Serial Port Support

The maximum number of serial ports that NI-VISA currently supports on any platform is 256. The default numbering of serial ports is system dependent, as shown in the following table.

How Serial Ports Are Numbered

Platform Method
Windows 7/Vista/XP/Server 2008 R2/Server 2003 R2 All COM and LPT ports are automatically detected when you call viFindRsrc(). The VISA interface number may not equal the COM port number.
LabVIEW RT All COM ports are automatically detected when you call viFindRsrc().
LabVIEW PDA All COM ports are automatically detected when you call viFindRsrc().
Mac OS X All COM ports are automatically detected when you call viFindRsrc().
Linux ASRL1-ASRL4 access /dev/ttyS0 – /dev/ttyS3.

If you need to know programmatically which ASRL INSTR resource maps to which underlying Serial port, the following code will retrieve and display that information.

 C example

 Visual Basic example