Faced with an EOL issue, more and more engineers are basing their replacement systems on modern Ethernet I/O products, connected to new, off-the-shelf computers.

Ethernet I/O products from United Electronic Industries (UEI) are only a few years old and are based upon up to date modern technology. In addition, UEI has a track record for maintaining production of products and not forcing our customers to upgrade to the latest, greatest technology until they want to, not need to.

Indeed, product obsolescence is often not the primary reason a VME designer switches to an Ethernet solution. Sometimes the designer simply needs a feature or capability not available on a VME platform. UEI Cubes and RACKtangles have a number of advantages relative to VME systems.

The UEI Cube and RACKTangle allow designers to pack more I/O into a smaller space than VME racks. A DNA-PPC8 Cube measures just 4.0 x 4.1 x 5.8 in., and yet allows the installation of up to 150 A/D channels, 192 D/A channels, 288 DIO points, 72 ARINC 429 channels, 48 serial ports, 48 counter/timer/quadrature channels or 24 CAN-bus ports. The 12-slot RACKtangle I/O chassis provides double these quantities in a standard 3U rack form factor.

Using the UEI high density chassis, designers have found they no longer need to mount their I/O in remote racks and then run long cables between the I/O rack and the main “product” (e.g. a simulator, a dynamometer, a test stand, etc.). Mounting the I/O right on the product decreases noise pick up in the signal wiring and reduces the cost and complexity of running hundreds and sometimes thousands of wires between the sensors and a remote I/O rack. With the I/O mounted locally, installing a product at a customer or final installation site is as simple as connecting power and Ethernet.

Customers who take advantage of the Programmable Automation Controller versions of UEI’s I/O also eliminate the space required by an external host computer. The UEIPAC builds a standard Linux based operating system directly into the I/O chassis, allowing the units to run full stand-alone.

Flexibility comes both from the unique Cube/RACKtangle form factor and from the array of different I/O boards that may be installed in a UEI Ethernet Chassis. With I/O Cubes as small as 4 x 4.1 x 4 in., designers can put a UEI chassis in places a VME rack would likely never be considered. The UEI I/O Cube is rated from -40° to 85°C, 50 g shock, 5 g vibration, 0 to 70,000 ft altitude and has been radiation tested for space applications. A fibre optic interface allows the I/O system to be mounted up to 20 km from the host computer.

As for I/O flexibility, UEI offers over 30 different boards. In addition to standard analog and digital I/O, there are CAN-bus, RS-232/422/485, ARINC-429, quadrature encoder inputs and soon there will even be a MIL-STD-1553 board.

Like most I/O manufacturers, UEI offers support for popular Windows development languages and applications. Unlike many I/O vendors, UEI also provides factory written drivers for all popular Linux and Real-Time operating systems including QNX, RT Linux, Windows RTX, RTAI Linux and more.

Does Ethernet I/O offer the performance available on the VME platform? The answer is a resounding yes. UEI’s patented DMAP Ethernet protocol ensures systems with thousands of I/O points are monitored and updated, all in less than a millisecond.

If you’re building your first system, you don’t want to wait 6 to 12 weeks to get a piece of hardware to evaluate. If you’re releasing your project to production, you don’t want to hear from purchasing that the component you need is 12 to 16 weeks away. Finally, if your up-and-running system takes a lightning hit, you don’t want to find out a replacement board is two months away. All of UEI’s Cube and RACKtangle I/O products mentioned above are standard, off-the-shelf products.

This article was excerpted from the United Electronic Industries application note #027, Ethernet I/O Chassis - A VME Alternative.
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