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Open source SDR board teams up with Snappy Ubuntu

May 2, 2016 — by Eric Brown — 2,646 views
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[Updated: May 3] — The open source LimeSDR board supports user-defined radios ranging from ZigBee to LTE, under control of a USB-interfaced system running Snappy Ubuntu Core.

UK-based Lime Microsystems, which develops field programmable RF (FPRF) transceivers for wireless broadband systems, has launched an open source software defined radio (SDR) board on CrowdSupply. Like other Linux-based SDR systems we’ve seen, the LimeSDR uses an FPGA to help orchestrate wireless communications that can be tuned, manipulated, and reconfigured to different wireless standards via software. The LimeSDR’s FPGA manages DSP and interfacing tasks, while a USB 3.0-connected host SBC or other system running Snappy Ubuntu Core provides user interface and various high-level supervisory functions.

LimeSDR with four antennas
(click image to enlarge)

The device can be used as a low-cost multi-lingual cellular base station or as the guts of an IoT wireless gateway that can handle any wireless standard you can throw at it. Other applications include academic, industrial, hobbyist, and scientific, such as radio astronomy.

The LimeSDR can send and receive using UMTS, LTE, GSM, WiFi, LoRa, Bluetooth, Zigbee, RFID, Digital Broadcasting, and many other standards, says the company’s community project. is part of Lime Micro’s Myriad-RF project for open source wireless communications.

The CrowdSupply campaign ends June 21, with the $299 board shipping Nov. 30. Models with cases, cables, and antennas ship Oct. 31 for $499 (acrylic) or $599 (aluminum). A $799 version of the board with a PCIe interface ships Nov. 30.

LimeSDR front (upper) and back (lower) views
(click images to enlarge)

The LimeSDR operates in conjunction with a USB-connected SBC or other system running Canonical’s lightweight, transaction-capable Snappy Ubuntu Core Linux distribution, which manages the board’s Altera Cyclone IV FPGA. The Cyclone IV features up to 115K vertically arranged logic elements, 4Mbits of embedded memory arranged as 9-Kbit (M9K) blocks, and 266 18 x 18 embedded multipliers.

Some other recent SDR devices include the ValentFX KiwiSDR BeagleBone Cape, Avnet’s PicoZed SDR COM, and the new Epiq Solutions Matchstiq S10.

Block diagrams: LimeSDR (left) and Cyclone IV FPGA
(click image to enlarge)

The open source LimeSDR is about a quarter of the way to its half-million dollar goal, but the project has already signed up one early customer with EE, the UK’s largest mobile operator. In a trial project, EE plans to deploy the device in remote areas as micro 4G basestations mounted on existing infrastructure like lighthouses, high-buildings, and mountains, or even balloons and drones.

Canonical is participating in both the LimeSDR and EE projects. Canonical’s head of IoT, Maarten Ectors recently showed off an interesting SDR-enabled projector system built around the board.

With Snappy’s built-in support for an app marketplace, LimeSDR apps can be easily shared and sold, says the LimeSDR project. The board’s host driver architecture, meanwhile, supports both the SoapySDR and UHD APIs. The firmware supports advanced features liked timed TX bursts and RX sample timestamps, “as required for use with GSM and other time-sensitive protocols,” says the project. The LimeSDR’s host driver is built on a “Lime Suite” low level library that handles programming and calibration of the LMS7002M FPRF transceiver, among other gnarly internal communications.

LimeSDR in its optional acrylic (left) and aluminum cases
(click images to enlarge)

Other open source components include the Pothos dataflow programming software suite and GNU Radio. An open source Altium design database for LimeSDR is available, along with the USB controller firmware, and FPGA RTL. The project also plans to release a KiCAD recapture and layout document of the device.

LimeSDR Specs

The 100 x 60mm LimeSDR supplements its Cyclone IV FPGA with 256MB of DDR2 RAM. There’s also a USB 3.0 port — or optional PCIe — for connection to an external SBC or other system. The board’s Lime Microsystems LMS7002M 2×2 MIMO transceiver has a continuous frequency range of 100kHz to 3.8GHz, as well as 61.44MHz bandwidth, and up to 10 dBm output.

Specifications listed for the LimeSDR board include:

  • FPGA — Altera Cyclone IV EP4CE40F23, which features:
    • 39,600 LEs
    • 126 M9K memory blocks
    • 1,134 Kbits embedded memory
    • 116 18-bit x 18-bit multipliers
    • 4x PLLs
    • Up to 532 user I/Os
    • Up to 224 differential channels
  • Memory — 256MB DDR2 SDRAM
  • Wireless:
    • RF Transceiver — Lime Microsystems LMS7002M MIMO FPRF
    • Oscillator — Rakon RPT7050A @30.72MHz
    • Continuous frequency range — 100kHz to 3.8GHz
    • Bandwidth — 61.44MHz
    • RF connection — 10x U.FL connectors (6 RX, 4 TX)
    • Power output (CW) — up to 10 dBm
    • Multiplexing — 2×2 MIMO
    • Antennas — Optional 4x omnidirectional, bendable, with SMA, plus U.FL to SMA cables; pre-tuned to 800-960MHz, 1710-2170MHz, and 2400-2700MHz
  • Other I/O — USB 3.0 port (or optional PCIe bus)
  • Other features — Programmable LEDs; optional acrylic or aluminum cases
  • Power — via USB port (or optional PCIe bus)
  • Dimensions — 100 x 60mm (USB version)
  • Operating system support — Snappy Ubuntu Core (Linux), running on USB-connected host system

Further information

The LimeSDR board is available on CrowdSupply through June 21, starting at $299, with most shipments due Nov. 30 (see farther above for details). Shipping is free to the U.S., or $15 elsewhere. More information may be found in the LimeSDR CrowdSupply page and the site.

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