A couple of days ago I needed a RS232 to USB adaptor.
Went to a store:
Me: Do yo have any RS232 to USB adaptor?
Him: Only to USB-C
Me: Ok... Now I just need a USB -> USB-C adaptor
Him: But what kind of TV do you want to connect?
Me: Wait. WHAT?
Him: Yea, you want a VGA to USB? Why do you need that?
Me: No, RS232, I don't need VGA...
Him: Ah... ok, no... we don't have any...

(Funny story... almost the same happened in 3 stores in a row....)

  • 13
    People working in electronics stores are 20 somethings that don't know shit. I needed a VGA to HDMI adapter. Guy at Worst Buy tried to tell me that HDMI to VGA would work in reverse. I was like dude, no it won't. The package even said it would not.
  • 7
    If you are trying to find something like this, the store is the last thing that should come to your mind
  • 1
    On Amazon the first hits on first page for "usb rs232" are all Type A to RS232.
  • 6
    Here's a nugget that's nice to know: I've seen some RS232 devices (mostly industrial ones) that don't work with USB-to-RS232 adaptors. That's because they have series resistors in the data lines for EMI protection.

    Unfortunately, these resistors also divide the voltage down. No issue with regular RS232 where the voltage level is 12V, but the USB things only give 5V level, and then it's not enough.

    You can spend muuuuch time figuring out what's wrong if you don't know this. Oh yeah. :/
  • 1
    @Fast-Nop The range is supposed to be 3 to 12 volts +/-. My guess is it might be more of a current sourcing issue. I know laptops had this issue. So resistors fucking it up, yeah, shit buy a different one. Wait I have bought 10 of these piece of shit adapters...
  • 3
    @Demolishun 3V level at the receiving end, that is, not on the line. With the series resistor stuff, 5V on the line were reduced into the no-man's land of around 2V at the receiving chip.
  • 1
    @Fast-Nop Thanks for the clarification.
  • 3
    @frogstair It really was the last thing to come to my mind. But the delivery company was runing a week late and I needed the adaptor for a proyect for which the deadline was getting dangerously close.
    The delivery company kept reporting that I was not home, even when while working from home due to the pandemic, I do not leave my home on weekdays... what is more, the window from where I work is 2m away from my door....
    So I went, i bought one and sincerelly told the delivery company to go fuck demselves.
    Their customer service even told me that "although they didn't want to imply that I lied, it was my word agains the delivery guy"
    It goes without saying that I will never work with them again....
  • 2
    @Fast-Nop that really is usefull to know. I'll have it in mind. Thak you!! :)

    Luckily the adaptor I ended up buying worked like a charm with the device I had to use.
  • 1

    I'm reminded when I got a new bicycle, that needed new innertubes..

    So, rather than buy them off the internet and get the wrong ones. (Since 24" no longer means one size, there are two 24" sizes..)

    I went instead to a cycle store..

    Got home, thought they looked not quite the right size, but hey, the experts told me they was, so..

    Put them in, pumped them up..

    A few hours later, loud bang noises..

    No, they wasn't the right size..

    After much asking in online forums, I discovered there was now several standards, and you can't just ask for a 24" tube.. (Or even rely on what it says on the tyre..)

    So, now I ask a bunch of folk these kind of questions !

    Which, when half give you one answer and the other half give you a different answer, makes it just as difficult to figure out which half is right !
  • 0
    I had a lot of issues with RS232 adapters over the years..

    I won't even go into the issues of PCI to USB adapters, which I also had issues with !

    There, it was something like, they would work fine in PCI 2.0a boards, but not PCI 3 boards..

    Anyhow, back to USB to RS232 adapters, which I started to buy to find one that worked..

    (I never did find one to work, I gave up when they got to $100 each !)

    But I did find out years later, which one I should have got !

    And kinda why..

    I think these are the ones recommended to me that actually work:

  • 0
    Stuff someone said about the issue:


    Most modern pc's & laptops no longer have RS232 connectors. In this case you will need to use a USB to serial adapter. Very few (if any) of the cheaper ones will work. Adapters with the Prolific PL2303HXD Revision D Chipset are known to work, so look for adapters with that chipset. You will still need a female to female null modem cable to use with these adapters, as the adapters simulate a genuine RS232 connector which is male. Don't use a gender changer on the adapter as it won't work.

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