Product Focus: Databus

One of the biggest drivers for new generation databus technology is the transmission of video, images and other visual information — such as for terrain awareness and mapping, as well as weather radar — which requires large increases in data quantity and refresh rates.

Manufacturers of systems that address high bandwidth databus networking face a number of challenges. These include maintaining the reliability and robustness proven in lower bandwidth networking technology, while at the same time keeping the cost and power requirements in the same range. In addition, higher bandwidth applications typically generate more data and put pressure on downstream technology such as storage (which requires more memory) and off-aircraft data links (which have to operate at high speeds).

Another challenge relates to the cost and viability of trying to route new high-speed data buses to multiple points within the aircraft. Both military and commercial environments are typically noisy and rife with various types of interferers that may cause dramatic effects on the integrity of the data on the network. Ensuring a high degree of integrity and determinism must be built into the network design from the ground up.

Distributed Architecture

“What we are seeing as a continuing trend in the commercial aircraft industry is the movement toward a more distributed control architecture,” said Christopher Stabile, marketing communications manager with Data Device Corp. (DDC), of Bohemia, N.Y. He referred specifically to the Airbus selection of Mil-Std-1553 databus technology on its under-development A350XWB.

Flight control, for example, was always accomplished with centralized processing from a flight control computer (usually an array of redundant computers), which would be employed to control actuators. The actuators were basically very simple devices, where the central flight computer would implement and manage all aspects of the control loop. The actuator was just an actuator and had no processing power.

What is happening today, with the A350 being one of the commercial aircraft leading the way, is the distribution in implementation of these control laws. The central flight computer will still do the top-level implementation of the flight control function, but now intelligent actuators with a processor contained within will implement its part of the control loop. Rather than having one central processor that does everything, the actuators can start to take high level commands and handle some of the local control.

“The advantage has to do with redundancies and safety,” said Stabile. “You can get tighter control loops because you are not going end-to-end in terms of how you are processing; you are splitting that power up. What you want is a more efficient system where you have less processing power within the flight control computer because it is distributing to multiple elements, while it is done in such a way that you have a lot of inherent redundancy for safety aspects.”

With such a distributed architecture, there is also created a need for the flight control computer to communicate with these intelligent actuators. That is something that didn’t exist in previous systems, and creates a challenge for designers because they need to develop something that is very reliable, deterministic, fault tolerant and with a low bit error rate in terms of timing within the various control loops.

“These are all things that Mil-Std-1553 brings to the table,” said Stabile. “So you see emerging applications on commercial aircraft that need a robust deterministic databus for applications that didn’t use it before. Airbus was one of the first to recognize that 1553, even though a fairly old technology, is still commercially viable and one of the best solutions out there. We are seeing a lot of interest from other manufacturers in 1553, and a lot has to do with Airbus’ initial selection. The other part is the evolution of systems, and the movement toward distributed architecture in critical systems like flight controls.

“If you look at an A350, you don’t have a homogenous network across the aircraft. What you end up doing is partitioning the network based on functional need. The network that streams video to a seatback TV screen is different than the network used to control the flight control systems or the engine. When they start looking at these systems, they look at them independently. With flight controls, for example, it is not a high-data-rate application because it is a series of very small commands being sent through a tight loop. What is interesting is that even though 1553 is not as fast as some newer technology, it is more than fast enough for some of these emerging applications.”

Such a distributed architecture also needs a backbone network to be effective. ARINC 664, sometimes called AFDX (Avionics Full-Duplex Switched Ethernet), used on both Airbus and Boeing aircraft, is trending in the last few years as the high-speed network of choice to basically tie all the systems together and provide the backbone for sharing data between each of these independent systems.

Meanwhile, Edgewater Computer Systems of Ottawa continues to mature its Extended 1553 (E1553) databus technology into reduced size and power solutions, and is working to expand market interest in places like Europe and Asia.

“Internationally, an effort is now well underway to ensure that the technology is standardized by a recognized standards body,” said Greg Fielding, Edgewater vice president of marketing. “Standardization remains a high priority in order to ensure interoperability and compatibility among multiple potential sources of supply.”

To expand its reach, Edgewater plans to release an Extended 1553 PCI Mezzanine Card (PMC) and a next generation Evaluation Kit (EVK) integrated with the PMC for customer integration, characterization and test activities.

Edgewater had initially focused in the last few years on very high-speed data rates of 100 to 200 Mbps, though its efforts today fall into an area of speeds down at the 1 to 5 Mbps level. That is a data rate at an intersection where older civil and military aircraft without high-speed data bus capabilities can potentially be upgraded to take advantage of data-rich applications.

Operators of these aging aircraft continually face the choice of purchasing new aircraft or retrofitting older aircraft with new equipment. This is particularly true with military or quasi-military fleets such as those operated by the Coast Guard or other organizations that fly aging C-130s, for example that are decades old.

For those operators, the attraction of adding new electronics in the form of weather radar, flat-panel displays, advanced GPS and terrain-warning systems is strong, but seemingly not possible. The problem is compounded due to the fact that military aircraft electronics often communicate via the Mil-Std-1553B databus standard, while much of commercial electronics use the ARINC 429 standard.

“A flexible, COTS (commercial off-the-shelf) solution to the problem of converting Mil-Std-1553B data to the ARINC 429 standard and vice-versa can provide system integrators with a low-cost method of adding new electronics to older aircraft,” said David Garcia, vice president of marketing and sales with AgiLynx Inc., of Billerica, Mass.

Other companies, including Ballard Technology, Everett, Wash., and YED, of Bristol, U.K., have recently developed airborne protocol converter units to convert the 1553 standard to ARINC 429. Their units have been tested to environmental standards such as RTCA DO-160, which can be cross-referenced to older military standards, and have been proven to operate in airborne environments.

“The problem is to come up with a product that meets almost everyone’s needs as a COTS solution, which is quite the challenge given the variety of parameters and data formats found on aircraft databuses,” said Garcia.

The general approach is to provide a variety of I/O options, with software configurability to handle the detailed conversion needs. AgiLynx’s approach is to perform the configuration process on a desktop computer with a point-and-click application that downloads the configuration details into the converter without affecting the DO-178B certification of the software in the unit.

“We faced the challenge of creating a configuration file that can be considered an input to the COTS unit, and then creating a verification test suite that completely tests the range of possible configuration file inputs, in order to allow our customers the ability to configure their units without writing or verifying new software,” said Garcia.

Other Trends

There are a number of additional trends in the databus world, specifically around 1553 that have held strong for the past several years.

One is the incorporation of what used to be two separate devices into one package. Designing a 1553 interface has typically meant the need for one electronic device containing the integrated circuits and the other consisting of a transformer. Some manufacturers are now combining the two devices into one integrated package for less weight and better performance.

Another design trend related to 1553 interfaces is away from companies using FPGA solutions with an IP core of some sort, with the idea being that a company takes the function and incorporates it into their own FPGA, which is then used to implement the 1553 interface.

“What we have seen is the interest in IP-based solutions has declined dramatically,” said Stabile. “Instead of designing their own boards to do it, or implementing some sort of custom or semi-custom solution, people are buying complete board solutions.

“Many companies are becoming more of an integrator and less of a custom hardware developer. Everybody used to design their own custom boards, especially since the military was all about custom solutions. What has changed over the years is now commercial off-the-shelf systems have taken off to the point where people are looking at standard form factor boards like PMC mezzanine cards. Companies are putting together pieces rather than developing them from scratch.”

Avionics Magazine’s Product Focus is a monthly feature that examines some of the latest trends in different market segments of the avionics industry. It does not represent a comprehensive survey of all companies and products in these markets.

Market Moves

Following are developments announced by manufacturers of aerospace databus products.

âž¤ Ballard Technology, based in Everett, Wash., in September announced the availability of an optional orange case for its line of pocket-sized USB Avionics Databus Interfaces. The case allows it to be clearly seen and identified as test equipment for removal from an aircraft prior to its return to service after maintenance and support operations, the company said. The standard case color is black. The USB interfaces enable engineers and technicians to test, simulate and analyze Mil-Std-1553, ARINC 429 and ARINC 717 avionics databuses using a PC.

âž¤ Vector Aerospace, of Stuttgart, Germany, in September said it had added ARINC 810, 812, 825 and 826 support to its development and test tools, CANoe.CANaerospace 7.2. Vector said the latest version of CANoe.CANaerospace and CANalyzer.CANaerospace contain functions for networking with ARINC protocols and the CANaerospace protocol, allowing developers to use these functions for creating simulations and analyzing and stimulating bus traffic.

âž¤ Holt Integrated Circuits, Mission Viejo, Calif., released several new databus products in 2010, including an ARINC 429 line driver powered by a +5V supply, the HI-8592.

The company also introduced HI-8448PCx, calling it the world’s smallest octal ARINC 429 line receiver. Each receiver channel will translate incoming ARINC 429 signals to TTL/CMOS compatible digital outputs. The devices operate from either a 5V or 3.3V supply and have a common mode capability of +/- 5V with respect to ground.

âž¤ AIM GmbH, of Freiburg, Germany, in October introduced a family of USB-based products for laboratory, field test and data loading applications. The APU429-x and APU1553-x modules are implemented in shirt-pocket sized boxes, which can connect to various types of computer systems via USB ports. “USB2.0 connections are available on almost any computer system, so test engineers no longer have to dedicate a host platform for their ARINC 429 or Mil-Std-1553 requirements by using our APU429-x/ APU1553-x modules,” said Marco Maier, lead hardware design engineer for the company’s USB-based module family.

Also in October, AIM released a PCI-ExpressCard system for Mil-Std-1553 testing. The AEC1553-x integrates 1 or 2 dual redundant Mil-Std-1553 A/B bus streams on one ExpressCard.

âž¤ In March, Excalibur Systems, of Elmont, N.Y., introduced the EXC-664PCIe board, an ARINC 664 test and simulation board designed to help integrate avionics suites, and can simulate up to two AFDX end systems with full dual redundant support for receive and transmit operation. The board contains room for two standard 4000 modules that can support multiple channels of other avionics communications protocols including Mil-Std-1553, ARINC 429, Serial, Discrete, ARINC 708 and CANbus.

âž¤ API Technologies Corp., based in Ronkonkoma, N.Y., in October received a $1 million order for its National Hybrid Mil-Std-1553 transceivers. The company said the order will be used by “a Fortune 50 company in its line of military avionics equipment.”

In July, API Technologies introduced the NHi-1565 SOIC, a hermetically sealed ceramic Dual 1553 Data Bus Transceiver to its National Hybrid product line. The NHi-1565 SOIC comes in a standard 5V or a low voltage 3.3V version. It measures 0.275 by 0.505 by 0.095 inches, and is available in a temperature range of -55°C to +125°C.

âž¤ GE Intelligent Platforms, Charlottesville, Va., in March released version 7 of its BusTools-1553 Bus Analyzer software application, designed for analyzing, testing and simulating data traffic on the 1553 bus. “The avionics market is moving away from character-based bus analyzers in favor of more intuitive, GUI-based solutions that are much easier to use,” said Ben Daniel, GE Intelligent Platforms business manager for avionics. “With the BusTools-1553 version 7 announcement, our spirit of partnership sees us making available a capability that has been much requested by our customers that will allow them to transition to future hardware platforms with minimal effort and expense.”

âž¤ Beta Transformer Technology Corp., Bohemia, N.Y., a subsidiary of Data Device Corp., introduced the BXC-A-2 two-stub box coupler, which achieves full Mil-Std-1553 compatibility. The company said it is ideal for system development, lab, test and flight line applications.

âž¤ Sital Technology, Kfar-Saba, Israel, in October received a formal approval from the U.S. Patent and Trademark Office for its “Tails-Code-Key” technology, a method for detecting a fault in a bus network. The company said Tails-Code-Key does not interfere with activity on the bus, and therefore can be used for detecting problems during normal operation.

“This is a major breakthrough in avionics, cars and other systems maintenance and reliability,” said Ofer Hofman, founder of Sital.

In June, the company released Minuet, a family of compact, standalone, Mil-Std-1553B protocol terminals, which include Bus Controller, Remote Terminal and Monitor.