It doesn’t take much examination of modern automobiles to figure out that they have become vastly more complex in just a few years. Even if you consider only the boom in infotainment systems, the amount of electronic content that vehicles use has exploded.
But it’s not all glitz and glamour when it comes to electronics and the automobile. Almost everything in today’s vehicles is under the sway of an electronic control unit (ECU), and that includes the safety features that we depend on to save lives in the event of a collision, most notably the braking systems.
Thus, the ante for testing the electronics in our vehicles is raised considerably. Compounded by the exploding complexity, functional test is a critical aspect of the design and development cycle in Detroit, Tokyo, and everywhere else vehicles are conceived.
Summing Up The Challenges
A key issue for automotive test is the proliferation of extremely complex distributed networks within today’s vehicles. There may be hundreds of ECUs that must communicate with each other over serial buses with fairly complex protocols. These include the CAN, LIN, and FlexRay buses. Moreover, a given distributed network may mean multiple buses with different protocols, or the same protocol with multiple signal speeds. That will introduce the need for gateways to help transition signals between these various bus protocols and/or signal speeds.
Most of today’s bench oscilloscopes from all of the major manufacturers (Agilent, LeCroy, and Tektronix) offer built-in serial analysis capabilities that enable you to trigger on specific data, address protocols, or errors on the bus. These scopes will also decode and search for specific packet content.
A related issue concerns the troubleshooting of the overall system, which means dealing with the gateways between multiple buses and protocols. This requires timing analysis to determine the causes of lag on packets as they migrate from bus to bus. In turn, this means being able to look at these multiple buses passing through the gateway simultaneously. Thus, the oscilloscope needs to support multiple speeds and decoding on multiple buses. Here again, all of the major scope makers provide equipment that fulfills these requirements.
“Our 5000 series scopes can view up to 16 decoded buses,” says Gina Bonini, technical marketing manager at Tektronix. “I’ve never seen a customer who needs to do that, but we do see the need to look at up to five buses to examine their relationships through the gateway.”
Scopes with built-in serial decoding aren’t new, of course, but Bonini expressed surprise that many engineers still aren’t aware that this functionality is available.
“Especially in the automotive space, this tool on a scope is a huge time saver,” says Bonini. “You can set up a hardware-based trigger in which the scope is looking at the incoming signal and watching for a packet. It can home in on very specific data. The scope monitors the incoming signal until it sees that data and then triggers.”
In capturing signals for this process, modern scopes can take in many millions of data points, which translates into many thousands of packets. The scopes’ search tools can then be applied to find specific addresses, data packages, or errors. “This not only helps to validate the bus but also helps you to see what is really happening in your system,” says Bonini.
Another trend complicating automotive test is the proliferation of wireless. Wireless sensors for tire-pressure monitoring, Bluetooth connectivity from cellular handsets to the vehicle, and other wireless sensors mean that test engineers must deal with RF signals. An instrument such as Tektronix’s recently introduced MDO4000, which combines an oscilloscope with a spectrum analyzer, is well suited for debugging and troubleshooting such wireless links (see “A Hands-On Look At Tek’s MDO4000 Mixed-Domain Scope” at www.electronicdesign.com).