Serial Communication

Serial Communication in LabVIEW

Wikipedia and other sources provide a sound foundation for learning serial communication.  This page describes some of the nuances with serial communication in the test and measurement world and specifically with using LabVIEW.

USB to Serial Converters

Modern computers long ago stopped shipping with serial ports, but that hasn't stopped serial communicaiton from being used.  CanyonSleeper uses serial communication freqeuntly, usually using USB to Serial converters.  Here are a few of our take-aways:

• Some USB to Serial Converters will show up as a different COM Port when the unplugged, when the computer reboots, or at other times.  This can cause problems with computer programs that depend on a particular COM port being assigned.  One reason it may be worth it to pay for NI's expensive serial devices is that they've made sure the COM Port will stay consistent after shutting the computer down, plugging in different devices, etc.

• CanyonSleeper and some of its clients have old Radio Shack USB to serial converters around.  These work great from a hardware perspective, but they can be difficult to find drivers for.  Windows update won't find and automatically install these drivers. Installing the drivers from a network location fails; the drivers must be copied to a local disk for Windows Hardware Manager to install them correctly.

• Adapters can be found for both RS232, RS485/RS422, etc.  Be careful to make sure you have the right adapter; we've found that RS485 will successfully write to RS232, but reading from RS232 will result in a framing error or other error (Error -1073807298 was recently seen)

• NI has a useful application (NI IO Trace)  for monitoring serial messages sent to and from any devices using NI's communication software (NI-VISA).