With more than a year under its belt since it was officially ratified by PICMG in March of 2011, CompactPCI Serial (PICMG CPCI-S.0) has proven to be a good example of how an industry standard can be upgraded to meet the needs of evolving computing parameters while protecting the historical investments tied to the original architecture. The fact that it has found a new home in a wider variety of application environments is just one more benefit that this new computing standard offers.
Although derived from the successful, modular CompactPCI standard, CompactPCI Serial is a standard all on its own that allows new embedded systems to be built using time-proven CompactPCI technology, yet incorporate the performance advantages of serial communications.
Fifteen years in the embedded computing industry is more than a lifetime for many components, technologies and systems that exist in this sphere. CompactPCI has been in existence for about that long, so change was inevitable. Fortunately for many embedded designers, this change was not in the form of a complete digression from the proven mechanics of the original, highly utilized standard (Figure 1).
Why Reinvent the Wheel?
The new age of CompactPCI Serial computing still accommodates 3U and 6U boards in IEC 1101-compatible 19" systems, ensuring the reliability of the CompactPCI bus interface well into the future, while meeting all the requirements of modern modular systems without the increased costs of other alternative standards.
And, the benefits of modernizing CompactPCI not only impact the system, but the designers themselves. Think about the knowledge base among the embedded design community and the number of individuals familiar with CompactPCI as a computing platform. When new standards are put forth, designers are often faced with having to throw away existing information and develop systems under tight time constraints and shrinking budgets, while learning a new technology platform and mounting the design hurdles that are inevitable.
Crucial questions begin to emerge. How much of the initial investment can be salvaged versus having to navigate through the re-architecting of an entire existing system? How much development time has been built into a project that is utilizing a new industry architecture, and are the expectations realistic to troubleshoot, integrate and deliver a functional platform?
Designers who have already integrated 3U and 6U CompactPCI boards into their system designs can easily utilize the increased functionality of CompactPCI Serial without the fear of adapting systems to a different standard. Appli cations where CompactPCI has been used effectively include image and data management and recording in surveillance systems, camera control systems for surveillance, different possibilities for integration of wireless communication, audio data processing, and computer simulation or a computer cluster in industrial quality control, to name a few.
And, CompactPCI Serial can now be applied in harsh and safety-critical environments in addition to the many markets mentioned above, as well as in areas with electronics in mobile applications, especially on rail and road, in ships and avionics, and research and development.
Bridge the Gap from Old to New
The thing that drove this new standard’s development — the fact that CompactPCI is so widely accepted and employed in embedded systems — also created a conundrum of how to maintain the investments already made in existing systems. Enter CompactPCI PlusIO (PICMG 2.30 — see sidebar), which defines the migration path from existing CompactPCI systems to one using only serial interfaces through CompactPCI Serial. With this hybrid standard, designers can migrate portions of a legacy system to serial technology as time and budgets allow. And the standalone CompactPCI Serial standard gives designers the flexibility to create completely new systems based on serial technologies.
Making the Serial Connection
CompactPCI Serial has been specifically developed around the familiar 19- inch technology, which mechanically speaking, allows both ‘old’ parallel boards and new serial boards to operate in ideal conditions, side by side, in the same chassis. But changes have been made to update the older CompactPCI to meet today’s high-speed computing requirements.
One of the most notable alterations is the incorporation of a high-speed connector (Figure 2) with a considerably higher signal density and faster transmission frequencies of up to 12 Gb/s, with less than 3% crosstalk.
So, while the dimensions of the backplanes, front panels and handles, as well as the well-proven hot plug mechanics of CompactPCI Serial are the same as those for CompactPCI, this more dense connector offers up to 184 pin pairs (368 pins) per 3U board and supports only modern point-to-point connections: up to 8 PCI Express, SATA, USB and Ethernet interfaces without a bridge.
The new codable connector resembles the old 2 mm type, but up to six connectors per 3U board can be used. And, with its own walls, it’s much more robust and protected against incorrect plug-in that causes damage.
The high-speed connector also saves significant costs as a component itself, as well as in system integration, since the architecture does not require a separate switch fabric infrastructure, greatly simplifying the implementation of CompactPCI Serial.
The connector also provides increased robustness to enhance system re liability. This opens up new CompactPCI Serial applications, including the harsh and mobile environments discussed above, increasing the target markets that can use systems based on this new, cost-effective standard.
Designing a Solid System
Regardless of their experience level working with legacy CompactPCI, system designers will need to define the parameters of a system being built to meet the needs of the specific application. Using CompactPCI Serial will pose a similar set of questions.
Considerations need to be made to determine which serial interconnect is the best to use: Ethernet for star and mesh architectures, SATA for RAID systems, USB for wireless connection, PCI Express for super-fast graphics, and so on.
The simple star topology used in CompactPCI Serial eliminates the need for bridges or switches in a system with up to nine slots, because the system slot supports up to eight peripheral slots. In principle all peripheral slots are identical. Only two are connected via extrawide PCI Express links (Fat Pipes), which can be used for high-end graphics extensions, for example.
The power supplies, fans and 19" racks used by CompactPCI Serial are COTS and the backplanes are either standard components with two to nine slots or are offered as hybrid backplanes (CompactPCI Serial — CompactPCI PlusIO — CompactPCI). System slot boards come with the latest Intel architecture or, in some cases, with PowerPC.
Mezzanine cards offer the flexibility for Ethernet mesh systems. Peripheral slot boards provide I/O variety: hard disk shuttles, XMC and PCI Express MiniCard carriers, USB, fiber optic and audio interfaces, Gigabit Ethernet interfaces and switches.
Modernizing Legacy CompactPCI Systems
By utilizing the existing, dependable mechanics of CompactPCI, CompactPCI Serial has proven to be a cost-effective, time-saving and modern technique for traditional industrial CompactPCI applications as well as newer rugged and mobile ones. This is not merely a case of defining a new standard just for the sake of calling it ‘new.’
CompactPCI Serial’s true value is starting to show as more products become available, leading to more system implementations in a wider variety of embedded computing applications. Because of this, the CompactPCI bus architecture can now provide the necessary technological updates for embedded system designs well into the future.