high resolution images directly from the GOES-16, GOES-17 and GK-2A geostationary satellites (tutorial here). However, while much of the world can see at least one of these satellites, European's have been left out.

What may be of some interest to Europeans is that the older GOES-13 (aka EWS-G1) satellite was repositioned in February 2020, and it can now be received in Europe (as well as Africa, the Middle East, Asia, Russia and West Australia) until at least 2024 when it will be replaced.

The important catch however is that GOES-13 is not broadcasting the same easy to receive LRIT/HRIT signals that the other satellites use. The signal is still in the L-Band at 1685.7 MHz, however it is called "GVAR" and it is much weaker and uses 5 MHz of bandwidth. For GOES 16/17 and GK-2A a 1m WiFi grid dish, LNA and RTL-SDR was sufficient, but for GOES-13 you'll need a much larger 1.8m dish, and a wider band SDR like an Airspy. The big dish requirement significantly increases the reception challenge.

We also note that the decoder is being developed by @aang254 and u/Xerbot and it is not yet publicly released. However, they do intend to release it soon.

Over on his blog Carl Reinemann has been collecting some useful information about GOES-13 reception. Over on Reddit u/derekcz has also created a post with some useful information. We've also been talking to @ZSztanga in Poland who has been testing this satellite out, he wrote:

My hardware is: 180cm prime focus dish, with a custom cantenna (120mm diameter). I'm using the SAWBIRD GOES LNA. I will be switching to the + version, because the setup is still lacking a few db SNR. The SDR is the one I use for HRPT: the airspy mini

I found that the USB connection on the airspy generates a lot of noise, so I removed the USB cable, by moving the airspy to the laptop. I use 2m of CNT-400 coax and it works much better now. I get about 2 db SNR more. Thought you might find it interesting.

We note that there is some interesting differences with GOES-13 images. Since the image is less processed, it is higher resolution (a full resolution image can be found on this Reddit post), as well as not cropped, meaning that the Earth's atmosphere is visible. Please also follow @ZSztang on Twitter for more images.

Hot on the heels of the GOES-13 weather satellite decoder that we posted about a few days ago, @aang254 has just released a new RTL-SDR compatible decoder for the FengYun-2H, 2G and possibly 2E geostationary weather satellites.

The FengYun-2 line of weather satellites are the Chinese equivalents to GOES, and they are positioned to cover parts of Europe, Africa, the Middle East, Asia, Russia, and Australia. So this is another geostationary weather satellite now available to Europeans which broadcasts in the L-Band at 1687.5 MHz. And unlike the weaker GOES-13 L-Band downlink, the FengYun-2 downlink is much stronger which means that reception with a 120cm satellite dish should be possible. We note that it has not yet been confirmed if the typical 90-100 cm WiFi dishes used with GOES-16 and 17 will be big enough to work. @aang254 writes:

Yesterday I successfully decoded the S-VISSR downlink from FengYun-2H thanks to a recording by @MartanBlaho. It is stronger than PDR on EWS-G1 (see Zbychu's signal https://twitter.com/ZSztanga/status/1329801728162754560…) meaning it should (untested) be doable with a 120cm (or smaller but no confirmation again) dish instead of 180cm.

It covers parts of Europe, Russia and down to Australia. FY-2G and FY-2E (no confirmation for this one yet) are also decodable in the same way. I released an early decoder, that currently is not suitable for automated setups but allows getting images already. A later version (that should come soon-ish) will allow live decoding / autonomous setups in a similar fashion to other satellites.

Also, the res is 2km/px on VIS and 8km/px on IR, so half that of GOES-13 with similar-ish coverage (Europe is less visible though).

(also forgot to say but the bandwidth is under 2Mhz, allowing a rtlsdr to be used)

https://github.com/altillimity/S-VISSR-Ingestor

Over on his YouTube channel TechMinds has uploaded a new video showing how to decode signals from Orbcomm satellites. Orbcomm run a global network of low earth orbit satellites that perform services such as Internet of Things (IoT), Machine 2 Machine (M2M) communications, asset tracking, utilities telemetry, government communications and much more. The signals can be received at around 137 MHz.

In the video he explains how the private client data is encrypted, however it is possible to at least see the encrypted data coming down, and decode some of the data management information such as the transmitted uplink frequencies using a program called Orbcomm Plotter. Ultimately, the data available is quite boring to monitor, however decoding these satellites is still an interesting exercise.

Thank you to Derek @ok9sgc for pointing us to some work Reddit user u/Xerbot has been doing on receiving telemetry coming down from a "dead" 1960's satellite called Transit-5B5. The fleet of Transit satellites was used for military navigation with the first launch in 1959 and the last in 1988. All in the fleet have since died apart from Transit-5B5 which continues to transmit telemetry at 137 MHz when receiving power from in the sun. Derek writes:

Turns out that the TRANSIT 5B-5 satellite's telemetry still has signs of some of the satellite's systems operating (albeit with a questionable reliability). The satellite represents an amazing legacy for all the people that worked on it in the 1950s and 60s, but due to its age it is also very difficult to find technical documentation about the telemetry (or I should rather say impossible), so to make sense of the data that's being broadcast by the satellite would require many people receiving, decoding, and comparing their results, mainly to identify any patterns in the satellite's behavior and the resulting demodulated data.

Derek and u/Xerbot are asking the SDR community to help collect more sample data, which might help in finding a way to decode some of the telemetry. If you have data to contribute, you can contact @ok9sgc on Twitter, and u/Xerbot on Reddit.

This reminds us of an old post from reader happysat where he demonstrated with an RTL-SDR that many "dead" satellites are actually still transmitting telemetry. Due to suspected chemical breakdown of the onboard batteries, the satellites tend to turn themselves on again when the solar panels receive sunlight.

Recently we came across the SATRAN project by Daniel Nikolajsen, which is an attempt to design, build and sell low cost kits of an automatic motorized satellite antenna rotator for less than US$200. A motorized satellite antenna rotator is useful for pointing high gain directional antennas such as a Yagi or satellite dish at low earth orbit satellites which can move across the sky quickly. This is also an idea used by the well known SATNOGS project which also provides a design for a 3D printed antenna rotator, and runs servers that archive received satellite data.

Compared to the SATNOGS design, the SATRAN design appears to be much simpler and easier to build. Although being a smaller unit it's only design to handle small compact antennas such as a 70cm Yagi. SATRAN is also controllable via a web interface and there is an Android App. The design is capable of rotating 360 degrees, and 110 degrees from zenith, which allows a user to cover the entire sky.

Daniel notes that SATRAN kits should be available for sale from Feburary/March 2021. He also notes that it is possible to 3D print most of the parts and to just purchase the electronics for a lower price.

More technical information about the project is available on it's Hackaday.io blog.

Back in November 2020 we posted about the release of a decoder for the FengYun line of geostationary weather satellites which provide full disk images of the Earth and are positioned to cover parts of Europe, Africa, the Middle East, Asia, Russia, and Australia. Back then only a few people had attempted decoding this, and it was believed that a 120cm satellite dish or larger would be required.

However, today on Reddit user u/Harrison_Clark55 has shown that it is possible to receive FengYun-2G with a typical 90-100cm WiFi grid dish. These WiFi grid dish's have proven to work well for other geostationary weather satellites such as GOES and GK-2A.

We do note that u/Harrison_Clark55's image appears to be missing a few lines of data, and they are based in Australia where the elevation of FY-2G could be quite high depending on what side of the continent they are on. So it's possible that receivers in lower elevations may still require a larger dish size to work.

There are already many image decoders for the NOAA APT weather satellites available, with the most common and feature rich program being the abandoned freeware "WXtoIMG".

However many people may not know how simple the APT digital signal processing code is. Over on his blog post Dmitrii Eliuseev explains how only 50 lines of Python code are required to decode an image from received APT audio. Dmitrii's post shows how a Hilbert transform is used on the APT audio which is essentially the entire decoding step. This is then followed by a for loop that calculates the pixel luminosity from the decoded data, and plots it onto an image file. 

Of course the image is only grayscale (or in Dmitrii's case he decided to use greenscale), but adding false color and various other image enhancements found in advanced software like WXtoIMG are just standard image processing techniques.

Dmitrii concludes with the following:

Interesting to mention, that there are not so many operational radio communication systems in the world, the signal of which can be decoded using 20 lines of code. The NOAA satellites are about 20 years old, and when they finally will retire, the new ones will most likely be digital and format will be much more complex (the new Russian Meteor-M2 satellite is already transmitting digital data at 137 MHz). So those who want to try something simple to decode can be advised to hurry up.

[Also mentioned on Hackaday]