Reverse Engineering Teaches an Old Scope New Tricks

[PMercier] clearly loves his old Tektronix TDS3014 scope, which did however lack essentially modern connectivity such as an Ethernet port for control and a USB port for a convenient way to capture screenshots. So he decided to do some in-depth reverse engineering and design his own expansion card for it. The scope already has an expansion port and an expansion card, but given this model was first released in 1998, purchasing an OEM part was not going to be an option.

They don’t make ’em like they used to. Test equipment is today is built to last a decade — but usually lives on much longer. This is certainly true for the previous generations of kit. It’s no surprise that for most of us, hand-me-downs from universities, shrewd eBay purchasing, and even fruitful dumpster dives are a very viable way to attain useful and relevant test equipment. Now, while these acquisitions are more than adequate for the needs of a hobbyist lab, they are admittedly outdated and more to the point, inaccessible from a connectivity and communication standpoint. A modern lab has a very high degree of automated data acquisition and control over ethernet. Capturing screen dumps on a USB is a standard feature. These modern luxuries don’t exist on aging equipment conceived in the age of floppy disks and GPIB.

The first step [PMercier] documents is reverse-engineering the pin-out of the custom expansion connector on the scope. Some pins he notes were easy to deduce, others not so much. This was solved by examining some high-resolution photos of the original expansion card and then using Gimp to do a layered, copper track analysis of the 4 layer PCB! This uncovered most of the unknown pins and the rest required a laborious cross-examination of the scope’s CPU and its BGA package pin-out.

The last piece of the puzzle was to fool the scope into accepting his DIY expansion card. This turned out not to be as simple as pulling a control line. The correct one-hot encoded byte corresponding to the expansion card had to be determined and asserted onto the data bus at the right time.

This is truly a commendable Hack and we thank [PMercier] for meticulously documenting his progress! If rejuvenating old test equipment excites you, check out our article on reverse engineering an old HP scope to give it a new LCD screen.