Modsoft in VMWare

I am trying to get Modsoft running inside a VMWare image and have been unable to get it to communicate over the serial port with a controller.

Having tried to access the controller from a different machine, it all works fine.

The VMWare image has Windows 95 on it, with just Modsoft installed, currently running on a Windows XP Pro host machine.

When I attempt to connect to the controller, I get a flash on the controller's lights, but nothing more.

I have tried forcing the parity, flow control, data rate etc. on the serial ports on both the host and the guest, but this made no diference.

I tried mapping the output from the serial port from the guest OS to a file on the host and this showed that there was something getting out of the guest OS (although it did appear as a random set of characters - not sure what it should look like).

I have looked around quite extensively to figure this one, and have come out with a couple of possible issues, but I've very little knowledge about Modsoft / Modbus and couldn't confirm them. These where:
1)Maybe non-standard pins were being used on the cable that were not being emulated and passed through by VMWare.
2)The host OS (Windows XP) maybe 'intercepting' the data and altering it in some way.

Can anyone confirm or remove either of these?

Has anyone been able to get modsoft running correctly inside a virtual machine, talking out over the serial port?

Any ideas what I'm doing wrong?

Thanks

Modbus RTU is very timing dependent.

If you look at the Modbus RTU specifications you will see that Modbus RTU requires that the time between the characters is no more than 1.5 character times and a new message starts with 3.5 character times. At 9600 baud a character time is about 1 millisecond so this timing is very fine considering the Windows doesn't have a good ways of checking this small timing intervals.

Now you have added VMWare and made checking the time between characters even more difficult. I would try DOS in a VM.

I do not like Modbus RTU because few other products we come across come close to timing specifications but we still get calls similar to this one when the customer can't talk to our controller.

It is difficult to impossible to meet the Modbus timing specificaitons unless there are timers dedicated just to checking the time between characters.

Peter,

thanks for the info.

I have put together a VM with just DOS and Modsoft, but sadly I'm still getting exactly the same results.

Any other suggestions?

(feeling like its a lost cause...)

Dan,

What Modicon CPU are you using?

At the moment, we've been trying to get it working with a 984 385E controller, but we have seem to have one of almost all of the Modicon range laying around... and eventually we will need to get up and running with it all in VMWare - this is just the first 'trial'

Hi Dan,

As Peter says above, RTU timing requirements are very stringent, so you'll have more chance of success connecting in ASCII mode rather than RTU mode.

In Modsoft you change this via: Offline - Change PLC Address - Mode -

Across the Modicon range there are various options and methods for changing the Modbus port to ASCII mode but for starters here's an extract from the manual of the 984-385E controller...


Kevin H

just an after thought...if your not totally committed to VMware and just want to run Modsoft under WinXP, then we use products from this company...

http://www.cyberlogic.com/mbxdriversuite.htm

Look at the virtual & serial MBX drivers.


Kevin H