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12      <title>COM_ReadI2C</title>
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14      <meta name="date" content="2008-11-05">
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19<p class="header">RWTH - Mindstorms NXT Toolbox</p>
20      <div class="content">
21         <h1>COM_ReadI2C</h1>
22         <!--introduction-->
23         <p>Requests and reads sensor data via I2C from a correctly configured digital sensor.</p>
24         <!--/introduction-->
25         <h2>Contents</h2>
26         <div>
27            <ul>
28               <li><a href="#2">Syntax</a></li>
29               <li><a href="#5">Description</a></li>
30               <li><a href="#17">Example</a></li>
31               <li><a href="#20">See also</a></li>
32               <li><a href="#23">Signature</a></li>
33            </ul>
34         </div>
35         <h2>Syntax<a name="2"></a></h2>
36         <p><tt>ReturnBytes = COM_ReadI2C(Port, RequestLen, DeviceAddress, RegisterAddress)</tt></p>
37         <p><tt>ReturnBytes = COM_ReadI2C(Port, RequestLen, DeviceAddress, RegisterAddress, handle)</tt></p>
38         <h2>Description<a name="5"></a></h2>
39         <p>This function is used to retrieve data from digital sensors (like the ultrasonic) in a comfortable way. It is designed as
40            a helping function for developers wanting to access new sensors. For already implemented sensors (e.g. ultrasound, as well
41            as HiTechnic's acceleration and infrared sensors), use the provided high-level functions such as <tt>GetUltrasonic</tt>, <tt>GetInfrared</tt>, etc.
42         </p>
43         <p>For I2C communication, usually the <tt>NXT_SetInputMode</tt> command has to be used with the <tt>LOWSPEED_9V</tt> or <tt>LOWSPEED</tt> setting. Afterwards, commands can be send with <tt>NXT_LSWrite</tt>. Once a sensor is correctly working, i.e. has data available, you can use this function to retrieve them.
44         </p>
45         <p>In <tt>COM_ReadI2C(Port, RequestLen, DeviceAddress, RegisterAddress)</tt>, <tt>Port</tt> is the sensor-port the sensor is connected to. <tt>RequestLen</tt> specifies the amount of bytes you want to retrieve. For ultasound, this is 1. <tt>DeviceAddress</tt> is the sensor's address on the I2C bus. This sometimes can be changed, but not for the ultrasonic sensor. Default value is
46            0x02 (2 in decimal). Finally, <tt>RegisterAddress</tt> is the address where you want to read data from. For the ultrasound and many other sensors, the "data section" starts at
47            0x42 (66 in decimal).
48         </p>
49         <p>As last argument you can pass a valid NXT-handle to be used by this function. If no handle is passed, the default set by <tt>COM_SetDefaultNXT</tt> will be used.
50         </p>
51         <p><b>Returns:</b> <tt>ReturnBytes</tt>, byte-array (column vector) of uint8. This array contains the raw sensor-data you requested. How to interpret them depends
52            on the sensor. If communication failed (even after automatic retransmission) -- e.g. when the sensor get's disconnected while
53            in use -- an empty vector <tt>[]</tt> will be returned.
54         </p>
55         <p><b>Note:</b></p>
56         <p>Please note that the return values of this function are of type uint8. You have to convert them to double (using <tt>double()</tt>) before performing calculations with them, otherwise you might get unexpected results!
57         </p>
58         <p>The sensor you are addressing with this command has to be correctly opened and initialized of course -- otherwise no valid
59            data can be received.
60         </p>
61         <h2>Example<a name="17"></a></h2>
62         <p>This example opens and reads the ultrasonic sensor</p><pre class="codeinput">   port = SENSOR_1;
63   handle = COM_OpenNXT(<span class="string">'bluetooth.ini'</span>, <span class="string">'check'</span>);
64
65   OpenUltrasonic(port);
66
67   <span class="comment">% retrieve 1 byte from device 0x02, register 0x42</span>
68   data = COM_ReadI2C(port, 1, uint8(2), uint8(66));
69
70   <span class="keyword">if</span> isempty(data)
71       DistanceCM = -1;
72   <span class="keyword">else</span>
73       <span class="comment">% don'f forget this double()!!!</span>
74       DistanceCM = double(data(1));
75   <span class="keyword">end</span><span class="comment">%if</span>
76</pre><h2>See also<a name="20"></a></h2>
77         <p><a href="NXT_LSWrite.html">NXT_LSWrite</a>, <a href="NXT_LSRead.html">NXT_LSRead</a>, <a href="NXT_LSGetStatus.html">NXT_LSGetStatus</a>, <a href="NXT_SetInputMode.html">NXT_SetInputMode</a>, <a href="OpenUltrasonic.html">OpenUltrasonic</a>, <a href="GetUltrasonic.html">GetUltrasonic</a>, <a href="SENSOR_1.html">SENSOR_1</a>, <a href="SENSOR_2.html">SENSOR_2</a>, <a href="SENSOR_3.html">SENSOR_3</a>, <a href="SENSOR_4.html">SENSOR_4</a></p>
78         <h2>Signature<a name="23"></a></h2>
79         <div>
80            <ul>
81               <li><b>Author:</b> Linus Atorf (see AUTHORS)
82               </li>
83               <li><b>Date:</b> 2008/09/23
84               </li>
85               <li><b>Copyright:</b> 2007-2008, RWTH Aachen University
86               </li>
87            </ul>
88         </div>
89         <p class="footer"><br>
90            Published with wg_publish; V1.0<br></p>
91      </div>
92      <!--
93##### SOURCE BEGIN #####
94%% COM_ReadI2C
95% Requests and reads sensor data via I2C from a correctly configured digital sensor.
96%%
97%% Syntax
98% |ReturnBytes = COM_ReadI2C(Port, RequestLen, DeviceAddress, RegisterAddress)|
99%%
100% |ReturnBytes = COM_ReadI2C(Port, RequestLen, DeviceAddress, RegisterAddress, handle)|
101%%
102%% Description
103% This function is used to retrieve data from digital sensors (like the
104% ultrasonic) in a comfortable way. It is designed as a helping function
105% for developers wanting to access new sensors. For already implemented
106% sensors (e.g. ultrasound, as well as HiTechnic's acceleration and
107% infrared sensors), use the provided high-level functions such as
108% |GetUltrasonic|, |GetInfrared|, etc.
109%%
110% For I2C communication, usually the |NXT_SetInputMode| command has to
111% be used with the |LOWSPEED_9V| or |LOWSPEED| setting. Afterwards,
112% commands can be send with |NXT_LSWrite|. Once a sensor is correctly
113% working, i.e. has data available, you can use this function to
114% retrieve them.
115%%
116% In |COM_ReadI2C(Port, RequestLen, DeviceAddress, RegisterAddress)|,
117% |Port| is the sensor-port the sensor is connected to. |RequestLen|
118% specifies the amount of bytes you want to retrieve. For ultasound,
119% this is 1. |DeviceAddress| is the sensor's address on the I2C bus.
120% This sometimes can be changed, but not for the ultrasonic sensor.
121% Default value is 0x02 (2 in decimal). Finally, |RegisterAddress| is
122% the address where you want to read data from. For the ultrasound and
123% many other sensors, the "data section" starts at 0x42 (66 in decimal).
124%%
125% As last argument you can pass a valid NXT-handle to be used by this
126% function. If no handle is passed, the default set by
127% |COM_SetDefaultNXT| will be used.
128%%
129%%
130% *Returns:* |ReturnBytes|, byte-array (column vector) of uint8.
131% This array contains the raw sensor-data you requested. How to
132% interpret them depends on the sensor. If communication failed (even
133% after automatic retransmission) REPLACE_WITH_DASH_DASH e.g. when the sensor get's
134% disconnected while in use REPLACE_WITH_DASH_DASH an empty vector |[]| will be returned.
135%%
136%%
137% *Note:*
138%%
139%%
140% Please note that the return values of this function are of type uint8.
141% You have to convert them to double (using |double()|) before
142% performing calculations with them, otherwise you might get unexpected
143% results!
144%%
145% The sensor you are addressing with this command has to be correctly
146% opened and initialized of course REPLACE_WITH_DASH_DASH otherwise no valid data can be
147% received.
148%%
149%% Example
150% This example opens and reads the ultrasonic sensor
151   port = SENSOR_1;
152   handle = COM_OpenNXT('bluetooth.ini', 'check');
153
154   OpenUltrasonic(port);
155
156   % retrieve 1 byte from device 0x02, register 0x42
157   data = COM_ReadI2C(port, 1, uint8(2), uint8(66));
158
159   if isempty(data)
160       DistanceCM = -1;
161   else
162       % don'f forget this double()!!!
163       DistanceCM = double(data(1));
164   end%if
165%%
166%%
167%% See also
168% NXT_LSWrite, NXT_LSRead, NXT_LSGetStatus, NXT_SetInputMode, OpenUltrasonic,
169% GetUltrasonic, SENSOR_1, SENSOR_2, SENSOR_3, SENSOR_4
170%%
171%%
172%% Signature
173%%
174% * *Author:* Linus Atorf (see AUTHORS)
175% * *Date:* 2008/09/23
176% * *Copyright:* 2007-2008, RWTH Aachen University
177%
178
179##### SOURCE END #####
180-->
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