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Divergent Advantages of 1553 and Etherent form Fruitful Marriage

Bus interfaces such as 1553 continue to live on as preferred technologies for avionics. Highly integrated products are providing bridging to link legacy I/O to modern computing interconnects like Ethernet and USB.


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The expression "if it works don't fix it" seems to apply the MIL-STD-1553 bus interface more than any other technology used in the defense and avionics. With over three decades of use flight and mission-critical systems aboard military aircraft, the 1553 is entrenched on both older planes and new aircraft like the F-35. By modern standards, the bandwidth of 1553 makes it seem an ancient relic. But for what it needs to it's just enough for the command and control functionality to fly an aircraft. In many ways 1553 fits nicely into the kinds of requirements of today's budget constrained environment.

According to Greg Tiedemann, Product Line Director at Data Device Corp., there's both technical and business reasons why 1553 continues to thrive. On the technical side it's considered good enough. It's also extremely well proven with probably millions of flight hours on 1553-based aircraft all over the world. There's nothing as ubiquitous except for Ethernet, but standard Etherent isn't something you can fly a plane with because it lacks the determinism and reliability inherent to 1553. In the past ten years there's been some enhanced Ethernet interfaces developed like AFDX and proprietary schemes like time-triggered Ethernet, but none of seen any widespread adoption.

On the business side, 1553 remains the top choice simply because there's been little justification to create and adoption any replacement protocol for it. If there were several new military aircraft platforms in the works, there would perhaps be motivation to create a new bus architecture-or adopt an existing one like AFDX-for those platforms. In reality such new platforms don't exist and aren't in the budget plans of the DoD. The focus is instead on taking legacy platforms and extending their life while adding new functionality to them.

Solutions for Bridging

With all that in mind, vendors are rolling out bridging and conversion solutions that link legacy technologies such as 1553 to the much faster Gbit and 10 Gbit Ethernet interconnects. Meanwhile, today's level of semiconductor integration means the idea of a 1553-only board is outdated. It's easy to combine 1553 with other board or box-level functions. Those trends have matured to include intelligent (processor based) multi-protocol solutions that link different protocol schemes.

Exemplifying the trend toward highly integrated solutions, Data Device Corp. in March introduced its BU-67125W Compact Avionics Interface Computer (AIC-RC) (Figure 1), offering a completely customizable, off-the-shelf solution. The AIC-RC combines Intel's embedded Atom computing architecture, with DDC's avionics data networking expertise and custom I/O capabilities, to deliver avionics connectivity computing in a small form factor, deployable, rugged enclosure. The system is qualified for rugged air and ground environments. It is expandable using mPCIe and I/O expansion modules to support a wide range of I/Os. Custom front panel connector configurations support unique deployed I/O requirements. In Remote Access mode the unit allows easy access to 1553/429 connection via Ethernet network. And in Protocol Conversion mode it allows users to create embedded software that seamlessly transfers data between 1553, 429 and Ethernet interfaces.

Figure 1
The BU-67125W Compact Avionics Interface Computer (AIC-RC) combines Atom processor with mPCIe and I/O expansion modules to support between 1553, 429, Ethernet and more.

Portable USB-1553 Link

USB is another interface technology system developers are using to link with 1553. In May AIM-USA launched its ASC1553 product which offers a USB based interface solution operating with a single USB2.0 port (or higher). The low power hardware design offers a half-pocket sized dual redundant interface for MIL-STD-1553. This saves valuable power on battery powered hosting platforms and gives users longer operational time without requiring an external power supply or a battery re-charge.

While portable USB based interfaces for MIL-STD-1553 testing have been on the market for a number of years, this one uses AIM's SmartCable approach. The key benefits of the SmartCable are its lightweight, portable and low power design, all complimented with a full function, dual redundant MIL-STD-1553 interface. Avionics test engineers are able to debug, monitor, record and even playback MIL-STD-1553 bus traffic for troubleshooting and bus analysis purposes.

Data bus protocol-related real-time capabilities over the USB interface are dealt with by having the necessary hardware, firmware and processing resources directly integrated within the almost standard D-Sub connector sized housing. Additional processing capability is offered by the use of a dual processor System-On-Chip (SOC) device inside the ASC1553.  The ASC1553-A provides a dual redundant MIL-STD-1553 interface with concurrent Bus Controller, Multiple RT Simulator (31) with a Mailbox and Chronological Monitor functions. An optional Auxiliary I/O connector gives access to 8 (avionic level) General Purpose Discrete I/O signals and 1 trigger input and 1 trigger output, plus an IRIG-B time Encoder/Decoder providing a sinusoidal input/output and 'freewheeling' mode incorporated. The SOC of the AIM SmartCable has access to 128MB of Global RAM and boot up flash memory.

Product variants of the ASC1553 include the single function and simulator only versions which offer cost savings compared to the full function version. For pure MIL-STD-1553 only applications, the model ASC1553 is available without the optional Auxiliary I/O interface (IRIG-B, Discrete and Trigger I/O). The ASC1553-A and ASC1553 SmartCables are API compatible to the existing AIM MIL-STD-1553 product portfolio and support an easy migration of applications from the AIM APU1553-1 predecessor USB interface.

1553 Aboard Landing Craft

Although 1553 is most often associated with aircraft and avionics, it's found use in a host of ground and shipboard systems. For example, earlier this month United Electronic Industries (UEI) announced that the US NAVY selected its DNR-MIL series I/O control chassis in conjunction with its VxWorks BSP as the new Command, Control, Computers, Communication and Navigation (C4N) SBC4 Control, Alarm and Monitoring System (CAMS) for the Landing Craft Air Cushion (LCAC) fleet.

Based on a robust PowerPC processor, running VxWorks with fully redundant Ethernet connectivity to the boat's host computer, the UEI system replaces the previous controller, and provides a much smaller, easier to maintain and more reliable solution. I/O provided by the CAMS unit includes analog input and output, digital I/O, 16 serial ports and MIL-STD-1553 all connected through standard military style 38999 connectors. Key to the Navy's decision to select UEI's DNR-MIL was it met the required MIL-STD-810 and -461 environmental specifications, according to UEI.

1553 on CompactPCI SBC

One popular way to implement 1553 is as an integrated embedded SBC function. While North Atlantic Industries (NAI) makes a number of products that include 1553, one of its latest offerings is the 75PPC1-FT3-AR1 (Figure 2). The board is powered by NXP's 1.2 GHz Quad QorIQ P2041 PowerPC processor, and is configured with quad channel, dual redundant, MIL-STD-1553B, and 12-channel ARINC 429/575 Tx/Rx communications bus ports. The board includes a MIL-STD-1553B - (FT3) quad-channel, dual redundant, balanced-line physical layer; a (differential) network interface; time division multiplexing; half-duplex command/response protocol, and up to 31 remote terminals per channel designed for use with rugged and commercial avionics applications. Also provided is ARINC 429/575 in up to twelve programmable Rx/Tx channels. This provides essential air-data information for displays, autopilots, and other flight controls and instrumentation on commercial and military aircraft.

Figure 2
The 75PPC1-FT3-AR1 SBC sports a 1.2 GHz Quad QorIQ P2041 PowerPC and is configured with quad channel, dual redundant, 1553B, and 12-channel ARINC 429/575 Tx/Rx communications bus ports.

Aside from 1553, ARINC 429 is an interface standard that continues to enjoy widespread use. In keeping with the trend toward highly compact solutions is the webFB Wireless Electronic Flight Bag from Astronics (Figure 3). The ultra-compact webFB easily fits in the palm of the hand, yet incorporates the capabilities of both an AID and a wireless server. The built-in AID safely gathers essential data from the aircraft's ARINC 429 and 717 databuses and conveys it to custom software or EFB apps hosted on the internal server. Using a wireless connection to portable EFB tablets, the webFB securely delivers this valuable information right to the fingertips of the flight crew.

Figure 3
The webFB Wireless Electronic Flight Bag easily fits in the palm of the hand. It safely gathers essential data from the aircraft's ARINC 429 and 717 databuses and conveys it to custom software or EFB apps hosted on the internal server.

In May Astronics announced receiving a Supplemental Type Certificate (STC) and Parts Manufacturing Approval (PMA) for webFB for use on Boeing 737 aircraft. This approval represents the first time a wireless Aircraft Interface Device (AID) has been certified for use in the flight deck by the Federal Aviation Administration (FAA). Astronics' software partners are currently developing a variety of enhanced EFB applications for the webFB that are focused on increased operational efficiencies including fuel and time savings, electronic tech logs and real time QAR monitoring and event notifications. For software vendors, the webFB provides a rapid and practical solution for developing applications and deploying them into the flight deck and beyond. Along with the webFB, the STC also approves the installation of the Astronics EmPower system in the flight deck with USB outlets for charging portable EFBs while in flight. Also available are several choices of ARINC 828 compliant fixed EFB mounts.

Trevose, PA
(267) 982-2600

Ballard Technology

Everett, WA
(425) 339-0281

Chesapeake, VA
(757) 366-9211

Data Bus Products
Manhasset, NY
(516) 365-3946

Data Device Corp.
Bohemia, NY
(631) 567-5600

North Atlantic Industries
Bohemia, NY
(631) 567-1100

United Electronic Industries
Walpole, MA
(508) 921-4600