gpib

10 Articles

An HP9863C partially disassembled on a workbench

Repairing A $25,000 HP Workstation To Run Pac-Man

June 20, 2023 by 21 Comments

The microcomputer revolution of the 1970s and 1980s turned computers from expensive machines aimed at professionals into consumer products found in the average household. But there always remained a market for professional users, who bought equipment that was so far ahead of consumer gear it seemed to belong in a different decade. While a home computer enthusiast in 1981 might fork out a few hundred dollars for an 8-bit machine with 64 KB of memory, a professional could already buy a 32-bit workstation with 2.8 megabytes of RAM for the price of a brand-new sports car. [Tech Tangents] got his hands on one of those machines, an HP Series 200 9863C from 1981, and managed to get it up and running.

The machine came in more-or-less working condition. The display cable turned out to be dodgy, but since it was just a straight-through sub-D cable it was easily replaced. Similarly, the two 5.25″ floppy drives were standard Tandon TM100-2As which [Tech Tangents] had some experience in repairing, although these specific units merely needed a thorough cleaning to remove forty years’ worth of dust. Continue reading “Repairing A $25,000 HP Workstation To Run Pac-Man“ →

This Rohde & Schwarz Computer Is A Commodore PET

June 14, 2023 by 24 Comments

The IEE-488 or GPIB bus for controlling instruments by computer has existed now for many decades. It’s often implemented over USB or Ethernet here in 2023, but the familiar connector can still be found on the backs of pricey instruments. In the earlier days of GPIB when a powerhouse Linux laptop was decades away, what computer did the would-be GPIB user reach for? If they were a Rohde and Schwarz customer in the late 1970s the chances are it would have been the R&S PUC process controller, an 8-bit microcomputer that under its smart exterior turns out to be an enhanced Commodore PET. [NatureAndTech] has one for teardown, and you can see it in the video below the break.

Readers with long memories will remember that the PET had an IE-488 bus on a card edge connector, and it’s possible that’s why R&S took it as the basis for their machine. But this isn’t merely a PET in a fancy box, instead it’s a fully new PET-compatible computer, and it has some interesting features. There’s more memory than the original, a set of disk drives, and an expansion bus complete with a high-res graphics card allowing pixel graphics rather than text. Surprisingly though it has a BASIC interpreter it’s a hardware clone of the PET only, the ROM is unique to Rohde & Schwarz.

We think this machine is probably rare enough that we’re unlikely to see one in the flesh, but it’s been a fascinating thing to examine. You can join in with the video below the break, or you can look at the PET’s impact on a more recent scene.

Continue reading “This Rohde & Schwarz Computer Is A Commodore PET” →

HP 3488A Teardown, Dismantled For Parts

March 17, 2023 by 10 Comments

[IMSAI Guy] has an old HP 3488A Switch Control Unit that he wants to dismantle for parts ( see video below the break ). The 3488A is pretty simple as far as HP test equipment goes — a chassis that can hold various types of relay cards and is programmable over GPIB. He notes up front that these are plentiful and inexpensive in the used test equipment market. Continue reading “HP 3488A Teardown, Dismantled For Parts” →

Open Source LXI Tools Free Us From Vendor Bloat

February 18, 2022 by 8 Comments

LXI, or LAN eXtensions for Instrumentation is a modern control standard for connecting electronics instrumentation which supports ethernet. It replaces the older GPIB standard, giving much better performance and lower cost of implementation. This is a good thing.  [Martin Lund] has created the open source lxi-tools project which enables us to detach ourselves from the often bloated vendor tools usually required for talking LXI to your bench equipment. This is a partial rewrite of an earlier version of the tool, and now sports some rather nice features such as mDNS for instrument discovery, support for screen grabbing, and a LUA-based scripting backend. (API Link)

SCPI or Standard Commands for Programmable Instruments is the text-based language spoken by many instruments, allowing control and querying of an instrument. Just to be clear, SCPI is not at all a new thing, and older instruments that have GPIB or RS232 connectors, still could talk SCPI. lxi-tools is not for those. Some instruments can also be very picky about the formatting of commands, especially if they’re buggy, so the ability to interactively debug commands is very desirable. It is quite possible to make poor use of SCPI commands in your test script and end up with tests that just take far longer to execute that they need to. lxi-tools has a benchmarking tool too, which helps you to dig in and find out where all the time is going and make suitable adjustments.

We’ve not seen much about LXI on Hackaday, but we did cover using PyVISA for dealing with SCPI-over-GPIB in python.  If you have an older instrument  with GPIB and you don’t want to sell a internal organ to pay for a USB adaptor, here’s one you can make yourself.

Save Money And Have Fun Using IEEE-488

January 31, 2022 by 32 Comments

A few months ago, I was discussing the control of GPIB equipment with a colleague. Based on only on my gut feeling and the briefest of research, I told him that the pricey and proprietary GPIB controller solutions could easily be replaced by open-source tools and Linux. In the many weeks that followed, I almost abandoned my stance several times out of frustration. With some perseverance, breaking the problems into bite-sized chunks, and lots of online searching to learn from other people’s experiences, my plan eventually succeeded. I haven’t abandoned my original stance entirely, I’ve taken a few steps back and added some qualifiers.

What is GPIB?

Example of HP-IB block diagram from the 1970s, from hp9845.net

Back in the 1960s, if test equipment was interconnected at all, there weren’t any agreed-upon methods for doing so. By the late 60s, the situation was made somewhat better by card-cage controller systems. These held a number of interface cards, one per instrument, presenting a common interface on the backplane. Although this approach was workable, the HP engineers realized they could significantly improve the concept to include these “bridging circuit boards” within the instruments and replacing the card cage backplane with passive cables. Thus began the development of what became the Hewlett-Packard Interface Bus (HP-IB). The October 1972 issue of the HP Journal introduced HP-IB with two main articles: A Practical Interface System for Electronic Instruments and A Common Digital Interface for Programmable Instruments: The Evolution of a System. Continue reading “Save Money And Have Fun Using IEEE-488” →

Keep Both Hands On The Probes With This Oscilloscope Footswitch

December 2, 2018 by 18 Comments

We’ve got two hands, so it’s natural to want to use both of them while diagnosing a circuit with an oscilloscope. Trouble is, keeping both hands on the probes makes it a touch difficult to manipulate the scope. If only there were some way to put your idle lower appendages to work.

This multipurpose oscilloscope footswitch interface makes so much sense that we wonder why such a thing isn’t standard equipment on more scopes. [Paul Roukema]’s interface relies on the USB Test and Measurement Class (USBTMC) protocol that allows most modern scopes to be remotely controlled, somewhat like the General Purpose Interface Bus (GPIB) protocol of old. [Paul]’s interface uses an STM32 microcontroller to talk USBTMC to either Keysight’s Infinium scopes or the Tektronix DPO line, since those were what he had to test against. Tapping the footswitch cycles the acquisition mode on and off or triggers a single acquisition. He’s thoughtfully included the USBTMC specs in his GitHub project, so adapting it to other scopes should be straightforward. We’d even wager that older scopes with GPIB could enjoy the same handsfree control.

Have a down-market scope but still want to go handsfree? [Jenny List]’s primer on running a Rigol with Python might offer some hints on where to start.

Data Logging Like It’s 1982

July 26, 2018 by 26 Comments

If you want to log voltages or resistance these days, no problem. You can buy a multimeter with Bluetooth for a hundred bucks, and if you’re really fancy you can spring for the Fluke with a graphical display that will log values automatically. Things weren’t always this cheap and easy, but there was always a way to do it.

Back in the 80s, HP had GPIB, or HP-IB, or IEEE-488 connectors on the back of their benchtop equipment. This was an 8-bit interface not unlike a parallel port that allowed for remote control of test equipment. In a great demonstration of what this was actually like, [AkBKukU] posted a video of connecting an old benchtop multimeter to a vintage computer over GPIB.

The computer used for this feat of retrotechtacularness is an HP Series 80, a footnote in the history of desktop computers, but it does have a custom CPU and BASIC in ROM. As you would expect from vintage HP gear, there are a few slots on the back of the computer for connecting interface boxes, including a modem, a speech synthesizer, and of course, an HP-IB interface that can speak IEEE-488.

With the multimeter connected to the computer over the daisy-chainable parallel interface, it was a simple matter of writing a little bit of BASIC to read a potentiometer and a thermistor. With a little bit more code, this computer can even produce a graph of the resistance over time. This is data logging like it’s 1982, and it’s a fantastic example of exactly how far we’ve come.

Continue reading “Data Logging Like It’s 1982” →