USB Adaptor Isolates Multiple Serial Interfaces

You need a Swiss Army knife of serial communications? Ollie is a compact isolated USB adaptor that provides USB, CAN bus, and two UARTs at logic, RS-232, and RS-485 signaling levels, as well as an isolated power supply.  [Slimelec] has managed to squeeze all this into a package the size of a harmonica.  We like the technique of making the enclosure from PCB material, complete with clearly labeled switch, LED and connector pinout names.

So far, only the compiled firmware is available for this project, but hardware files, and presumably the source code and documentation, are coming soon.

The central themes here are  isolation and flexibility. We can’t find the isolation voltage in the project specifications, but the CANable project on which this adaptor is based provides 2.5 kV galvanic isolation.  A single isolated USB interface is also provided over a standard Type A connector. The four-wire logic-level UART signals are available on a 2 x 7 box header, and are voltage selectable.  The RS-232, RS-485, and CAN signals are on an 8-pin pluggable screw terminal block, or you can use a DB9 connector with a pluggable adaptor board.

Whether you need a troubleshooting aid for field testing, are using CAN bus on your projects, or just want to isolate your expensive computer from sketchy prototype hardware, have a look at this project.

33 thoughts on “USB Adaptor Isolates Multiple Serial Interfaces

  1. Just looking at the picture, it’s nice that the second layer of PCB is added to provide info on the pins. I bet that underneath he has removed all reference designators to cram more components in a smaller area.

  2. Just being critical but what exactly would one really need this for, it’s a beautiful end product but why is it an “adaptor” I guess I’d what I’m asking. What is it adapting and to what? I’m in need of more content to absorb about this thing. I’m guessing car hacking/tweaking?

    1. TBH I would love thing like this during my machines evaluation and start up, as usually I would carry at least three different RS485/RS422 converters, a CAN to USB converter and oscilloscope with me. Not to mention the driver mess on my PC to support different vendors converters.

      If working in field having small, multi standard converter would be awesome. The idea behind BusPirate was similar but was lacking isolation. And when first up bring of new machine is happening various stuff tend to go sideways, including 230V to USB :D

    2. This project combines multiple devices into one compact unit. It’s an adaptor because it connects your PC USB to:
      – UART
      – CAN
      – RS232
      – RS485
      – USB
      All the mentioned interfaces are isolated to help protect your PC.

      I will release more details on the use cases soon.

    3. Working in lots of environments you will connect to circuits that have different power supplies. Sometimes, communication wires are strung over long distances (like 1000 feet), and the ground potentials can be at different levels (example: ground A can be +20V offset from ground B). When you connect a non-isolated adaptor, you can basically short a voltage through your laptop. Bad things happen.

      It’s also really helpful to have RS485, RS232, and a bunch of other communication protocols in a tiny open source tool. I have had to carry around a bunch of dongles to connect to different equipment for troubleshooting communications in the past.

      I’d love to see a dongle-bridge, where you could use one isolated dongle on each end to create a bridge across another protocol (like RS485 serial via ethernet or optical to another RS485 serial connection). Like this: https://datainterfaces.com/frm220-serial-st002-rs-232-rs-485-rs-422-over-multimode-fiber-media-converter-2km-st-connector/

  3. Hopefully Slimelec will chime in here and explain HK’s motivation in more detail. Clearly, with the firmware’s emphasis on CAN, I gotta believe that automotive projects were foremost in his mind. But just the isolation feature alone, with or without CAN, can be very helpful in some situations. If you’ve ever fried a $2000 laptop doing surge current testing, or wanted to monitor serial links from a big industrial machine of unknown provenance, galvanically or optically isolated interfaces can be your friend.

    1. This is more like a Swiss Army knife as described in this article – The emphasis is more on isolation, CAN is the only interface that requires a firmware, the other interfaces are based on serial (except the isolated USB). So the motivation behind this project is to combine multiple devices that you would buy separately into one compact package and of course this will cheaper. If you do field work and travel around a lot this will save you a lot of space.

      Btw with the isolated USB port you can isolated any USB full speed device which comes in handy when debugging a main powered device.

      1. Indeed! Good point. Back in the 90s when I was working with CAN on a NASA rocket project that never got off the ground, it seemed folks used galvanic isolation to refer to transformer-coupled modules, in contrast to ones connected by fiber optics. I never sat back and realized they were the same. Well, kinda – all optical interfaces are galvanic, but not all galvanic ones are optical. Thanks for point this out.

  4. Would be great if there was some sort of LED indicating which lines are active. Finding a serial breakout board is difficult nowadays, but really useful when debugging some legacy stuff which makes interesting use of the CTS/RTS lines

    1. I agree that LED can be useful, but I wanted to keep things as compact as possible. And I also wanted to make it as affordable as possible that’s why I did not add any LEDs on the enclosure PCB to keep the assembly cost down.

    1. I’m planning to sell on tindie after the campaign. However early backers on Crowdsupply will get it at a discounted price. I’m also giving away 2 units for free, instruction on how to opt in can be found on the product page on Crowdsupply.

      1. As far as we know, the only thing digital in my 1986 AMC Eagle is the clock.
        Everything I’ve encountered to fix, has been analog so far.
        There is a ‘computer’ for emissions control, but it’s a black box to us.

  5. Looks really good. I can think of any use I would have for it though. At least not these days. Well maybe I’ll find myself itching for a +-12 volt capable serial gadget if I ever get back to working with some of my old Sun gear. I wonder what got him itching for something like this.

  6. I can’t wait until this becomes available… [from the site : this project is coming soon]

    Unfortunately there is so much stuff out there “coming soon” that never materialises. I really hope this one does.

    Also, on the ‘pinout’ diagram, I see ‘RSTA’ and ‘RSTB’. Should that not be ‘RTS’ (Ready To Send)?

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