[slibert]

Originally Posted by tech2077

I was trying to run the posted code in order to test out the serial port on our cRIO. The code faulted with a null pointer error due to the serial resource not being initialized and returning the error "VI_ERROR_RSRC_NFOUND in function viOpen"

import edu.wpi.first.wpilibj.IterativeRobot;
import edu.wpi.first.wpilibj.SerialPort;
import edu.wpi.first.wpilibj.visa.VisaException;

public class RobotTemplate extends IterativeRobot {
    
    public SerialPort serial;
    
    public void robotInit() {
    }
    public void autonomousInit() {
    }
    public void autonomousPeriodic() {
    }
    
    public void teleopInit() {
        try {
            serial = new SerialPort(115200);
        } catch (VisaException ex) {
            System.out.println("Error to initialize serial port at 115200 baud " + ex.getMessage());
        }
    }
    
    public void teleopPeriodic() {
        try {
            serial.print("test");
            System.out.println(serial.read(1));
        } catch (VisaException ex) {
            System.out.println("Error");
        }
    }
}

I'm working with a few teams who are using the nav6 IMU, and they are running into this problem too.

It's sporadic.

SerialPort settings we use are 57600, 8, N, 1

The nav6 sends a stream of 30-40 bytes packets at about 20-50Hz rate, so a stream of bytes is arriving when the serial port is opened.

[cRIO] edu.wpi.first.wpilibj.visa.VisaException: VI_ERROR_RSRC_NFOUND in function viOpen
[cRIO] at edu.wpi.first.wpilibj.visa.Visa.assertCleanStatus( Visa.java:151)
[cRIO] at edu.wpi.first.wpilibj.visa.Visa.viOpen(Visa.java:6 3)

Here's a note on the error:

"...there doesn't seem to be any consistency with when the error occurs. Occasionally it would happen after a few times of sending new code to the robot and sometimes it would happen after I had just powered on the robot. I wasn't able to find anything that seemed to be a specific trigger. I was typically able to fix it by leaving the robot powered off for a period of time and then powering it back on."

[Side Note: If possible, if the Java SerialPort class is being modified, can the setReadBufferSize() method please be made public?]