Serial communication in Java on OS X

Question

I am trying to create a program that can both transmit and receive via a USB to serial communication. I have learned by research of two files that I will need: a .jar file containing the actual library, and from what I understand the librxtxSerial.jnilib, which is a driver?

From the following website I have learned that both of these need to be present in my project in order to begin the serial communication process.

http://rxtx.qbang.org/wiki/index.php/Download

I am using the Eclipse IDE on a mac and cannot seem to get the correct configuration of files in order to make this work. There are no clear answers anywhere on the net and I am hoping that somebody can help clear this up for everybody.

Answer 1

I've used NeuronRobotics nrjavaserial with great success on Linux and Mac OS/X. It embeds a native library into the jar file and then presents a Java interface. It is derived from RXTX and so I'm hoping it won't be a huge change for your project.

MAJOR EDIT

In the interest of saving you some time, here's what I'm doing currently. Note that I'm not using an IDE at this time - this is all command line.

import gnu.io.NRSerialPort;
import gnu.io.UnsupportedCommOperationException;

import java.io.DataInputStream;
import java.io.IOException;
import java.util.Arrays;

public class PulseOximeter {
    public static void main( String[] argv ) throws IOException, UnsupportedCommOperationException {
        NRSerialPort serial = new NRSerialPort("/dev/rfcomm0", 115200);
        serial.connect();

        DataInputStream ins = new DataInputStream(serial.getInputStream());

        // read the first 10000 bytes a byte at a time
        for( int i = 0; i < 10000; i++ ) {
            int b = ins.read();
            if( b == -1 ) {
                System.out.println( "got EOF - going to keep trying" );
                continue;
            }
        }

        serial.disconnect();
    }
}

and the maven file to build it:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>tld.domainname</groupId>
    <artifactId>bluetooth</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <properties>
        <java.min.version>1.8</java.min.version>
        <maven.min.version>3.2.0</maven.min.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <resource.directory>src/main/resources</resource.directory>
    </properties>
    <prerequisites>
        <maven>${maven.min.version}</maven>
    </prerequisites>
    <dependencies>
        <dependency>
            <groupId>com.neuronrobotics</groupId>
            <artifactId>nrjavaserial</artifactId>
            <version>3.12.0</version>
        </dependency>
    </dependencies>
    <build>
        <finalName>${project.artifactId}</finalName>
        <resources>
            <resource>
                <directory>${resource.directory}</directory>
                <filtering>true</filtering>
            </resource>
        </resources>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.3</version>
                <configuration>
                    <source>${java.min.version}</source>
                    <target>${java.min.version}</target>
                    <showDeprecation>true</showDeprecation>
                    <showWarnings>true</showWarnings>
                    <compilerArgument>-Xlint:all</compilerArgument>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

This is code for the Linux version - the biggest change will be the serial port name (the "/dev/rfcomm0") part. I don't have my Mac here so I'm sorry I forget the name of the Mac device but it is in /dev - something with Bluetooth if I remember correctly.

All this sample does is read bytes off of the serial (USB) port. Note that Java makes this a little more fun in that they come back as integers even if they are really bytes so you'll have some fun with any bit manipulations you need to do.

Answer 2

I faced the same problem a few years ago when I was setting up a Java application to receive bio-data from an arduino.

I wrestled and wrestled with the RXTX libraries and was never able to get them working properly (on both Linux and Windows). This seems to be a common problem (Stable alternative to RXTX).

My advice: move away from the RXTX libraries.

An alternative library I found that worked great and was easy to implement is the Java Simple Serial Connector (JSSC) library found at https://github.com/scream3r/java-simple-serial-connector.
And here are a few examples: http://www.javaprogrammingforums.com/java-se-api-tutorials/5603-jssc-library-easy-work-serial-ports.html

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As far as setting up in eclipse, you should be able to include the jar in the following manner:

Right click your project -> Configure Build Path -> Add External JARs -> select the jar you downloaded.
Now in package explorer you should see a "Referenced Libraries" item that, when expanded, shows the jar you added.

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Lastly, it's worth your time to look into tools like Maven or Gradle. They greatly simplify adding external libraries.

Cheers!