USB 232/4 and interrupt event

[mike72903]

We recently got a new laptop to run some automated calibration routines written in VB6.  The new laptop did not have a PCMCIA slot so we purchased a USB 232/4 box from NI. All four ports are connected to different pieces of equipment and all but one work properly.  The one that does not work properly is the only one of the four that is using a VB ON_COMM event.  An instrument is sending data at 10 second intervals that triggers the on comm event.  The event executes but generates  ERR 424 in VB.  This program previously worked well on a laptop with an NI 4 port PCMCIA card and previous to that, a desktop with 4 comm ports.  Is something going on with the USB converter that's would cause this?  Not sure what to consider next.  MS help shows error 424 is a server error?  Any help appreciated.  Thanks

[_enigma_]

Mike,

You should not be having any problems using Visual Basic and the USB 232/4 to communicate with your serial device.

I would first check the communication in the Measurement and Automation Explorer (MAX), which was included in the NI-VISA installation.  If you are able to communicate with your device, then the code implemented in Visual Basic is most likely causing the error.  If you are unable to communicate with your device, and you have tried all four serial ports, a number of issues could be present.

Double check you are able to communicate with your device using MAX, then take a look at the article below:

Serial Communication in Visual Basic

Regards,

Alexander M   ||   Applications Engineer   ||   National Instruments