Monday, October 8, 2007

Legacy test systems

Over the past few months I’ve written a few times about different types of test engineering. Last Friday I faced a seamier side of test engineering: legacy systems.

I don’t want to discuss the work in detail and bore everyone, so here is a synopsis:

- I’m overseeing a test system that has to be ready in a month.

- The system has hardware that was designed decades ago, and some of the software was written a good dozen years past, based on software even older.

- I scheduled a consultant to fly in from California on Monday to work on a newer part of the system.

- I’ve had an engineer and an intern do some preliminary setup work.

On Thursday afternoon I was performing last minute checks and couldn’t get the auto alignment system to work – the camera would not capture any images. Friday morning I dug into it further & found that the entire motion control system (the 20+ year part of the system) was motionless. I talked with an engineer at the firm responsible for the system, and he was wracking his brain trying to remember some of the details. Great.

The whole motion system is controlled through a single a serial port. After having little luck with the phone support, I tried wiring pin 2 to 3 (output to input) to test the port itself. It was fine. I tried swapping out card cage boards with systems that were working. No luck. I even swapped out the image grabber card, but that didn’t work either. After an entire day of work, I finally found the problem: a combination of a flaky PCI slot and an incorrect software setting.

The point of all this is that sometimes the systems you use for testing are not your own. They’re old. Yes, they work, but they can be finicky. The documentation is incomplete, you don't have access to the source code, replacement parts are hard to find. Sometimes that’s just part of the job.

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