Choose Smaller When VME Slot Cards Won’t Fit into Military, First Responder Vehicles
VME isn’t the ideal choice for small, low-cost, rugged systems. Sometimes other small form factors—such as COM Express®—are a better fit.
Ever since the COTS defense initiative was well established, VME has reigned supreme in deployed systems for military vehicles. VME was followed by CompactPCI, and now OpenVPX, slot card-based systems well suited to meet all the harsh environment specs. But as technology and cost pressures force size reduction, other standards-based solutions have become more viable for smaller platforms better suited to mobile environments.
We’ll examine how Elma created a very low cost “Rugged Vehicular System” using off-the-shelf COM Express, mini-PCIe, and an expandable I/O carrier board. As expected, the box-level system meets many MIL-SPECs, and operates over -40°C to +71°C. Equally important is how Elma brought together multiple COTS companies—including ADLINK—to create the purpose-built box.
In the Beginning…
The company also doesn’t mandate one particular CPU, with eight (8) different Intel CPUs available . Flavors range from Intel® Celeron®, Intel® Core™ i3, Intel® Core™ i5, all the way up to 4th Generation Intel® Core™ i7 (Haswell) processors. Elma chose the Intel® Core™ i5-4400E 2.7 GHz CPU for the ComSys-5001. The chipset is Intel’s QM87 Express, which offers more I/O than Elma needs. For example, on ADLINK’s module, there are eight (8) USB ports (4x 3.0 and 4x 2.0); Elma only brings four (4) of them out on the ComSys-5001.
Among the reasons Elma chose ADLINK was the ability to guarantee -40°C to +71°C for their rugged chassis; inside the box cards run hotter and ADLINK can guarantee operation at +85°C. Another advantage of ADLINK’s SBC is evident in Figure 4: clean design. Notice how much space is available around the largest (and hottest) components. This makes adding a heat spreader and thermal pads easier than if the board was more tightly designed with little space between components. Interestingly, ADLINK offers a heat spreader for the Express-HL, but Elma chose to design its own.
IEEE 1101.2 conduction-cooled slot cards with wedgelocks, integrated 100W heatframes, and backplane I/O remain the choice for deployed, ultra-rugged vetronics, avionics, shipboard and space-based systems. But what if all you need is a powerful SBC in a rugged “shoebox”, common I/O with wireless connectivity, and some pre-planned product improvement (P3I) upgradeability? According to Elma’s strategic marketing manager Valerie Andrew, “not all rugged systems program managers talk about LRUs.” Increasingly, she says, rugged environment clients “just need a solution that works.”
Of course, there are few companies more credible than Elma when it comes to high performance, often complicated, and extremely rugged conduction-cooled VME/VPX backplanes and ATR-style chassis. Yet even Elma recognized an opportunity for an “application-ready” shoebox (chassis) with good functionality at a reasonable price.
The result was the ComSys-5001 (communications system) that this author first saw displayed in January 2015 at an ADLINK partner event (Figure 1). What piqued my interest at the time was the box:
- appeared to be Elma’s first-ever complete, ready-to-go system.
- included Cisco’s IOS software with Mobile Ready Net IP routing. Essentially: the box could function as a low-cost, mobile router.
- contained an ADLINK COM Express computer-on-module and other cards, not VME!
Designed for a Market, Not a Program
It turns out that the Elma ComSys is indeed the company’s very first entry into pre-packaged systems. “It was designed for a market, not a program,” says Steve Gudknecht, Elma’s small form factor product manager. It has the look and feel of a MIL-SPEC box, right down to the (customizable) 38999-style front panel connectors. Current versions of the box are machined, but will later be made from extruded alloy to save cost in production volumes.
At under eight (8) pounds, the box is only 3.5 x 9.5 x 6.9 (inches, HxWxD) and contains no fans. Total power dissipation is near 50W, depending upon I/O options added via mini-PCI express cards. This means the box is completely passively cooled through a combination of radiated convection via the fins, and some conductive transfer through the bottom of the box. More interestingly, Elma’s product manager Gudknecht assures me that the inside electronics will operate within their respective temperature specs even when the box is operated in a 71°C environment.
Since there are no formal specs for conduction-cooled Type 6 COM Express boards (such as ADLINK’s Express-HL module)—nor for mini-PCI Express I/O modules—the magic of this rugged shoebox is how Elma managed to stuff the guts inside, keep the cost low, and meet the environmental specs. It took a balance of electrical, mechanical, thermal and product engineering.
What’s Inside the Box
Per Elma’s datasheet for the ComSys-5001, the chassis is a “high performance mission compute platform ideal for vehicular applications” in defense, first responder, mining and other rugged, outdoors market segments. The system uses a 4th Generation Intel® Core™ i5-4400E 2.7 GHz CPU on ADLINK’s Express-HL COM Express Type 6 module. ADLINK and Elma have worked together before, so choosing ADLINK as a supplier for Elma’s first systems product was a critical decision. (See sidebar: COM Flexibility is “Expressly” Available).
Also included is Cisco’s IOS software for network routing via Cisco’s Mobile Ready Net IP. A comprehensive package that takes an enterprise-class router and brings it out onto the (battle)field, Cisco’s software has been successfully deployed by other COTS companies and large DoD primes. It’s a proven commodity and highly desired for mobile networks.
The base configuration of the system includes most of the I/O on ADLINK’s module brought to the front panel, plus CANbus for intra-vehicular comms and Wi-Fi 802.11 a/b/g/n—hence the antennas in Figure 1. A block diagram for the ComSys-5001 is shown in Figure 2. Of significance is the number of PCIe lanes available from the ADLINK module, allowing modularity to two mini-PCI Express boards and a full-size XMC site for VME/VPX-style I/O. Clearly, Elma hasn’t forgotten its really-rugged slotcard LRU roots.
With 3U and 6U VME, VPX and CPCI slotcards, cooling is a well-understood process. Convection-cooled cards are cooled with moving air (fans), and conduction-cooled cards use heat spreaders and wedgelocks. Elma is expert in these areas and applied lessons learned to the ComSys-5001.
Exact details describing the complete card assembly and cooling techniques are considered company secret. However, product manager Gudknecht provides a vague explanation. The stack-up relies on a system of heat spreaders that “fanout the heat to the chassis sides and bottom.” A heat spreader is attached to the ADLINK module that mounts backside down into the chassis.
Next is the Elma-designed carrier board, much larger than the COM Express module and designed to accept two mini PCI Express add-in boards plus a PMC/XMC site for additional I/O. Attached to the backside of the carrier board is a series of cold plates and thermal pads, which favor the hottest I/O components. The box also provides mounting for dual MO-297 solid-state storage drives.
Finally at the top, an optional PMC/XMC module can be added for even more I/O. This is an impressive collection of modularity in such a small, fanless box. Elma describes the system as “configurable and mission evolution-proof.” We agree.
A System Marriage of Convenience
The system engineering that makes this box-plus-module assembly work together is impressive. The choice of Intel-based processors (instead of PowerPC or ARM, for example) was a market requirement, says strategic marketing manager Andrew. “Ten years ago, you’d see a PowerPC with an RTOS in this kind of system.” And it would be VME.
Today, Intel’s CPUs are preferred and allow “ramp up or ramp down” depending on performance needs. As seen on ADLINK’s datasheet, processor choices abound. But why ADLINK, instead of one of the many other small form factor vendors? ADLINK is seen as being “on the cutting edge of the latest processors,” says Gudknecht, The company offers lots of product choice, wide temperature range, and they even offer PC/104 modules which could potentially be used in a redesign, depending upon the options needed in future versions of the ComSys-5001 (Figure 3).
This article is sponsored by ADLINK Technology.