communications problem with Lookout 6.0.1 and radio modem

[Txkmarty]

I just upgraded a customer with Lookout 6.0.1 and a new Dell with XP. We're communicating with several remote sites via radio modem at 300 baud. (Old radios but usually reliable) We upgraded from 4.0.1 on an E-Machine that prerformed OK, not great, but OK. I had to tinker with the serial port settings to get any comm at all, and even then it was hit & miss. About 20 hours in, and within about a 10 minute window, seven of the nine sites dropped communications.  I can adjust the  settings and pick up an occasional good comm, but for the most part they're all no response, or garbled.
We have an old Compaq lap-top with WIN98 and  a 3.8 version of Lookout sitting beside the new computer.
Even with little or no comm on the new unit I can plug the comm line to the lap-top and have almost pefect communications. So in my mind that would eliminate the radio or other hardware as a problem.
Of course the E-machine we just replaced also ran XP, and while it wasn't as reliable as the lap-top it worked acceptably.
I even installed the old Lookout 3.8 on the new machine to try it and it wouldn't comm either.
Someone told me that XP accesses the serial port differently than WIN 98. (Something about 98 still being dos based)  Is this so, and if it is would there be any advantage in installing another serial port?
Any Ideas? I know I'm on borrowed time on this lap-top

[Paul M.]

Txkmarty,

How long is the cable run from the modem to your computer? RS232 tends to not work well above 10-15 feet or so. Also, if the cable is of a cheap build and lacks proper shielding, that could cause problems too.  The old PC's com port may have simply been more tolerant of the sub-optimal signal coming from the receiver. As the adage goes, "They don't make serial port drivers like they used to!"

You mentioned you were tweaking serial port settings -- what settings worked better than the others? What are the "proper" recommended settings?

[Txkmarty]

Paul,
Thanks for the reply. As to the cable length, I think it's just a 6' 25D / 9D factory  terminated on both ends. I could try a different cable to eliminate that as a problem. The settings (from memory. I'm not with the installation at the time)  were:
Laptop with Win98  Receive gap   80   RTS   20   CTS   100
On the new unit these settings resulted in no comm what so ever. I think I had the settings up to 500, 300, 500 or so before anything started coming in good. We adjusted this some, give or take 100ms without alot of effect one way or the other.
Can these be set too high? I assumed that high settings would only slow down the overall process a little. That isn't a major problem sense we're just filling water towers.
Do I need to try adjusting the settings more?
Is there anything to the XP vs. Win98 issue that could be causing this?
What puzzles me is the way it'll work fine for hours on end and then stop without any reason that seems apparent.

Thanks again, MC

[Paul M.]

What about your actual serial port settings? Parity/Baud Rate/Start Bits/Stop Bits could affect the performance too... What model receiver are you using? Perhaps your serial port settings changed from the other machine. How does the output look in Hyperterminal?

Also, what Lookout object are you using for communication? Modbus?

[Txkmarty]

We're using Modbus. I'm sure I checked all the serial port settings, but I'll get out to the jobsite in the next day or so and check on it. What's the possibility of getting a phone session with you when I get to the jobsite? (We purchased a support package with the software upgrade.) I know you guy's are busy, but maybe we could schedule something to save wait time at the customers expense.
Thanks, MC

[Paul M.]

MC,

Just visit ni.com/support, select the "Phone NI" option under Option 2 and answer the questions, you'll be connected to someone in our Lookout support department quickly since you have a support contract.