lesson6.html

tinyos中文手册,是根据tinyos系统自带手册翻译过来的,虽然质量不好,但是对英文不强的人还是有用的

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      <td width="100%"><b><font face="arial,helvetica">Starting the
Oscilloscope GUI</font></b></td>
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</table>
</p>
<p>It is now time to graphically display the data coming from the
motes. Leaving the serial forwarder running, execute the command </p>
<pre>&nbsp; java net.tinyos.oscope.oscilloscope</pre>
This will pop up a window containing a graphical display of the sensor
readings from the mote (If you get an error like "port COM1 busy", you
probably forgot to unset the MOTECOM environment variable at the end of
the Listen example. Do that now). It connects to the serial forwarder
over the network and retrieves packet data, parses the sensor readings
from each packet, and draws it on the graph:
<center>
<p><img width="600" height="600" border="0" src="imgs/oscilloscope.JPG"></p>
</center>
<p>The <i>x</i>-axis of the graph is the packet counter number and the
<i>y</i>-axis
is the sensor light reading. If the mote has been running for a while,
its packet counter might be quite large, so the readings might not
appear on the graph; just power-cycle the mote to reset its packet
counter to 0. If you don't see any light readings on the display, try
zooming out on the Y axis (the values might be out of the displayed
range) or selecting the "Scrolling" push button (the sample number may
be out of the displayed range, "Scrolling" automatically scrolls to the
most recent values).<br>
&nbsp;
<table hspace="4" width="100%" cellpadding="3" cellspacing="2"
 border="0">
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    <tr bgcolor="#e0e0ff">
      <td width="100%"><b><font face="arial,helvetica">Using MIG to
communicate with motes</font></b></td>
    </tr>
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</p>
<p><a href="../../nesc/doc/mig.html">MIG (Message Interface Generator)</a>
is a tool that is used to automatically generate Java classes that
correspond to Active Message types that you use in your mote
applications. MIG reads in the nesC <tt>struct</tt> definitions for
message types in your mote application and generates a Java class for
each message type that takes care of the gritty details of packing and
unpacking fields in the message's byte format. Using MIG saves you from
the trouble of parsing message formats in your Java application. </p>
<p>MIG is used in conjunction with the <tt><a
 href="../../tools/java/net/tinyos/message">net.tinyos.message</a></tt>
package, which provides a number of routines for sending and receiving
messages through the MIG-generated message classes. <tt><a
 href="../../nesc/doc/ncg.html">NCG(nesC Constant Generator)</a></tt>
is
a tool to extract constants from nesC files for use with other
applications and is typically used in conjunction with <tt>MIG</tt>. </p>
<p>Let's look at the code from <tt><a
 href="../../tools/java/net/tinyos/oscope/GraphPanel.java">tools/java/net/tinyos/oscope/GraphPanel.java</a></tt>
(part of the <tt>oscilloscope</tt> program) that communicates with the
serial forwarder. First, the program connects to the serial forwarder
and registers a handler to be invoked when a packet arrives. All of
this
is done through the <tt><a
 href="../../tools/java/net/tinyos/message/MoteIF.java">net.tinyos.message.MoteIF</a></tt>
interface: </p>
<center>
<table hspace="4" width="80%" cellpadding="3" cellspacing="2" border="0">
  <tbody>
    <tr bgcolor="#e0e0e0">
      <td width="100%"><b>GraphPanel.java</b>
      <pre>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; // OK, connect to the serial forwarder and start receiving data<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mote = new MoteIF(PrintStreamMessenger.err, oscilloscope.group_id);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mote.registerListener(new OscopeMsg(), this);</pre>
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</center>
<p><tt>MoteIF</tt> represents a Java interface for sending and
receiving
messages to and from motes. The host and port number of the serial
forwarder are obtained from the environment variable <tt>MOTECOM</tt>.
You initialize <tt>MoteIF</tt> with&nbsp; <tt><a
 href="../../tools/java/net/tinyos/util/PrintStreamMessenger.java">PrintStreamMessenger</a></tt>
which indicates where to send status messages (<tt>System.err</tt>), as
well as an (optional) Active Message group ID. This group ID must
correspond to the group ID used by your motes. </p>
<p>We register a message listener (<tt>this</tt>) for the message type <tt>OscopeMsg</tt>.<tt>OscopeMsg</tt>
is automatically generated by <tt>MIG</tt> from the nesC definition
for <tt>struct
OscopeMsg</tt>, which we saw earlier in <tt>OscopeMsg.h</tt>. Look at <tt><a
 href="../../tools/java/net/tinyos/oscope/Makefile">tools/java/net/tinyos/oscope/Makefile</a></tt>
for an example of how this class is generated. You will see: </p>
<pre>&nbsp; OscopeMsg.java:<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; $(MIG) -java-classname=$(PACKAGE).OscopeMsg $(APP)/OscopeMsg.h OscopeMsg -o $@</pre>
Essentially, this generates <tt>OscopeMsg.java</tt> from the message
type <tt>struct OscopeMsg</tt> in the header file <a
 href="../../apps/Oscilloscope/OscopeMsg.h">apps<tt>/Oscilloscope/OscopeMsg.h</tt></a>.
<p><tt>GraphPanel</tt> implements the <tt>MessageListener</tt>
interface, which defines the interface for receiving messages from the
serial forwarder. Each time a message of the appropriate type is
received, the <tt>messageReceived()</tt> method is invoked in <tt>GraphPanel</tt>.
It looks like this: </p>
<center>
<table hspace="4" width="80%" cellpadding="3" cellspacing="2" border="0">
  <tbody>
    <tr bgcolor="#e0e0e0">
      <td width="100%"><b>GraphPanel.java</b>
      <pre>  public void messageReceived(int dest_addr, Message msg) {<br>    if (msg instanceof OscopeMsg) {<br>      oscopeReceived( dest_addr, (OscopeMsg)msg);<br>    } else {<br>      throw new RuntimeException("messageReceived: Got bad message type: "+msg);<br>    }<br>  }<br><br>  public void oscopeReceived(int dest_addr, OscopeMsg omsg) {<br>    boolean foundPlot = false;<br>    int moteID, packetNum, channelID, channel = -1, i;<br><br>    moteID = omsg.get_sourceMoteID();<br>    channelID = omsg.get_channel();<br>    packetNum = omsg.get_lastSampleNumber();<br>&nbsp;&nbsp;  <br>&nbsp;&nbsp;&nbsp; /* ... */</pre>
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<p><tt>messageReceived()</tt> is called with two arguments: the
destination address of the packet, and the message itself (<tt>net.tinyos.message.Message</tt>).<tt>Message</tt>
is just the base class for the application-defined message types; in
this case we want to cast it to <tt>OscopeMsg</tt> which represents
the
actual message format we are using here. </p>
<p>Once we have the <tt>OscopeMsg</tt> we can extract fields from it
using the handy <tt>get_sourceMoteID()</tt>, <tt>get_lastSampleNumber()</tt>,
and <tt>get_channel()</tt> methods. If we look at <tt>struct OscopeMsg</tt>
in <tt>OscopeMsg.h</tt> we'll see that each of these methods
corresponds
to a field in the message type: </p>
<center>
<table hspace="4" width="80%" cellpadding="3" cellspacing="2" border="0">
  <tbody>
    <tr bgcolor="#e0e0e0">
      <td width="100%"><b>OscopeMsg.h</b>
      <pre>struct OscopeMsg<br>{<br>&nbsp;&nbsp;&nbsp; uint16_t sourceMoteID;<br>&nbsp;&nbsp;&nbsp; uint16_t lastSampleNumber;<br>&nbsp;&nbsp;&nbsp; uint16_t channel;<br>&nbsp;&nbsp;&nbsp; uint16_t data[BUFFER_SIZE];<br>};</pre>
      </td>
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</center>
<p>Each field in a MIG-generated class has at least eight methods
associated with it: </p>
<ul>
  <li> <tt>isSigned_<i>fieldname</i></tt> - Indicates whether or not
this field is a signed quantity.</li>
  <li> <tt>isArray_<i>fieldname</i></tt> - Indicates whether or not
this
field is an array.</li>
  <li> <tt>get_<i>fieldname</i></tt> - Return the value of this field.</li>
  <li> <tt>set_<i>fieldname</i></tt> - Set the value of this field.</li>
  <li> <tt>offset_<i>fieldname</i></tt> - Return the offset (in bytes)
for this field.</li>
  <li> <tt>offsetBits_<i>fieldname</i></tt> - Return the offset (in
bits) for this field.</li>
  <li> <tt>size_<i>fieldname</i></tt> - Return the length (in bytes)
of
this field.</li>
  <li> <tt>sizeBits_<i>fieldname</i></tt> - Return the length (in
bits)
of this field.</li>
</ul>
Note that additional methods are generated for fields that are arrays.<br>
<p>The remainder of <tt>messageReceived()</tt> pulls the sensor
readings out of the message and places them on the graph.
<table hspace="4" width="100%" cellpadding="3" cellspacing="2"
 border="0">
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    <tr bgcolor="#e0e0ff">
      <td width="100%"><b><font face="arial,helvetica">Sending a
message through MIG</font></b></td>
    </tr>
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</p>
<p>It is also possible to send a message to the motes using MIG. The <tt>Oscilloscope</tt>
application sends messages of type <tt>AM_OSCOPERESETMSG</tt>, which
causes the mote to reset its packet counter. Looking at <tt>clear_data()</tt>
in <tt>GraphPanel.java</tt>, we see how messages are sent to the
motes: </p>
<center>
<table hspace="4" width="80%" cellpadding="3" cellspacing="2" border="0">
  <tbody>
    <tr bgcolor="#e0e0e0">
      <td width="100%"><b>GraphPanel.java</b>
      <pre>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; try {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; mote.send(MoteIF.TOS_BCAST_ADDR, new OscopeResetMsg());<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; } catch (IOException ioe) {<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; System.err.println("Warning: Got IOException sending reset message: "+ioe);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ioe.printStackTrace();<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; }</pre>
      </td>
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</center>
<p>All we need to do is invoke <tt>MoteIF.send()</tt> with the
destination address and the message that we wish to send. Here, <tt>MoteIF.TOS_BCAST_ADDR</tt>
is used to represent the broadcast destination address, which is
identical to <tt>TOS_BCAST_ADDR</tt> used in the nesC code. <br>
&nbsp;
<table hspace="4" width="100%" cellpadding="3" cellspacing="2"
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    <tr bgcolor="#e0e0ff">
      <td width="100%"><b><nobr><font face="arial,helvetica">Exercises</font></nobr></b></td>
    </tr>
  </tbody>
</table>
</p>
<p>Transmit the light sensor readings over the radio to another mote
that sends them over the serial port! </p>
<p>The <tt>apps/Oscilloscope</tt> mote application is written to use
the serial port and the light sensor. Instead, look at <tt><a
 href="../../apps/OscilloscopeRF">apps/OscillosopeRF</a></tt>, which
transmits the sensor readings over the radio. In order to use this
application, you need to use one mote as a gateway that receives data
packets over the radio and transmits them over the serial port. <tt><a
 href="../../apps/TOSBase">apps/TOSBase</a></tt> is an application that
does this; it simply forwards packets between the radio and the UART
(in
both directions). </p>
<p><b>Extra Credit</b>: Can you figure out how to display sensor
readings on the oscilloscope GUI from two motes simultaneously? (Note
that the oscillosope GUI is already capable of displaying sensor
readings from multiple motes. You have to ensure that those readings
are
correctly transmitted and received over the network.) This setup would
look like the following diagram. </p>
<center>
<p><img width="720" height="540" src="imgs/Serial_Forward_topology.jpg"></p>
</center>
<p> </p>
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