Serial Command Sent with XP machine different than sent with WIN2000 machine

[Terry_S]

I need to communicate with a device by sending a Hexadecimal command (AA00 0000).  I am using Portnom to watch what is being sent to the serial port.  When I run my VI on a Windows 2000 computer my command is being wrote to the port and the instrument sends back the requested information.  However when I run the same VI on a WindowsXP machine the lenght is the same (4 bytes) but four dots are being displayed as what is being sent and there is no response from the instrument.  I am running LabView 7.1 on both machines.  Any help would be great.

[Greycat]

Have you intialized the port to a particular baud rate in the vi?  I assume you are using Com 1? 

Greycat

[Terry_S]

Yes I have. 

[Greycat]

Can you verify the baud rate at which it is actually being sent?  Does Portmon do that?  Sounds like a baud rate issue (that is my first instinct), but if you can verify the actual baud rate then you will know that it is not that problem.  Anyway you could have a look at the actual bits being sent?  Just some ideas ...

Greycat

[unclebump]

Portmon data should show all of the port setting info and the data transfer. Start the portmon capture before you open each comm programs. Save the data for both comm programs. There may be some portmon options that have to be changed.

[Terry_S]

Yes,  I have verified with PortMon that the comm settings are the same on both machines.

[AnalogKid2DigitalMan]

Are you using the same physical instrument and cable for both machines? (Instrument settings or cable wiring possibly different?)

[Terry_S]

I am fortunate to have both machines sitting side by side, so I simply move the cable from one machine to the other.  The only difference is the XP machine is a laptop.

[AnalogKid2DigitalMan]

Same versions of NI software, especially VISA drivers and MAX?

Is it a pure serial port on the laptop or a USB to serial converter?

What is MAX showing for the name of the COM ports, sometimes a laptops port is not always COM1

Any errors being flagged within the error piping in your vi?

Have you tried to use Windows Hyperterminal on both PC's, this should eliminate any potential differences in NI software and configurations.

Proper grounding of the instrument ?

A lot of questions, I know.

Message Edited by AnalogKid2DigitalMan on 02-22-2006 11:46 AM