Why 4Links uses Ethernet in its SpaceWire products, rather than the PCI bus
You might have noticed that 4Links sells Ethernet-connected PCI SpaceWire interfaces, rather than PCI-connected ones. Why?
- PC backplanes change faster than spacecraft project lifecycles, so a PCI test interface might not be compatible with your new PC equipment by the end of your project! Do you remember ISA, MCA, PCI, PCI Express? What next??
- Laptop computers do not have PCI bus slots. We would not want to prevent our customers from using portable test equipment that is controlled by laptops.
- PCI device drivers would have to be written for every combination of processor architecture and operating system, which would be a nightmare for us to support. Instead, we supply a C programming API for Ethernet connections to our products. Ethernet is available on virtually every host computer and the operating system providers optimise their Ethernet device drivers, so we don't have to.
- Ethernet allows the test computer to be placed much further away from the SpaceWire system-under-test than PCI does. This enables remote testing strategies that should reduce travel costs and increase the flexibility of testing schedules.
- Ethernet allows different test engineers to access the SpaceWire system using their own PCs, rather than having to use a central one with its PCI SpaceWire interface.
- 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 computer using a PCI card.
- Ethernet is a network-centric technology, and is thus more appropriate to SpaceWire communications than a computer-centric PCI interconnect.