Confused serial ports win7 host win 98 guest

[sam99517]

Hi

Apologies if the answer is buried in the forum already someone - I've tried searching and following some but I'm not too technical so I can't be sure I've understood!

I have an old piece of lab equipment tech using a DB25 serial port. The software to run it won't work on anything newer than win 98

I don't have a win98 PC with a serial port, so I have an old win 7 PC with a USB to RS232 DB9/DB25 adaptor from startech. Annoyingly the startech adaptor works on win XP and newer not 98 - which makes it complicated

The USB to DB25 is installed and happy on the win7 host. I configured a win 98 guest with serial ports that "should" let it see that com port and use the win98 software to talk to the machine, but I can't get it to see the equipment!

Any help/advice would be appreciated - see pics to see if I have configured correctly!

Win 7 dev man and guest setup

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win 7 dev man and win 98 dev man

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You'll be saving a broke research lab a few grand if there's a solution!

Thanks

[scottgus1]

USB to DB25 is installed and happy on the win7 host

Does this device have drivers for Windows 98? If so, it may be easier to let the 98 VM directly control it using a Virtualbox USB filter. See USB basics and troubleshooting.

It does look like you have a good serial setup. The COM3 device on the host appears to come in on the VM as COM1. I see that you have a COM3 device on the VM as well. What is that?

[sam99517]

Thanks for looking, no the USB to DB25 needs to be on win xp or later. I tried to install anyway on the win98 guest and it just crashes!

The COM3 on the guest was because I thought you had to make COM3 on the host pass to COM3 on the guest, until I found a post that said this was unnecessary. The other tabs of the guest virtual box serial ports settings (ports 2, 3, 4) are all deactivated now but COM3 remains in win98 dev manager. Interestingly the equipment software complains it can't open COM3 (or COM2/4 if I ask it to look there for the hell of it) but doesn't complain for COM1, but still fails to find the machine.

[scottgus1]

I'm no serial guru, but there may be a way to use 98's HyperTerminal to test the serial channel.

[mpack]

You have to be very careful with USB serial adapters: basically you can never unplug them from the host USB port while the VM is running, because they will not be automatically recovered when you plug them back in. As far as Windows is concerned that's a whole new and different serial port.

The other thing is that I'm not happy to see the Prolific name there. Don't misunderstand, Prolific itself is fine - but there are a lot of cheap fake Prolific adapters out there with crappy and sometimes obsolete drivers. Though probably not obsolete on a Win7 host.

[sam99517]

I'm no serial guru, but there may be a way to use 98's HyperTerminal to test the serial channel.

Sorry took me a while to get the chance to try/work out how!

As far as I can tell its working - win 98 hyperterminal doesn't repeat what i sent apparently but if I remove the foil jammed in there I get nothing back.

hyperterminal com test results

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The other thing is that I'm not happy to see the Prolific name there. Don't misunderstand, Prolific itself is fine - but there are a lot of cheap fake Prolific adapters out there with crappy and sometimes obsolete drivers. Though probably not obsolete on a Win7 host.

I believe the test @scottgus1 recommended proves it should be ok? It came from a company called startech that seem reputable...

So if the usb com port is working then the other option is I dont have the correct settings required to communicate with the machine. The documentation seems clear on what it wants and I've set this in both windows 7 device manager and win 98 device manager. Could there be some incompatibility by having both the host and guest doing weird things (whatever xon/off flow controls for example) - perhaps the host/guest need to be configured differently from each other?

Instructions from documentation

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com port settings

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[scottgus1]

As far as I understand, Serial is not sharable. So there would be no need to match the host's settings to the VM. And the host cannot have an app trying to access the serial port while the VM is trying.

I honestly don't know if the foil jumper shows positive results, that's way beyond my awareness of serial activity. But I did note that you mentioned a "USB to DB25" adapter. That plug in the picture is a DB9. Are you sure you're testing the correct adapter?

[sam99517]

As far as I understand, Serial is not sharable. So there would be no need to match the host's settings to the VM. And the host cannot have an app trying to access the serial port while the VM is trying.

I honestly don't know if the foil jumper shows positive results, that's way beyond my awareness of serial activity. But I did note that you mentioned a "USB to DB25" adapter. That plug in the picture is a DB9. Are you sure you're testing the correct adapter?

Yeah I was just too lazy to look up which pins to use for the DB25, turns out its the same ones. The USB adaptor comes with a db9 to db25 adaptor and that works fine too by coms

db9 to db25 adaptor

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db25 com test result

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Thanks for your help anyway with this

[scottgus1]

An idea pops in: You have a Windows 7 host. If you're running Virtualbox 7.0, Windows 7 is no longer a supported host OS.

You could try a version towards the end of 6.0 or 5.2, see https://www.virtualbox.org/wiki/Download_Old_Builds just in case a serial bug has crept in, or a host OS incompatibility is present.

[sam99517]

I'm already on 5.2.44 - tried installing the latest version originally but it wanted some libraries that were a pain to download and transfer manually (this host is non networked), and may not have worked anyway

Think 5.2.44 was the newest I found that still had win 7 support but I'll scroll through and look for other versions to see if that helps thanks

[scottgus1]

I suspect that 5.2 should be working just fine. This could be some other issue with the software's needs. Here's an idea:

I surmise that serial should just be serial, regardless of the age of the OS running it. Probably a massive over-simplification, but walk with me a minute... So if one could get two computers connected through serial (via a null modem cable?) and use Hyperterminal on each, then one should be able to arrange to type stuff on one terminal and it would appear on the other. Basic old-school teletype stuff. There should be tutorials on how to do this on the web.

If you could do that between the VM and another PC with a serial port and get characters passing through, it would seem that the Virtualbox serial setup would be working, showing that the problem would be in the special software's needs.

Maybe...?