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SMALL FORM FACTOR FORUM

January 2011

The Little Engine that CAN

COLIN MCCRACKEN & PAUL ROSENFELD

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In a surprising new round of I/O Whac-a-mole, embedded SBCs are popping up all over the place with an onboard interface that used to require a separate I/O expansion card. Once relegated to automotive applications, the Controller Area Network (CAN) bus can now be found in myriad industrial automation, military and even some medical applications. So CAN interfaces on SBCs shouldn’t be a surprise; applications seem to be the driving force. That should make for an interesting Embedded World in Germany this year. The Germans savor their CANbus just like a tall cold weissbier in the Altstadt.

Actually, this latest SBC trend hasn’t come about due to target application demand. The new Intel Atom E-series (“Tunnel Creek”) processor family is behind it. Or, to be more precise, its companion chip, the E620T “Topcliff” I/O Hub, is the culprit. Despite repeated denials from the chip manufacturer that it is not targeting only high-volume “IVI” (In-Vehicle Infotainment) applications (“car PCs” in lay terms), all signs point to IVI as the target market for this processor / I/O Hub combo. The result is an integrated CANbus controller in the E620T chipset.

Once again, the broad embedded market reaps rewards from the 15-billion-connected-devices strategy of the mother ship. For that, we are eternally grateful, as we understand that rising development costs will forever prohibit a true “designed by embedded, for embedded” x86 system on chip. But even a leftover meal still counts as a meal. Not only will automotive, military vehicle and factory applications enjoy reduced size, weight, power and cost (SWaPaC) compared to legacy PC/104 card stacks, but this free integrated CAN controller has the potential to drive the adoption of CANbus and its high-level protocols into completely new applications.

The significance of this milestone cannot be understated. SBCs ranging from motherboard form factors down to PC/104 SBCs will become available in 2011 with a CAN-do attitude. This will gradually reduce the need for legacy single-purpose and even multifunction I/O cards. Four free serial ports in that same I/O hub just add more fuel to the fire. Yes, after years of stripping application-oriented I/O and buses out of the chipset for desktop and laptop use, a reversal of fortune has come from a most unsuspecting place. And as usual, for all the wrong reasons—but who’s complaining?!? Say “Thank you” and don’t bite the hand that feeds us.

SBCs have the intrinsic luxury of supporting new I/O features, such as CAN, via pin headers or PC-style connectors while maintaining existing standards (board form factors and bus connectors). It’s a good thing, since it takes far too long for trade groups to wrangle through even simple changes to standards, and legacy compatibility is usually sacrificed. Unfortunately, life is not so easy for the fragmented computer-on-module (COM) form factor standards since, by definition, the only path off the board for chipset signals is through the baseboard connector(s). With hundreds of signals crammed onto high-speed-capable surface mount connector pins, standards architects rarely leave any reserved pins for future “unanticipated” chipset interfaces. Consequently, most COMs are CAN’t-do when it comes to the E620T windfall. Major changes will be required to take advantage of the new “free” CAN interface.

COMs have rapidly penetrated most high-volume market segments. These small form factor modules contain only the processor, memory, chipset and LAN controller, which form the greatest common factor (subset) of modern embedded apps. COMs are the little engines that run the system software—OS(s) and application(s)—that power each baseboard full of I/O boxcars, hopper cars and tanker cars that are hooked together to form each unique embedded system. Of course, not encumbering COMs with the particulars of diverse applications was what allowed COMs to reach heads of steam in the first place. But the lack of an easily implemented CANbus might keep the latest round of little engines from crossing over into CAN territory the way that new SBCs can.

Quietly, a dark horse express train is chugging along new high-speed digital-only COM tracks. CoreExpress is the first open standard COM form factor to feature CAN support. While rival standards sit stranded at their respective bridges, scrambling to lay tracks for new pinout types, the CoreExpress form factor enters the scene as the Little Engine that CAN. Could this be a sign that other “application COMs” are just around the corner? We will all have to put our ears to the ground to find out.