Test labs asked to affirm USB, 1394 compliance

Test labs asked to affirm USB, 1394 compliance
By Junko Yoshida, EE Times
November 14, 2001 (6:42 p.m. EST)
URL: http://www.eetimes.com/story/OEG20011114S0064

SAN MATEO, Calif. — Makers of USB or IEEE 1394 devices are increasingly asking independent testing laboratories to help ease the laborious task of compliance testing.

The turn to the labs comes as industry groups seek more-effective tools to design comprehensive test suites for the so-called "plugfests." These efforts include the 1394 Trade Association's recent adoption of the Tree and Tabular Combined Notation (TTCN) standard.

When lesser-quality 1394 or USB devices show up on the market, component and system vendors must maintain a high-quality standard for their interfaces to keep their systems compliant to the standard. "We need to stave off cheaper imitations," said Max Bassler, chairman of the 1394 Trade Association.

Moreover, putting in place effective testing methods is especially critical, since trade groups like the 1394 body and the USB Implementers Forum (USB-IF) are under pressure to succeed with new logo and icon programs intended to insure interoperability among various systems — both on the electrical and system-application levels.

The USB-IF has been certifying several third-party labs to test USB devices — not only for USB cables and connectors but also for USB devices, hubs, systems and silicon building blocks. The USB-IF recently added MCCI (Ithaca, N.Y.), a developer of USB drivers and firmware, as a newly certified USB 2.0 low-, full- and high-speed device-testing lab. Others already certified by the USB-IF include NSTL Inc. (Conshohocken, Pa.), Professional Multimedia Testing Centre (Belgium), XXCAL (Culver City, Calif.), Contech Research Inc. (Attleboro, Mass.) and ETC (Taiwan).

Meanwhile, the 1394 Trade Association recently decided to use the TTCN standard for 1394 protocol conformance testing. TTCN, an ISO/IEC 9646 standard originally designed for telecom, where robust protocol conformance is mandatory, is "a formalized language to describe test suites," said Richard Mourn, president of Quantum Parametrics (Scotts Valley, Calif.).

The 1394 Trade Association expects to apply TTCN-based tests in all IEEE 1394 specs that include command sets or protocols above the physical (PHY) layer, including updates and enhancements.

Since TTCN turns test specs into C function calls for real-world applications, it can spare the human labor of reading, interpreting and then translating into hard code a system specification originally written in English, Mourn said. In essence, TTCN can develop a test suite that looks and feels identical in each application, regardless of its author.

Plugfest limits

MCCI president Terry Moore said plugfests represent a growing problem today as more USB devices hit the market. "It has become difficult to manage testing so many devices in such a short period of time — like three days — during one plugfest," he said. Moreover, waiting the customary three months for another plugfest to test one's product has become unacceptable for those seeking fast er time-to-market solutions. "For many companies, three months is a lifetime," Moore said.

Some vendors also worry about confidentiality. While it's customary for compliance testers and those who bring proprietary, unannounced devices to plugfests to sign nondisclosure agreements, the testing, by nature, is a semi-public forum. Although system vendors try to conceal a new product in a paper bag or a cardboard box, "you'd know what they have, as you wait in line" for their verification tests to finish, said Moore.

Instead of going through an often-torturous plugfest, system vendors can now go to private testing labs certified by the USB-IF. The goal for MCCI, for example, is to test a USB system product in about two weeks without requiring product engineering staffers to attend, said Moore.

The 1394 Trade Association plans to follow the path innovated by the USB-IF, said Bassler. The association is now "interviewing one or two labs" that can test 1394 cables and connectors for compliance testing, he said.

The search for third-party testing labs that can test physical-level conformance as well as the Open Host Control Interface (OHCI) has also begun, Bassler said. Quantum Parametrics has already submitted a proposal to the 1394 body, he said. "Eventually, we'd like to see about 10 different companies getting involved in setting up this process."

Technical confidence

The flurry of test activity among trade groups stems from the industry's pressing need to reduce the burden — now unfairly placed on consumers — of sorting out complex digital connectivity and interoperability issues. As they roll out new logos and icons, system vendors want to ensure both electrical and functional conformance. Previously, private logos such as i-Link and Firewire that appeared on systems were just a marketing device, said Mourn. "With our new 1394 logo program, however, we want to build technical confidence behind that logo."

Next year, the 1394 Trade Association will roll out a new compliance logo for its members and a new compliance icon for consumers to identify the right sockets and the right connectors to buy, Bassler said.

The 1394 body is heading for uncharted waters that USB-IF has never had to sail, especially in ensuring function-level conformance for various 1394 equipped systems. Because of USB's fundamental master/slave model, conformance testing for USB devices is relatively painless, as long as companies like Microsoft Corp. or Intel Corp. have correctly implemented the USB host on the PC platform.

In contrast, the peer-to-peer communications for which 1394 is designed could create a whole new set of problems. Besides checking the electrical properties in baseline 1394 test suites, the 1394 group also needs to implement "network testing" as well as "functional conformance test suites," Mourn said.

Network testing is critical, to assure that a new 1394 device added to the 1394 network can not only perform its functions properly but also does not disrupt other devices already on the network. TTCN comes in handy "because we can use the language to emulate the traffic on the network," said Mourn. "We can track the traffic and try to determine what's happening in the real-world scenario."

Functional conformance test suites will grow over time, said Mourn. Today, a digital-video camcorder and a hard-disk drive — even though each is equipped with a 1394 interface — have no idea what they are supposed to do on an application level when the two are connected. To make that connectivity useful for applications, the 1394 trade group first needs to determine "profiles" — a set of certain minimum functions all digital-video camcorders or all the hard drives can perform. Again, the TTCN will play a critical role in developing standard test specs that fit across different devices ranging from high-definition TVs, notebooks and set-tops to personal video recorders and cameras.

The testing complexity that faces the 1394 association today will likely have g reat relevance to the USB group when it begins to deal with the emerging USB-On-The-Go spec. Unlike regular USB, USB-On-The-Go is set up for point-to-point communications — without a PC to bridge two devices — in a fashion similar to 1394. With USB-On-The-Go, Mourn said, the USB group "will have to solve problems we are already solving with 1394."

TTCN has not been discussed in the USB community yet, MCCI's Moore said. But he acknowledged that TTCN might be useful for creating USB-On-The-Go testing procedures. Moore said that unlike 1394, USB-On-The-Go allows a collaborating pair of devices to elect a host device. After the election, the existing USB host/device protocols are still used. Nevertheless, USB-On-The-Go opens new challenges in testing. System vendors need to design test cases that will challenge a device under test with electrical scenarios that cover many real-life situations the device might see, Moore said.