serial port problem

[Alan@pworx]

Every time I reboot my computer (i7) I have a serial port problem. Checking the Windows device driver reveals no problem, but when I open MAX there is a caution on the COM1 icon and the validate test fails with an unknown error. If I go back to the Windows device manager and update the comm port driver, then go back to MAX the com port works and is fine until I reboot the computer. This happens on all systems that we have set up using both XP and Win7 and using the coms port header on the motherboard with no additional hardware plugged in and no other specific software running. Systems running LV 8.5 and 2010 have the same problem. The com port is set to 38400 baud, 8 data bits, no parity, 1 stop bit, and no flow control.

[Anna_K.]

Hello, what version of VISA do you have installed? Give the steps in this KB a try:

COM Port in MAX Shows Exclamation Point

Thanks,

Anna K.

[Alan@pworx]

Hi Anna, I'm using the LV 2010 version, but had the same problem with previous versions.

[Anna_K.]

Hello, Your version of NI VISA driver is independent of the version of LabVIEW, you can check the version in the Software section of Measurement and Automation Explorer.

Were you successful in using the Knowledge Bases that I attached?

[Alan@pworx]

Hi Anna, the VISA version is 5.0. I need to revise my initial statement. Win7 & LV 2010 always fails COM1 on a reboot, but WinXP & LV 8.5 is more haphazard -it doesn't always fail COM1 on a reboot, but can also fail without rebooting with no obvious sequence of events. Our production systems (they all fail periodically) are simplistic in setup -there is no fancy software in the background, and no antivirus: they are standard WinXP and Win7 installations and the only extra software is Adobe Acrobat reader, so there is nothing strange about the system software. The COM1 port is connected to a simple 2-wire device.

The Knowledge Bases do not cover the problem I'm experiencing.

[Alan@pworx]

Hi Anna, The older WinXP and Win7 systems have LV 8.5 executables with VISA 4.2. At this stage it is only my development system running Win7 with LV 2010 and VISA 5.0.

[Wayne.C]

Alan,

I have seen a situation where having a COM port connected to a powered device during computer reboot can cause problems.  Has something to do with COM port/driver expecting to see a certain condition on RX/TX lines at power up.  What kind of device/s is your port connected to?

[Alan@pworx]

Hi Wayne, we are connected to a device that uses Max-232 or Sipex chipsets. Our production models have a built-in Intel mico-ATX motherboard with a Serial Port header which boots up slightly after our controller with the RS-232 port. The system has a power switch that gives immediate power to our controller and the motherboard power supply, after which a button has to be pressed in order to boot the PC. Only Com Port pins 2,3, and 5 are used and there is no flow control selected.

[Wayne.C]

Alan,

This sounds like a problem at the hardware level.  A couple of suggestions that might help identify the culprit and point to a permanent fix.

1. Break serial connection between PC and controller during powerup sequence.  After both are up and running, make serial connection.
2. Put an o-scope on the RX/TX lines of COM port and monitor during the powerup sequence.  Might see something interesting.
3. Try using a port powered RS232 isolator between PC and controller.
4. Alter the powerup sequence of the PC and the controller. I realize that the altered sequence most likely is not a final fix but may help point to/verify the problem.

[Alan@pworx]

Thanks Wayne, I'll give it a try.