David Koppel

What is the difference between a standard I/O adaptor, such as, Ethernet or Canbus and an avionics adaptor?

Ethernet is the most used network protocol in the world with billions of connected devices. CANbus has been used in cars since 1991. Both of these very established protocols have been adapted to work with avionics.

What is the difference between a standard I/O adaptor for any of these specifications and an avionics adaptor?

For one thing the price, because they are so ubiquitous Ethernet and some CANbus adaptors can be had for a few tens of dollars whereas Avionics adaptors can cost in the thousands. Of course, the price difference is indicative of larger underlying difference. Let’s look at a few of these differences.

Standard adaptors are given data from a host and transmit the data over the bus. They don’t schedule it, they don’t remember it, they just ship it out. A great deal of avionics data is repetitive; altitude, latitude, roll, speed etc., are all constantly updating and need to be transmitted periodically. Using a standard adaptor would require the host to constantly do the updating at a cost of CPU processing time and – much more expensively – engineering time. Avionics adaptors usually have built in schedulers that handle all the timing issues; the host only needs update the data when it changes.

On the receive side, avionics adaptors provide timetags accurate to a few microseconds and often provide multiple storage options which can be used to handle different kinds of data, again simplifying the host computers task and reducing its workload.

In addition, the AFDX version of Ethernet and the ARINC 825 version of CANbus added many additional requirements – such as redundancy, complex scheduling and priority management that are impractical to handle on the host. Handling these requirements in the adaptor saves a steep learning curve in addition to many costly lines of code.

For Ethernet and Serial modules, our free Simulation Laboratory utility enables you to create scheduled transmissions without programming. It also displays data in engineering units based on definitions you provide via an Excel spreadsheet. NMEA packets are recognized and properly displayed. Exalt, our premium GUI tool, let’s you use graphics to input and display engineering data and even create engineering units (EUs) not actually on the aircraft by combining multiple EUs together.

Other utilities can be used to reconstruct a flight from previously recorded sessions allowing for realistic integration and debugging using actual flight data.

There are certainly applications in which a $30 adaptor is cost effective, if your application is one of these that’s what you should get. If not, we have excellent solutions for you.