RS-232 Port Problem

[stu54]

I am trying to use the RS-232 port. I do have console out turned off in the NI web-based tool. Here is my init code in the constructor:

serial = new SerialPort( 9600, SerialPort.Port.kOnboard );

Then in my loop in operatorControl() I have:

String ss = serial.readString();

And that causes this trace on the driver station console:

ERROR Unhandled exception: java.lang.RuntimeException: Code: -1073807298. HAL - VISA: General IO Error at [edu.wpi.first.wpilibj.hal.HALUtil.checkStatus(HALU til.java:48), edu.wpi.first.wpilibj.SerialPort.getBytesReceived( SerialPort.java:326), ...


I get the same traceback even if I have nothing connected to the
RS-232 port.

Any ideas?