Need help with serial port please

[David]

I have written an application in VB.NET 2003 that uses the SAX serial
component for RS232 communications with hardware.

The program sets up 2 serial ports so that it can talk to 2 different
hardware devices simultaneaously.

When I run the program on a desktop running Windows 2000 it works fine. When
I run it on a Laptop using XP I start having problems.

It seems that when the ports are initiated, either one will work but not the
other.

Can someone please show me an example of the correct way to set up the
serial ports using the SAX component and any gotchas I may have overlooked.

Thanks in advance

 

[Thomas Lutz]

It may be the serial port hardware that you are having a problem with.
Does the laptop have two built in COM ports or are you using some sort
of add-on adapter?
Serial port hardware uses a hardware interrupt (IRQ) and in some cases
each serial port must have its own interrupt line.
If you do not have enough free IRQ lines in your PC or if the driver
software for your add-on adapter cannot address all of the free IRQ
lines then the two ports may be using the same IRQ and Windows will
not allow you to open both ports at the same time because of a "IRQ
Conflict".
You might try getting a multi port add-on serial adapter that connects
to the USB port on your PC. With these types of adapters, you do not
need to worry about "conflicts" because all ports use the same USB
IRQ.
You should be able to find USB add on serial adapters at any computer
supply store or you can also find them at:
http://www.taltech.com/products/rs232.html