OTA: LimeSDR GPIO, Mini Give-away, SpaceX Sats and More

The LimeSDR General-Purpose Input/Output (GPIO) Board, designed to make it easier to interface the LimeSDR with external hardware, is beginning its journeys to backers following a minor delay in the assembly process.

Designed to expand the LimeSDR’s capabilities, the GPIO Board provides individually-configurable bi-directional level-shifted input/output pins for the GPIO pins 0 through 7 inclusive of the LimeSDR’s field programmable gate array (FPGA). Each pin of the GPIO Board includes high-voltage and power Darlington drive stage suitable for inductive loads including coaxial relays, reducing the complexity of working with the FPGA’s GPIO pins to drive external hardware.

Following completion of assembly and testing, the boards have now begun shipping to crowdfunding site Crowd Supply from where they will begin to reach backers – and hopefully a few of those backers will be sharing their creations over in the forum!

For those interested in the LimeSDR Mini-powered Internet of Things (IoT) development kit, created in partnership with Seeed Studio, EE News Europe is offering a chance at walking away with one of five full packs in a competition running through to the end of the month.

Designed primarily with education and research in mind, each kit includes a LimeSDR Mini with antennas optimised for use in the industrial, medical, and scientific (ISM) unlicensed bands, a Grove Pi+ add-on board for the Raspberry Pi family of microcomputers, and a range of input and output boards compatible with the Grove connectivity standard.

Full details on entering the give-away are available on the EE News Europe website.

Simon Brown’s SDR Console software is now available in a V3 Beta build, marking its departure from Preview status and feature completion ahead of a full release scheduled for early April.

Designed to replace SDR Console V2, the improvements over its predecessor are many: the software’s graphical interface is now hardware accelerated via the DirectX API suite to improve responsiveness and lower the load on the system CPU, a switch to WASAPI audio has reduced latency, the software now supports up to 24 simultaneous receivers, and has better support for remote servers. Internally, the software has been restructured to make it easier to maintain – as Simon has it, a “future-proof design.”

SDR Console V3 Beta 1 is available for free download now from the official website, while a second beta build is scheduled for release in early March and the formal launch in early April 2018.

Anyone looking for a beginner-friendly introduction to SDR technologies should have a look at P. Lutus’ introductory article, brought to our attention by RTL-SDR.

“It’s not even a slight exaggeration to say we’re witnessing a silent but widespread revolution that joins mathematics, electronics and everyday reality,” the article begins. “This revolution shows the degree to which physical reality is innately mathematical. This article covers available SDR hardware, software and configurations, but it also teaches a little radio theory and mathematics, the kind of mathematics we all need to understand to avoid being pushed aside in a more mathematically adept future society.”

Topics covered in the article include a look at some common SDR devices, popular software, and concepts including the frequency domain, vectors and vector conversion, and IQ data.

Hackaday, meanwhile, has highlighted a video from Grant Sanderson explaining the concept behind the Fourier transform, the splitting of a waveform into its frequency components and vice-versa.

“While most of us will know what a Fourier transform is, fewer of us will know anything of how one works. They are a function called from a library rather than performed in themselves,” explains Hackaday’s Jenny List by way of introduction. “Even when they are taught in schools or university courses they remain something that not all students ‘get,’ and woe betide you if (as your scribe did) you have a sub-par maths lecturer.

“You may still only use Fourier transforms through a library, but after watching this video perhaps some of their mysteries will be revealed.”

The GNU Radio project has announced GREP, the GNU Radio Enhancement Proposal process, through which it hopes to better plan new features to be added to the popular package.

“For big feature development, we need a way to plan development and coordinate it between contributors, maintainers, and lead developers,” explains GNU Radio’s Martin Braun of the reason behind the new approach to development. “This is the first big reason to introduce GREPs: They are a platform for discussing feature development, publicly, ahead of time.

“GREPs are so much more, though. They give us a tool to codify things such as coding guidelines, but with a clear way of putting them up for discussion. And they don’t have to be technical; enhancement proposals to the GNU Radio organisation itself can also become GREPs. We distinguish between GREPs that are technical enhancements, organisational changes, and informational documents.”

It is hoped that the GREP process will make the development of GNU Radio both smoother and more transparent while also assisting those looking to contribute.

At the same time, GNU Radio has announced its acceptance into the Google Summer of Code 2018 and is actively seeking students eager to participate in the programme.

“GSoC is a great opportunity for students, but equally important for GNU Radio as it helps us to find new and valuable contributors with fresh ideas that help us to further the project’s development,” explains GNU Radio’s Felix Wunsch. “If you’re a student and interested in participating in GSoC, head over to our ideas list and see if there’s a project that you’re interested in – there’s a lot of great project ideas! You’re into Python? Improve our gr_modtool, our out-of-tree creation tool that is used by so many developers! You prefer some number-crunching DSP? Why don’t you have a look at gr-radar or gr-inspector, a module for blind signal classification? You like making shiny GUIs with Qt? Create a nice app for viewing DTV and show the world what GNU Radio can do!”

The full ideas list can be found on the GNU Radio wiki, along with details on applying to the programme.

Ofcom, the UK’s communications regulator, has announced that the auctioning off of radio-frequency spectrum for use with 5G services will take place this April, despite objections from UK mobile network Three.

The UK’s 5G auction will see networks bidding for a share of the underlying radio-frequency spectrum, but with a restriction that sees no single network being able to acquire more than 37 percent of the available spectrum. Smaller mobile network Three had previously petitioned to have this limit reduced further to 30 percent, out of concerns that its larger rivals could effectively block it from competing on a level playing field.

In an update on the process (PDF warning), regulator Ofcom confirmed that the auction will proceed with the original 37 percent limitation in place following the rejection of Three’s petition by the Court of Appeal.

In other 5G news, the EDN Network has published a look at how hybrid beamforming will assist with the roll-out of 5G multiple-input multiple-output (MIMO) arrays ahead of the standard’s commercial availability.

“Designers have two options for beamforming, one more practical than the other. If cost and power were not constrained in 5G systems, dedicated receive and transmit paths could be added for each MIMO array element,” explains Rick Gentile in the article. “This type of ‘all digital’ beamforming architecture would provide the most flexibility from a system-level standpoint to form beams in large multiuser scenarios.

“Cost and power are constrained, however, and that leaves hybrid beamforming – ‘hybrid’ in that analogue phase shifters are integrated with the digital circuitry – and whenever digital and analog are integrated, that’s another place where a system-level approach to design is recommended.”

Private spaceflight company SpaceX is reportedly due to launch the first in a planned constellation of microsatellites designed to provide global broadband internet connectivity this weekend under a programme dubbed Starlink.

According to US Federal Communications Commission documentation first spotted by CNET, the first of SpaceX’s Starlink satellites will be included on board a Falcon 9 rocket which is scheduled to launch this weekend alongside its primary payload of the Paz imagery satellite.

The two satellites, dubbed Microsat-2a and Microsat-2b and acting as revisions of the originally-developed but never-launched Microsat-1a and 1b designs, will be used as a testbed platform for the Starlink service’s public début planned for the middle of 2020.

Lockheed Martin has announced it is opening up specifications for its own satellite platforms as a means of encouraging innovation in the space industry.

“Our goal with Lockheed Martin Open Space is twofold: first, to help more companies and innovators do amazing things in space, and second, to create new avenues for collaboration so we can move faster to tackle our customers’ most pressing challenges,” explains Rick Ambrose, executive vice president of Lockheed Martin Space, of the programme. “We’re not just offering launch slots, we’re ready to help new companies integrate their groundbreaking technologies with powerful satellite platforms. We believe there’s significant untapped potential out there waiting to be unleashed.”

The programme is open for anyone developing non-proprietary technologies to “help protect, connect, and inspire the world,” Lockheed Martin has claimed, with suggested projects including ” helping first responders address crises faster, studying the environment, creating ultra-high-capacity communications links and adapting low-cost commercial technology to the punishing environments of space.”

More details are available from the official project page, where interested parties can submit concepts between now and the 11th of May 2018.

Finally, Internet of Things (IoT) specialist Particle has announced the impending launch of a trio of development boards featuring mesh networking: the Xenon, Argon, and Boron.

Building on the company’s existing development board designs and the popular Adafruit Feather board layout, the base Xenon includes Bluetooth Low Energy and mesh networking capabilities; the Argon includes added Wi-Fi connectivity for use as a gateway within the mesh; and the Boron adds a choice of 4G Long Term Evolution (LTE) or 2G/3G cellular connectivity.

“Many IoT products today have the processing power of a smartphone but lack access to the environmental data and context they need to make the best decisions,” Particle explains. “Particle Mesh hardware is inexpensive, battery-friendly, and resistant to failure, which makes it easy to add wireless sensors to your IoT product and ensure it has the information it needs to make intelligent choices.”

The company has launched pre-orders for the boards at reduced pricing of $9 for the Xenon, $15 for the Argon, and $29 for the LTE version of the Boron.

Focus On: Evariste Courjaud

Evariste Coujard

OTA’s Focus On is a series of interviews with notable members of the Myriad-RF and wider software defined radio community. If you’d like to nominate someone to be interviewed, or would like to be interviewed yourself in a future OTA, send your proposal to mailto:ota@myriadrf.org.

Evariste ‘F5OEO’ Courjaud’s introduction to the skills and concepts that would, eventually, bring him to the world of software defined radio was, initially, of little personal interest. “I graduated from an electronics and computer engineering school. That was not a pleasant time: maths and electronic fundamentals were not very sexy at the time,” he explains. “It should have been a period of heavy, deep learning, but I didn’t see the sparkle I would need until years after!

“Out of school, I set up a small company – no, at that time we didn’t call them start-ups. Working first on drivers for our custom PC ISA which timestamped video tape and controlled a VCR via an infra-red controller, I moved to a study of digital set top box interactive applications – something like the Red Button services in UK. I wrote my first MPEG-2 dedicated encoder, optimising it for still pictures – what a weird thing for a movie standard! The DVB [Digital Video Broadcasting] standard became my main book, even focusing to the transport stream layer – though I stopped before getting into channel encoding and RF modulation. Then it was into broadcast products: video mosaic, data streamer, multiplexing, video encoding and interfacing to professional TV modulator products.”

Evariste’s introduction to radio itself, by contrast, was rather more electrifying – literally. “I was shocked at the age of seven with a high voltage from an RF power amplifier not well protected thanks to my kindly father, call-sign F6DZP. At this time, fields like those of the TRS-80 computer or HF SSB radio were very similar, and I grew up with that,” Evariste recalls. “I was more playing with electronic kits to build multi-vibrators plugged to my MSX computer which emulate a joystick for winning my video games – Olympic Games – than trying to use radio for communications. Slow Scan Television (SSTV) was the exception, especially when I received pictures from Australia. I passed my ham radio licence during high school, having at the same time fun building a radio kit – HW101 – which has never been finished!”

From amateur radio, it’s a short jump to software-defined radio for one very obvious reason. “SDR is a fantastic opportunity for amateur radio, mainly because it simplifies experimentation,” Evariste explains. “Building a transceiver with blocks on GNU Radio instead of soldering hardware could attract some ‘handshake’ people like me. But ‘SDR inside’ is not a proof of quality if we don’t have access to the firmware, as we had access to schematics in the early ham days. Amateur radio is a community which try to share its knowledge: SDR allows this knowledge to be spread very easily over the internet – and, hopefully, one day over Hamnet, an independent network).

“SDR is a challenge for the actual amateur radio community,” Evariste admits. “These are highly skilled electronics and radio people, but usually without a software background. SDR has brought us to a transitional age where we can still learn from each generation. We still need to know how to build analogue filters, front-ends, and LNAs before going to our DSP through an analogue to digital converter. Without this collaboration in mind, the future is going to be very uncertain.”

Amateur radio itself, Evariste explains, is an important effort in the days of SDR. “Radio-frequency (RF) spectrum is very valuable,” he says. “Thus, access to RF is very constrained. Even using ‘free frequencies’ – ISM – is not free for playing, as you need to have hardware compliant with the standard to use it. The only way to legally play with RF and experiment with custom hardware/software is to get an amateur radio licence – though, of course, there are lot of other reasons to get involved with ham radio.”

Asked to name his proudest SDR-related achievement, there’s little surprise to find Evariste’s projects relating to his professional development history – from which, he jokes, he is retired for “experimental reasons.” “My first DVB transmitter using the Raspberry Pi’s general-purpose input-output (GPIO) header, received by a commercial set-top box. At the time I was really new to SDR. Using harmonics from a square wave signal to be received on L-band was a ‘lucky’ chance, as the QPSK modulation spectrum doesn’t spread over harmonics. This makes me confident with SDR techniques and I begin to meet people that explain in detail what I experienced experimentally.”

Evariste’s experimentation platform has changed with time. “For several years I developed on Visual C++ running on a Windows PC. Being too lazy to learn a new platform, I missed the Linux wave until I began to play with the Raspberry Pi,” he explains. “Using it as a normal computer was not my target, as it gives us access to the world of external hardware through its GPIO port. When I heard about PiFM, which could transmit HF, I was very proud to learn how it works. After hours of storming I wrote rpidatv, an ugly DVB modulator using GPIO – Nyquist is my friend – and few months after wrote a minimal IQ SDR transmitter called rpitx. Trying to use hidden or alternate functions from a device like the Raspberry Pi is a very fun challenge. As I prefer ‘proof of concept,’ I usually write some very bad code – pull request are always welcomed! I mainly develop in the old-school C language – Python is too cool, so I don’t use it. The hardware salad is made of Raspberry Pis and SDR units from several manufacturers – and the LimeSDR Mini has proven a very tasty fruit to add to the mix!

“I closely follow projects in which the SDR is aided by a system’s graphics processor,” Evariste explains of the progress he’s eager to see in the SDR world, “like the DVBS2-X receiver from Charles Brain G4GUO and cloud-sdr from Sylvain Azarian F4GKR. FPGA-specialised functions should also offload from the CPU, but are not so easy to set up. Deep learning on signals is also of huge interest. Edouard F4EXB is a must-follow person, too, thanks to his SDR Angel software and Pascal F4DAV for his lean approach for DVB receiving on embedded platforms, leandvb.

For those eager to dip their toes into the world of amateur radio, whether using traditional transceivers or their software-defined equivalents, Evariste has some advice. “Think about learning and experimenting before targeting active communication. Buying a ‘commercial all-mode transceiver’ should not the ultimate goal, even though communicating with others may be a fun way to operate at early stage. The spirit of the radio amateur is learning, even at the most basic levels depending on your skill. Communicating without that in mind could result in the very ’empty’ communication we often hear on ham radio bands. There are some very little funny kits to experiment with: Bitx or, for analogue, Pixie. Choosing to start with starting with SDR or analogue radio is not important: be aware of both to feel the global RF concept.”

Evariste himself, meanwhile, is working to get as close to the underlying hardware as possible. “SDR in amateur radio usually means GNU Radio,” he explains. “Contributing to GNU Radio is a challenge I am too lazy to accomplish. I prefer KISS [Keep It Simple, Stupid] projects to begin with: that’s why I directly use the LimeSDR API instead of using multiple layers software like SoapySDR. Right now I’m even thinking of bypassing the API to be as close as possible to the RF hardware. FPGA customisation and microcontroller use will surely be the ultimate goal – in my next life!”

For Evariste, there’s only one real area of concern. “I am very scared about high RF power, as I can already make some big mistakes with low currents! I ask the community to help me when I am not very confident on a particular area,” he admits. “For now, my antennas are on the ground after a heavy tempest. Still too lazy – again – to mount them up, I am designing a remote SDR site which is already at 50 meters high. All ideas are welcomed!”

Evariste’s code can be found on his GitHub repository.

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