Vintage Test Equipment Addiction Justified

Recore 3D printer board developer [Elias Bakken] has posted about the automatic test procedure he developed using a stack-up of four (at least) pieces of vintage HP test equipment. In addition, his test jig and test philosophy is quite interesting.

Besides making a bed-of-nails test jig, he also designed a relay multiplexing board to that selects one of the 23 different voltages for measurement. We like his selection of mechanically latching relays in this application — not only does it save power, but it doesn’t subject the test board to any magnetic fields (except when switching state).

In [Elias]’s setup, the unit under test (UUT) actually orchestrates the testing process itself. This isn’t as crazy as it might sound. The processor is highly integrated in one package plus external DRAM. If the CPUs boot up at all, and pass simple self-test routines, there’s no reason not to utilize the on-board processor as the main test control computer. This might be a questionable decision if your processor was really small with constrained resources and connectivity. But in the case of Recore, the processor is a four-core ARM A53 SoC running Debian Linux — an arrangement that itself could well serve as an automated test computer in other projects.

In the video down below, [Elias] walks us through the basic tests, and then focuses on the heart of the Recore board tests: calibrating the input signal conditioning circuits. Instead of using very expensive precision resistors, [Elias] selected more economical 1% resistors to use in the preamp circuitry. The tradeoff here is the need to calibrate each channel, perhaps at multiple temperature points. This is a situation where using a test jig, automated test scripts, and and stack of programmable test equipment really shines.

[Elias] is still pondering some issues he found trying to calibrate thermocouples, so his adventure is not quite over yet. If you are wondering what Recore is, check out this article from back in June. Have you ever used the microprocessor on a circuit board to test itself, either standalone or in conjunction with an external jig? Let us know in the comments below.

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Samsung’s Leap Month Bug Teaches Not To Skimp On Testing

Date and time handling is hard, that’s an ugly truth about software development we’ll all learn the hard way one day. Sure, it might seem like some trivial everyday thing that you can easily implement yourself without relying on a third-party library. I mean, it’s basically just adding seconds on top of one another, roll them over to minutes, and from there keep rolling to hours, days, months, up until you hit the years. Throw in the occasional extra day every fourth February, and you’re good to go, right?

Well, obviously not. Assuming you thought about leap years in the first place — which sadly isn’t a given — there are a few exceptions that for instance cause the years 1900 and 2100 to be regular years, while the year 2000 was still a leap year. And then there’s leap seconds, which occur irregularly. But there are still more gotchas lying in wait. Case in point: back in May, a faulty lunar leap month handling in the Chinese calendar turned Samsung phones all over China into bricks. And while you may not plan to ever add support for non-Gregorian calendars to your own project, it’s just one more example of unanticipated peculiarities gone wild. Except, Samsung did everything right here.

So what happened?

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Process Characterization On The Cheap With A Custom Test Rig

Testing is a key part of any product development cycle. Done right, it turns up unknown bugs and problems, and allows for them to be fixed prior to shipment. However, it can be a costly and time-consuming process. The [Bay Libre] team needed to do some work on power management, but the hardware required was just a little on the expensive side. What else does a hacker do, but build their own?

Enter the Thermo-Regulated Power Measurement Platform. It’s a device designed to control the die temperature of a chip during process characterization. This is where a chip, in this case the iMX8MQ, is run at a variety of temperatures, voltages, and frequencies to determine its performance under various conditions. This data guides the parameters used to run the chip in actual use, to best manage its power consumption and thermal performance.

The rig consists of a Peltier element with controller, a heatsink, and a fan. This is lashed up to a series of Python scripts that both control the chip temperature and run through the various testing regimes. Thanks to this automation, what would normally be a day’s work for an engineer can now be completed in just two hours.

Through a few smart component choices, the team accomplished the job at around one-tenth of the cost of commercial grade hardware. Granted, the average hacker probably won’t find themselves doing process characterization for cutting-edge silicon on a regular basis. Still, this project shows the value in building custom hardware to ease the testing process.

Testing is key to success in production. Custom jigs can make for light work when large orders come in, and we’ve run a primer on various testing techniques, too.

Custom Jig Makes Short Work Of Product Testing

When you build one-off projects for yourself, if it doesn’t work right the first time, it’s a nuisance. You go back to the bench, rework it, and move on with life. The equation changes considerably when you’re building things to sell to someone. Once you take money for your thing, you have to support it, and anything that goes out the door busted is money out of your pocket.

[Brian Lough] ran into this fact of life recently when the widget he sells on Tindie became popular enough that he landed an order for 100 units. Not willing to cut corners on testing but also not interested in spending days on the task, he built this automated test jig to handle the job for him. The widget in question is the “Power BLough-R”, a USB pass-through device that strips the 5-volt from the line while letting the data come through; it’s useful for preventing 3D-printers from being backfed when connected to Octoprint. The tester is very much a tactical build, with a Nano in a breakout board wired to a couple of USB connectors. When the widget is connected to the tester, a complete series of checks make sure that there are no wiring errors, and the results are logged to the serial console. [Brian] now has complete confidence that each unit works before going out the door, and what’s more, the tester shaved almost a minute off each manual test. Check in out in action in the video below.

We’ve featured quite a few of [Brian]’s projects before. You may remember his Tetris-themed YouTube subscriber counter, or his seven-segment shoelace display.

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