On The Move


Importance of Hardware Testing – Interview with Chris Loberg (Part 1)

I just returned from the MIPI Alliance Face to face meeting in Vancouver where I participated in several discussions with MIPI alliance members about the importance of testing.

This is a timely topic as Tektronix announced their Tx and Rx test coverage for MIPI M-PHY v1.0 spec. And I wanted to learn a bit more about this subject and share with you so I used the opportunity to discuss the importance of hardware testing with Chris J. Loberg, Sr. Field Technical Marketing Manager for performance oscilloscopes at Tektronix. Here are the Questions and Answers used in this interview, feel free to comment and ask your own questions, we’ll do our best to respond.

Question: Recently Tektronix announced Comprehensive Transmitter and Receiver Test Coverage of New M-PHY v1.0 Specification which offers mobile device hardware engineers a simple, integrated solution for M-PHY Transmitter and Receiver debug, validation and conformance testing needs. Can you explain what this is ?

Answer: The diagram shows a setup supporting the testing platform, this is a system that work in tandem.

The goal of the product is detect any errors on the DUT (M-PHY device). First step, you need to calibrate the generator that will create amount of errors and check they are recognized on the oscilloscope side.
The calibration method transmits an (8b10b encoded) pattern and stressors for the M-PHY signals (such as jitter and noise). The scope error detect will look at transitions outside the window and count for errors.
After that, you connect the setup to the DUT (M-PHY device) and use the oscilloscope to detect and record the errors.

Hezi’s comment: Here’s a link to the M-PHY characterization video Synopsys produced that shows some tests that we’ve done: www.synopsys.com/mphy

Question: I see that your setup supports both M-PHY and D-PHY versions, how important do you see support of multiple PHY/protocol test environment ?

Answer: The speed of the signal and pattern type will vary between the two PHYs as there is a different traffic and payload therefore the scope will look at different things.
The advantages to the test engineer that uses different standards are in helping the usability and instrument investment turn around when standard changes.
These are fairly new standards and the engineer doesn’t need to be cognoscente of new standards and versions as they come up.
Furthermore, the test setup for these protocols when generation changes (D-PHY to M-PHY and to different gears) becomes more complex. The engineer needs to go setup timing relationship and have expertise in all variations of spec.
Having a common test instrumentation helps meet cost savings in the lab that handle both generations. From individual test engineer perspective there is an increased productivity as the engineer could rely on the instrument test manufacturer to help make the transition to the new spec.

Question: As the MIPI M-PHY is targeted to be used for many and different protocols, can you share with us what Tektronix have done to develop this kind of setup ?

Answer: Tektronix worked closely with MIPI alliance to review compliance testing for D-PHY and M-PHY. This allows figuring out the performance and electrical testing requirements which are designed into the setup tied to each revision of the MIPI standards.
One of the things that are unique for MIPI alliance specifications is that is more flexible than other standards. PCIe and USB test spec requires well defined area of pass/fail compliance and not a lot of interpretation to conform outside the spec. There is more room for interpretation for the MIPI alliance spec’s and there is no formal logo compliance program. Tektronix supports this kind of flexibility with a tool DPOJet that allows customer to change clock frequency upwards without modifying the amplitude.

More from this interview next time, stay tuned…

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