HP16500B Logic Analyzer Controlled With RS-232 And More


We’re pretty spoiled these days in that hobby electronics has made a lot of cool tools available on a budget. It’s hard to think of a better example than a logic analyzer, which you can get for a day or two of pay. Consumer-level devices just didn’t exist until a few years ago. [Jouko S] has this HP16500B industrial grade logic analyzer in his shop. It’s from the early 1990’s and it’s got a ton of features. Grabbing a still functional yet super-old model used to be the only way for hobbyists. But one thing you won’t find on it is the ability to connect it to your USB port to get screen captures. Younger readers might not recognize the slot at the top for magnetic media called a floppy disk which is the in-built way of recording your sessions. He set out to find an easier way to get color screen captures and ended up adding RS-232 control to the old hardware.

There is a 25-pin port on the back of the old hulk. But it is a female connector and he didn’t have the adapters on hand to make it work with his serial-to-USB converter. During development he used a breadboard and solder-tail connector to patch into the necessary signals. This was all hooked up to a Raspberry Pi which he planned to dedicate to the system. It worked, and he was able to use an interactive terminal for the rest of his sleuthing. With much trial and error he figured out the commands, and wrote some Python code for the Pi side of the equation. He can now pull color screenshots with ease thanks to the utilities available in the Python Imaging Module.

15 thoughts on “HP16500B Logic Analyzer Controlled With RS-232 And More

  1. You can purchase an inexpensive USB Drive adapter that plugs into and emulates the 1.44″ FDD. Equipment operation is not changed. Granted, you have only 1.44 MB storage on whatever USB Thumb Drive you use … much better than taking screen photos with your phone. There are also USB Drive adapters that provide the means of selecting multiple files … emulating a box (case?) of 1.44″ floppies for not much more … though you do have to bring that switching outside the box.

    1. Not so “easy”. The pinout of the floppy on the 16500B is waayyy different of a standard drive. And also, he could pull these images from the network card. And if he doesn’t have the network card, can buy one for way less the price of a Raspi. Maybe the owner should be directed to the yahoo’s hp_agilent_equipment list…

      1. Last I checked the network modules would have cost nearly as much as I paid for the entire system and at least three times the price of a Raspi plus postage. The point of this was to provide remote access to the instrument without requiring to obtain such a module.

    1. Under 500 of your american dollars would be my guess – ebay had loads last time I looked. They’re nice bits of kit, the HP analysers (used to have one professionally), but they boot off floppy IIRC which would make me a bit nervous, and max capture rates are a bit limited by today’s standards.

      1. Watch eBay for a while and you can find a 16500B or 16500C for about $300. Educate yourself on the various plugins first, for their capabilities vary widely. They boot from an internal HD. I don’t know if booting from a floppy is possible, but it is certainly not the norm. A reasonably fast scope module is available, about 400 Msample/sec. As for limited capture rates, mine is capable of 500 Msample/sec logic analysis. That compares quite favorably with most of the inexpensive USB-based $50 units. Another advantage is the modular construction: swap out a defective module in 5 minutes, or if your mainframe dies, buy a new unit and move your modules into it. That said, being able to drop one of the USB devices in your pocket instead of lugging the 50lb HP around is quite attractive. Also unavailable on the HP is the protocol decoding (SPI, I2C, async, etc) sported by the new portable devices.

        1. I used to be a 16500 jockey back in the day. The triggering setup on this beast is amazing. I would regularly forgo using the newer, faster Windows based Teks in favor of one of these. Bonus if you have a 16500C: you can get at the UI remotely with XDMCP.

  2. The 16500A was a weakly upgradable model, with a general recommendation to be avoided for the 16500C
    The 16500B has a different mainboard than the A, including memory that can be upgraded through 72 pin SIMMs. I’ve personally got a pair of parity 32s in mine, how much the software takes advantage of it is another question.
    There is an expansion card for the B model, the 16500H, which adds a 10megabit ethernet port, and a high-speed SCSI port to interface to a 16505A prototype analyzer, addressable as a SCSI device using a similar means as the RS232 interface protocol. Given that the networking capability is slow and sometimes flakey, SCSI might be a nicer interface.
    GPIB is a given, of course. The A and B models used HIL interface keyboards and mice, but HP wised up on the C and switched to PS/2.
    If you’re fortunate enough to have networking on the B, or C, you can control the screen remotely over an X server, which is quite nice for use of a keyboard, and avoiding filthying up your touchscreen.
    All machines can boot off of a floppy, if there’s one in the drive during powerup and if it has the appropriate files on it. Otherwise it loads off of a plain ATA hard disk – which can be changed out for a choice CF card in an adapter. I’m told the operating system is based on HP-UX or something to that effect.
    This is only really skimming the surface, the module choices (state/timing analyzers, DSO cards, pattern generators…) and software interractions between them fill a nice stack of three-ring tomes worth of reading. There’s so much I’m sure I’ve forgotten a point, and know I’m skimping on many details. Just got my own, thought I’d try and share.

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