R232 to USB without driver on guest

Discussions about using Windows guests in VirtualBox.

R232 to USB without driver on guest

Postby rizou » 27. Jan 2023, 20:25

I'll start this by saying that I have very little experience with using serial ports. I have been trying to run VMs with Windows XP and Windows 98 to communicate with an ancient piece of hardware through R232. Unforutately my computer doesn't have serial ports, and the R232 to USB cable I have doesn't have drivers for those operating systems. It does recognize as a serial port on my host machine (W10) after installing the driver there as "COM3:". I tried configuring it as a serial port on host device like so:

SS.PNG (22.44 KiB) Viewed 987 times

I definitely have contact with the machine, but I seem to be getting some kind of loading error. The accompanying software doesn't really provide me with any logs or proper error messages. I was wondering if the way I have set up the COM port could be the issue. Is this something you would expect to work?
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Re: R232 to USB without driver on guest

Postby scottgus1 » 27. Jan 2023, 21:05

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Re: R232 to USB without driver on guest

Postby mpack » 28. Jan 2023, 12:12

Just a note about terminology: the US standard is called "Recommended Standard 232", a.k.a. RS232. The internation equivalent is called EIA-232, but the English speaking world tends to use the former. Nobody necessarily knows what you're talking about if you say "R232".

In fact, probably not many will know what "RS232" means. The FAQ that Scott refers you to doesn't mention the term. Most will refer to "serial port" or "comm port". They will say "USB to Serial Adapter", though USB-RS232 adapter is indeed more technically accurate as RS232 is only one of several kind of serial I/O (others commonly used include RS422, RS485 and USB!). RS232 is however the form of UART-serial that can be found built into many desktop PC motherboards, even if it isn't exposed on the backplane.

I think the first thing you need to do in your Win10 host is to plug in your USB adapter, then run Device Manager and expand your "Ports (COM & LPT)" branch. You should see your serial port there, and the COMn port id will be listed in parenthesis at the end. You can verify that this is the right one because it goes away when you unplug the USB device. Be warned that in Windows, comm port numbers for adapters can change if you move them around different USB ports.
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