Topic Number N03-023
Phase II

Simulator systems require a large volume of input and output (I/O) signals in a variety of signal formats.  Operator switches and knobs can generally be handled by straightforward digital I/O.  More complex devices such as pressure sensitive joysticks and other variable controls require precision analog to digital (A/D), or digital to analog (D/A) signal conversion to provide accurate simulation.  Additionally, cockpit instruments such as multi-function displays (MFDs) or other complex devices which require control data streams in standard protocol formats (ARINC standard busses, MIL-STD-1553, etc.), or system unique formats (manufacturer defined protocol on HotLinkTM, LVDS, TMDS, etc.) must also be accommodated.

Traditional simulator data input / output systems have consisted of a myriad of I/O devices, often using manufacturer unique hardware and software (ASTTM, MSTTM, Adapted Ethernet, etc.), tailored to a solution for each device.  On larger simulator platforms, the I/O systems often require large racks of electronics, which are not suitable for remote location near the operator control or device to which they interface, requiring bundles of cables from one location to another.  On motion based simulators, this often creates high initial and maintenance costs to be incurred.

With smaller simulator devices, adapted PC based technology has often been utilized.  These systems generally consist of I/O cards (COTS or custom) inserted in open expansion slots within a PC chassis, again requiring cables from a fairly large chassis to the operator interface device.  Additionally, most of the available COTS I/O devices require specific cable types (such as high density ribbon cable) for their interface, making breakout mechanisms (such as custom cable assemblies) a requirement to route signals to their intended destinations.

As packaging technology for consumer PC devices has become very cost conscious, driving down the PC manufacturing costs has become essential to survival in that market.  As with the PC itself, packaging costs of PC peripherals has also become a cost driven market, requiring smart devices that connect to PCs to become less expensive to manufacture.  With this goal in mind, one essential serial bus technology has evolved and taken root in the market: the Universal Serial Bus (USB).  USB provides the type of flexibility required to support a complex I/O system often required by simulation systems.

With USB2.0 supporting a bit rate of 480 Mb/sec data rates, large volumes of data can be moved from a host platform to its peripherals.  Most commercially available PCs now offer multiple USB 2.0 busses; it is very common to find as many as 8 USB 2.0 ports as standard equipment.  PC integrated circuit manufacturers have directly incorporated the USB interfaces in the bridge chip sets that connect the processor local bus to the outside world (referred to as the North Bridge device in a typical PC architecture).  

Key to any solution to a low cost, simulator I/O platform is the use of high speed serial bus technology, and flexibility of the peripheral for the large variety of I/O needs. 

When coupled together, the low cost bus controller and programmable logic device (PLD) create an extremely adaptable I/O solution.  For purposes of this proposal, the PLD acronym will also include their larger cousin, the Field Programmable Gate Array (FPGA).  Taking advantage of both of these new technologies can yield fully programmable, compact, inexpensive I/O devices that have the ability to handle both simple digital I/O as well as complex data streams.  Localized processing can be shared between the interface controller, and the PLD.  PLDs of adequate size can perform signal processing functions of data in real-time, or simply provide a data path for variables to / from the host system.|