Benefits of using 4Links SpaceWire Test Equipment / EGSE

Here are some of the unique benefits of 4Links SpaceWire Test Equipment, for users and projects:

Bug Detection and Resolution

  • 4Links test equipment has detected bugs, in many SpaceWire designs, that have remained undetected in months of simulation and test.
  • 4Links equipment has often quickly enabled users to solve long-standing problems that other test and/or simulation techniques have failed to solve.

Design and Build Quality

  • 4Links' SpaceWire implementation has been stable since 2003. No other SpaceWire implementation has comparable maturity.
  • 4Links equipment works out of the box. Customers do not have to debug it.
  • Internal voltages and temperatures are monitored continuously to detect drift and hence to suggest preventative maintenance ahead of failure.
  • 4Links ensures that its test equipment cannot damage flight equipment, e.g. with separate LVDS buffers for each port, and current and voltage limits for each buffer.
  • Using 4Links test equipment, interfaced to host computers using Ethernet, it is possible to build an EGSE system with a single ground point and no earth loops. This is much more difficult to achieve when the SpaceWire interfaces are connected to the host computers using the USB or PCI busses.

Cost effectiveness

  • The same hardware can be customized, via a memory card plugged in to the front panel, to perform a wide variety of functions that are useful at different stages of a project. There is often no need to buy new hardware, resulting in major cost savings over the life-span of a project.
  • Interfacing to Ethernet and IP, 4Links equipment can be used with your choice of computer and operating system. It has been used successfully with different versions of Windows, different builds of Linux including real-time, and Solaris. Untried operating systems have been up and running within hours of the equipment arriving.
  • Your choice of computer and operating system may change during the life of the project. The Ethernet and TCP/IP interfaces allow you to change, without the costs of having to maintain obsolete computers.
  • Because 4Links test equipment interfaces via the Internet, users can be physically remote from the equipment under test (EUT). Testing can be from an office in the same building, from another building, another company, or another country or continent, saving travel and making it possible to find and fix problems sooner, saving bugs, time and money.

Usability

  • 4Links equipment has a clear and bright front-panel display that gives information about the state of the equipment, the interface to Ethernet and of each port, including speed and traffic in each direction. Many users have commented how comprehensive and useful this information can be.
  • 4Links provides software that can easily be parameterized to perform different tests. These are provided as Java files which will run on almost any computer, or as executables and C source. An API is also provided in C source for users to write their own test programs, often based on the example test program that is supplied.

Performance

  • The SpaceWire transmit speed can be set in small increments up to 498Mbits/s (for -RG4xx products), and the receive speed is good on most of our products to well above 450Mbits/s.
  • 4Links -RG4xx Ethernet-to-SpaceWire products can saturate a bidirectional 200Mbits/s SpaceWire link, even when transmitting and receiving packets as small as 10 bytes. At these speeds, the limitation is the CPU processing load on the host computer, which peaks at around 4.5Mpkts/s, not the EtherSpaceLink unit itself.

Functionality

  • A simple bridge (ESL-RG201) is available from the computer/Ethernet to a single port, to up to eight SpaceWire ports on a single box up to any number of SpaceWire ports on multiple boxes.
  • All the bridges are able to relay SpaceWire traffic to a host computer, where they can be recorded and replayed.
  • The Multi-Link SpaceWire Recorder (MSR) provides even more convenient recording of multiple SpaceWire links, together with time-tags, as a complete record of a network's traffic.
  • The simple bridges can be augmented by optional SpaceWire functionality such as Time Codes, and/or by a wide range of instrumentation and diagnostics.
  • The clocks on multiple 4Links EtherSpaceLink units can be synchronised to an accuracy of typically 3ns, allowing time-tags to be consistent across a large test system to a resolution of one bit period or better.
  • A highly flexible SpaceWire routing switch can emulate multiple switches with one unit or a single switch with more than eight ports, and can gather traffic statistics for each port.

Diagnostics

  • Waveforms can be captured of the wire signals on the occurrence of a wide variety of events, particularly violations of the SpaceWire standard. These are displayed as waveforms with full decode of bits, SpaceWire tokens, and characters, for a period before and after the event. A time-tag reports the time at which the event occurred. Waveform files can be saved for subsequent, off-line, analysis.
  • Error Injection makes it possible to test for the correct response to error conditions. 4Links error injection is precise.
  • 4Links equipment in its normal running creates conditions which are fully permitted in the SpaceWire standard and that will inevitably occur at some point in a space mission, even if they occur rarely. Other designers may not realize that these conditions can occur or may treat them as corner cases that will be sufficiently rare that they can be ignored. 4Links maintain interoperability with such designs, but can zero in on such corner cases remarkably quickly.
  • SpaceWire routing switches include arbiters between their asynchronous input ports. Functional testing of such arbiters requires packets to arrive at multiple ports at the same time. That is only possible with Output Synchronization from the 4Links Diagnostic SpaceWire Interface or SpaceWire Packet Generator.
  • A simple diagnostic aid is to record traffic to and from one or more ports. 4Links provides selective replay of such records, for reproducing error conditions, for regression testing, or for later analysis when a problem comes to light that may have been missed earlier, but for which the records make information available.
  • Pre-tested subsystems sometimes do not work together, and the problem may not be found until late in integration. The Multi-link SpaceWire Analyzer monitors traffic over four links at exceptionally low cost per link. The traffic statistics and time-tagged error waveforms have proved to be excellent at resolving the demarcation issues when two or more such devices are brought together.

Instrumentation of Time

  • Time-tags are important to the space industry. 4Links has long offered time-tagging in our test equipment and has progressively improved the resolution from 100ns down to 1.4ns, with typically sub-nanosecond skew between ports on one unit, and very low skew between units.
  • Many SpaceWire test setups are small, and a single test unit with up to eight ports is adequate. But missions are envisaged with many tens or even hundreds of SpaceWire ports. Multiple 8-port units that can be used together, as if they were a single unit with many ports, is clearly good modular practice. 4Links not only supplies such capability, but also enables the time-tags of any number of units to be synchronized, to a resolution of 3ns, over a distance of up to 50 metres.
  • 4Links products enable measurement of the SpaceWire disconnection timeout. This has detected failures to meet even the wide tolerance permitted by the ECSS standard.
  • Test equipment needs to report not only IF something works but also how well it works. A key parameter of any SpaceWire design is how fast it can receive data, but test equipment from other suppliers has large gaps between the available transmit speeds and so offers little more than a go/no-go test of the SpaceWire receiver. 4Links products enable the user to adjust the test speed in increments of 1Mbit/s or less, so that the actual operational margins can be measured.

Customer and User Experience

All of these comments were volunteered; all suggest delight in using 4Links products.

  • `The most mature, most appropriate solution'
  • `You have established 4Links as THE supplier of quality SpaceWire test equipment'
  • `The beautiful 4Links box'
  • `The choice was obvious'
  • `We've had all sort of problems with our new equipment, but none at all with the 4Links test equipment'
  • `We've had all sorts of problems with the free-issue test equipment we were given, no problem at all with the 4Links. We want to buy more'
  • `This is just what SpaceWire needs, and no one else is anywhere close'
  • `We love these guys'