Tektronix DPO USB Interface

1973’s Tektronix Digital Processing Oscilloscope (or “DPO” for short) was comprised of a 7704A ‘scope and a P7001 digitizer, processor, and memory unit. The processing unit could in turn be connected to an external computer, such as the PDP–11 16-bit minicomputer from Digital Equipment Corporation.

This would have been a dream setup in the 1970s, but in the modern era, the chances of finding a working PDP-11 hanging around to plug your old ‘scope into are rather rare. Which is why Holger Lübben designed the Teensy 4.1-based USB+ Interface, to replace the slow GPIB interface (which was limited to about 50 data words per second) and allow direct connection to a modern PC over USB.

The USB+ Interface is connected directly to the internal bus of the P7001 unit, allowing interaction with every aspect of the instrument, including other plug-in cards. Level shifters facilitate interaction with the 5V system. The software-controlled X/Y mode of the P7001 allows arbitrary vectors to be drawn on the ‘scope, which Holger used to create an on-screen menu to help navigate custom software, such as demos, calibration tools, and even a joke of the day. Extensive detail about the project including pictures, documentation and further resources can be found on the project’s web page.