uSDR is an embedded software-defined radio (SDR) board that is optimized for ease of use and collaboration. It incorporates WebUSB technology, which enables full functionality in the Chrome browser—under Linux, Windows, MacOS, and Android—without requiring specific drivers or software.

Software-Defined Radio Without All the Hassle

SDR is an emerging field that grows more accessible every day, but newcomers still face significant barriers to entry. uSDR lets you get started right away, without the need to install a new operating system, compile drivers, or troubleshoot version conflicts in software and vendor-support libraries. Just open a web browser and there’s everything you need! This is our vision, and it’s why we develop WSDR, the web-based SDR platform for researchers, developers, lab technicians, students, radio enthusiasts, and anyone else who’s curious about this powerful new technology.

We designed WSDR to be as flexible as possible so you can extend its functionality and bring more applications to life.

uSDR

We designed uSDR as a hardware showcase for the WSDR platform. (The u stands for µ, the Greek letter mu, and is pronounced "micro"). It’s a tiny board, in the M.2 2230 form factor, with A+E keys. This is a common format for Wi-Fi cards. All components are located on the top side, which simplifies thermal management. Built around the proven LMS6002 SDR chip from Lime Microsystems, uSDR provides the following features:

Features & Specifications

• M.2 2230 Key A+E interface
• Full-duplex TX & RX
• Frequency range: 300 - 3700 MHz (usable range typically starts from 230 MHz)
• RX/TX Bandwidth: 0.75 - 28 MHz plus bypass mode
• Clock stability: 0.5 PPM
• Sample rate up to 30.72 Msps (40+ Msps in bypass mode)
• High-Speed USB 2.0: 480 Mbps, streaming ~15 Msps half-duplex or ~5-6 Msps full-duplex
• Extended power supply range: 2.85 - 5.5 V
• Components on only one side of the PCB
• PCIe support in legacy mode
• MHF4 RF connectors

Host Interfaces

Even if your host doesn’t have an M.2 2230 A- or E- key interface, you can still use uSDR with the help of our adapters and our evaluation board. (If your favorite interface is missing from the list below, please let us know!)

¹ The standard specifies optional USB 2.0 lines for M keys but we have yet to find them routed in a host
² Off-the-shelf, USB Type-A-to-Mini-PCIe & Mini-PCIe-to-M.2-2230-A/E adapters

Interfacing through USB 2.0 doesn’t mean that your SDR has to be in close proximity to your host. Just pick up a USB 2.0 extender, position the uSDR up to 60 m away from the host, and connect the two using twisted pair or coaxial cable.

uSDR Components

It took us three hardware revisions to get the board right. The main challenge was to ensure proper signal integrity and to fit all of the components on just one side of the board.

uSDR includes the following components:

• RFIC: LMS6002D
• FPGA: XC7A35T
• Crystal oscillator: ASTX-13-C-26.000MHZ-I05
• Clock buffer: PL133-27
• Clock generator: SI5332A
• USB 2.0 PHY: USB3333
• RF Baluns: B0322J5050AHF + 3600BL14M050
• RF connectors: MHF4
• RF switches: BGS12P2L6

As some of our subscribers have noted, the initial revision included an additional upconverter mixer and RF connector to cover LF frequencies. Its performance fell below expectations, however, so we removed it. We’ve also exposed JTAG and 12 GPIO pins using some extra M.2 A+E key reserved pins. Finally, we exposed the external reference clock and routed the LNA3 input of the LMS6002D to M.2 pads. With one GPIO as 1PSS, it’s possible to synchronize multiple boards for a multi-channel array.

uSDR Block Diagram

uSDR Pinout Diagram

Comparisons

¹BTS, eNB or gNB via srsRAN, OsmoBTS, etc.

uSDR Accessories

We’ve also designed various adapters and expansion boards for uSDR.

M.2 B+M Key to M.2 E Key Adapter

It’s hard to find this particular adapter, so we made our own. It’s 22-mm wide and has 80/60/42 screw position to support the M.2 2280, 2260, and 2242 form factors. It contains no active components, so you can just trim off whatever portion of the adapter you don’t need.

Mini PCIe to M.2 E Key Adapter

There are plenty of Mini PCIe adapters out there, but we made this with a few extra features, including:

• The ability to route two PCIe lanes instead of just one
• Six GPIOs exposed to an FPC cable, along with 1.8 V
• A connector for an external reference clock
• Mounting holes for a heatsink

USB Adapter

We designed our USB adapter so that it’s capable of supporting USB 3.0, should we manage to implement that before entering production (or perhaps for a future revision of uSDR). with an RX-TX optional loopback path for advanced calibration, and many other features, including:

• Six GPIOs exposed to an FPC cable, along with 1.8 V
• TX harmonic-reduction filter for 2.3 - 3.7 GHz
• RX LPF at 3.5 GHz
• A connector for an external reference clock
• Exposed JTAG pads for a JTAG-HS2 adapter
• Mounting holes for a heatsink or enclosure

Development Board

This board was designed for developers and advanced users. It has USB Type-C connectors and can be plugged into a computer with a PCIe x4 slot. It provides the following features:

• A very simple radio fronted that allows you to prototype using the 2.4-GHz ISM band
• Duplexers for common cellular bands
• Increased TX power
• Increased RX sensitivity
• Extended automatic gain control (AGC)
• More precise clock synchronization thanks to a GNSS module.
• Mounting holes for a heatsink or enclosure

Development Board Technical Specifications

• GPSDO: GNSS module + 12-bit DAC for VCTCXO
• GPIO: 12 GPIOs in six banks with different voltage levels (1.8 - 5 V)
• PSRAM: 64-Mbit PSRAM
• USB Type-C: 5 V, 3 A (USB 3.0 lines routed, currently without gateware support)
• RF filters:
  • 3.0 - 3.8 GHz
  • 2.1 - 3.0 GHz (ISM, Wi-Fi, Bluetooth, Zigbee )
  • 0 - 2.1 GHz
  • 0 - 1.2 GHz
• TX filters:
  • 0 - 3.8 GHz
  • 0 - 2.1 GHz
  • 0 - 1.2 GHz
• LNA/PGA: MiniCircuits PGA-103+

Development Board Frontend Block Diagram

The WSDR Architecture

Modern browsers support WebUSB technology, which allows direct communication between your browser and a USB device. Data processing is done locally.

The web is no longer slow! The JavaScript execution unit in modern browsers is powerful enough to run Linux. Even better, you don’t have to limit yourself to JavaScript. With WebAssembly and the Emscripten project, you can write code in C, C++, Rust, Go, or C#, which makes it easier to port existing applications to the web. And WebAssembly supports the SIMD Extensions, so you won’t even have to sacrifice DSP performance. And the list goes on. WebGPU technology allows your browser to leverage the power of your GPU, for example, and progressive web apps (PWAs) allow your browser-based software to function without an Internet connection.

WSDR is an extensible framework upon which you can run applications. We think of it in terms of three layers:

1. Low level - Libraries for basic DSP functions, data manipulation, and hardware abstraction
2. The platform level - APIs for various services like configuration, data sharing, data storage, offloading intensive processing tasks, etc.
3. The application level - Where you define your data pipeline, data visualizations, and visual control blocks.

We will talk more during the campaign about how you can extend this platform to suit your own applications.

WSDR applications can receive data directly from uSDR hardware or from a remote source. Remote streams currently work over WebSockets, and we’re planning to accommodate WebTransport in the future (the primary advantage of WebTransport being support for UDP communication).

Applications Like Spectrum & Signal Analyzers, FM Demodulators, Visualization Tools, and More!

We have developed several ready-to-use applications, and we’d love to hear your feedback about what features and applications are most important to you. So far, we have implemented the following applications:

• A spectrum monitor
• A signal analyzer
• A PMR receiver
• An IQ playback application
• An IQ recorder
• An IQ signal generator

Signal Analyzer

Signal Analyzer is a tool for understanding wireless signals. It has various data visualizers to help you identify interesting signals. It also has a number of built-in demodulator and data-packet interpreters. It can demodulate FM, PSK, MSK, and FSK—among other examples—to produce a bitstream. Then the bitstream can be packetized using nRF, LE, Bluetooth, and other packet parsers.

You can receive IQ data from a uSDR or from a remote stream, then you can record it or analyze it. The parsed data can be downloaded in hex or binary.

Spectrogram & Monitor

Spectrogram and Monitor are spectrum-monitoring apps. They allow you to configure FFT size, FFT window function, accumulation, and other uSDR parameters. FFT is currently done in the browser, but we’re working on getting it into the FPGA to maximize bandwidth.

Simplifying Collaboration

Do you want to give others access to your radio-spectrum data? uSDR makes it as easy as sharing a link. Anyone with the link can access, record, or analyze the spectrum, but they will not be able to modify parameters such as bandwidth, sample rate, and gain settings.

It’s also possible to share the device, allowing the person with the link to have exclusive access and the ability to change any parameter they like.

Managing a large number of recordings can be challenging, especially when you need to download them from the cloud to make use of them. To help with this, WSDR has native support for working with cloud storage services. We have implemented a simple file-storage backend and would appreciate hearing your preferences regarding data storage providers that you would like us to add.

Work Locally With WSDR & GNU Radio or Remotely through Node.js

We made special gr-wsdr blocks, so you can stream data to and from the WSDR platform. This connection works over WebSockets, and if you run GNURadio locally, your data will processed locally. Accessing uSDR and SDR DSP libraries is also possible through Node.js. And WebUSB works seamlessly in Node.js, which gives you the flexibility to deploy your application wherever you like.

A Cellular Network in Your Browser? Not a Problem!

Spectrograms, analyzers, and modulators do not fully showcase the capabilities of WSDR. To demonstrate its true potential, we have also developed a sophisticated web-based application: a 2G cellular network based on the Osmocom stack. (We opted for 2G because it allows you to connect to your network without a special SIM card.) Our biggest challenge was achieving predictable jitter for radio-frame processing, but we worked it out and managed to stand up a network that can last for days without issues.

There are still geographic regions that lack mobile coverage. And there are circumstances—even in advanced economies—where existing coverage lets us down. Making it easier to deploy a network is one way to bring us closer to the goal of providing coverage for everyone, all of the time. You can even run a network from the browser on your phone! Why not have one in your pocket, just in case?

Working Toward a Trusted Wireless Communication Network

Many large wireless-communication vendors rely on closed ICs, binary firmware blobs, pre-compiled software, or all three – to the point where it is nearly impossible to verify that everything works as advertised. Over the past decade, it has become increasingly important that we start building trusted communication platforms. The key to establishing trust lies in transparency: in having access to all parts of the system. Different groups have begun confronting different aspects of that challenge, focusing their efforts on everything from CPUs to PCBs.

Remember Openmoko? Had a look Precursor or MNT Reform and Pocket Reform? There are many such projects, and the best of them are making solid progress. But they lack access to trusted wireless solutions. Wi-Fi cards, GSM modems, and nRF chips still rely on binary blobs to operate. Initiatives like Osmocom, srsRAN, and openwifi are working on it. And so are we. We’ve noticed a distinct lack of small communication modules—devices comparable to Wi-Fi cards—that can be used by trusted hardware to create or communicate with trusted networks. We intend for uSDR to help fill that void.

And just having open-source FPGA code isn’t enough, as not all FPGAs can be programmed using an open-source toolchain. For example, the open-source toolchain for the 7-Series is currently missing some features, which is why we’re working with Symbiotic EDA to improve it. uSDR will have fully open-source support for USB mode by the time it ships.

Unfortunately, we can’t say the same for PCIe. Our PCIe firmware will be closed source to begin with, as will other features for which there is currently no open-source solution. We will be expanding our open-source coverage as openXC7 evolves. In addition, while projects like Osmocom and srsRAN won’t be a problem, software-defined Wi-Fi projects like openwifi and bladeRF-wiphy will require a dedicated porting effort. We’d love to take this on, but we can’t commit to it until we see how the campaign goes. Stay tuned!

Bring New Life to Old Hardware

To get started with uSDR, all you need is a browser and a USB port. Got an old laptop sitting around? Maybe one that doesn’t even have a hard drive in it? That’ll work. Just boot it from a USB stick, install Chrome, and connect to the local WSDR platform. All your apps and settings will be stored in the cloud.

Or you can use an Android smartphone or tablet, as long as it supports the USB OTG specification, which is relatively common. For older devices, you will probably need an OTG Micro-B to USB Type-A cable, preferably with a dedicated power port so you can keep your device charged at the same time. You can also find USB Type-C to USB Type-A adapters, with dedicated power, though they might not support "fast charging."

Or Just Use It Like a Traditional SDR…

You can operate uSDR the same way you would any other SDR board, thanks to a native C library and SoapySDR support. That means all of your favorite applications will work seamlessly, including GNU Radio, srsRAN, OsmoBTS, and GQRX, to name just a few examples.

You can also connect to uSDR natively, from a Linux 5.4+ host, through an PCIe interface. To do so, you will need to compile and load our kernel driver, and the USB interface will become inaccessible. (If you connect through USB, you can operate uSDR without additional drivers.)

Interested in traditional applications for uSDR? Let us know!

Help Us Build A Community Around uSDR

We want to make uSDR more affordable but we also want to provide all of these exciting features. (And more!) Reducing the price would require a large manufacturing run, which would translate to a very high funding goal, which would increasing the likelihood that we fall short. Instead, we decided to set a minimal campaign goal, hold ourselves back from promising certain features, and introduce a number of stretch goals. If we hit certain funding targets, we will begin adding features. Subscribe to the project, follow our campaign updates, and learn more about these stretch goals as we announce them!

Support & Documentation

Please visit our GitHub for host library installation and other uSDR tools.

Information about adapter features and installation can be found at docs.wsdr.io.

If you have questions or suggestions, you can reach us using the Ask a Technical Question link toward the bottom of our campaign page.

uSDR is an open source project with many different elements. Below is a table of the corresponding licenses:

¹ Altium project files, Gerbers, BoM, etc.