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S ERIAL C OMMUNICATION U SING VARIOUS P ROGRAMMING L ANGUAGES
This file defines two classes named AnalogReader and AnalogReaderTest.
AnalogReader actually encapsulates access to the Arduino. It stores an
InputStream object in _input to receive data, and it stores an OutputStream
object in _output to send data to the Arduino.
The constructor initializes the serial port connection and assigns its
input and output streams to our member variables. To obtain a serial
port connection, we have to get a CommPortIdentifier object first. From
this object, we can then create a SerialPort object. This object gives us
access to the underlying streams, and it also allows us to set the port’s
parameters, such as the baud rate.
We implement the protocol for our Arduino sketch in the run( ) method.
There we wait for two seconds, and then we start a loop. In the loop,
we send the string “a0” to the serial port using OutputStream’s write( )
method. Before we send the string, we turn it into a byte array calling
getBytes( ). To give the Arduino some time to create a result, we wait for
another 100 milliseconds. Afterward, we check if a result is available
and read it by invoking InputStream’s read( ) method.
AnalogReaderTest is only a small driver class that implements a main( )
method, creates an AnalogReader object, and calls run( ) on it. Here’s
how to compile and use the program:
maik> javac AnalogReaderTest.java
maik> java AnalogReaderTest /dev/tty.usbmodemfa141
Experimental: JNI_OnLoad called.
Stable Library
=========================================
Native lib Version = RXTX-2.1-7
Java lib Version
= RXTX-2.1-7
a0: 496
a0: 433
a0: 328
a0: 328
^C
After some debug output from the libraries we are using, the AnalogReaderTest does exactly what it’s intended to do: it permanently prints
the values of the analog pin 0. Accessing a serial port in Java is a piece
of cake if you use the right libraries.
Ruby
Even dynamic languages such as Ruby give you instant access to your
computer’s serial port and to an Arduino if you connect it to it. But
before that, you need to install the serialport gem:
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this copy is (P1.0 printing, Janurary, 2011)
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