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12      <title>NXT_SendKeepAlive</title>
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19<p class="header">RWTH - Mindstorms NXT Toolbox</p>
20      <div class="content">
21         <h1>NXT_SendKeepAlive</h1>
22         <!--introduction-->
23         <p>Sends a KeepAlive packet. Optional: requests sleep time limit.</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="#15">Examples</a></li>
31               <li><a href="#19">See also</a></li>
32               <li><a href="#21">Signature</a></li>
33            </ul>
34         </div>
35         <h2>Syntax<a name="2"></a></h2>
36         <p><tt>[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode)</tt></p>
37         <p><tt>[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode, handle)</tt></p>
38         <h2>Description<a name="5"></a></h2>
39         <p><tt>[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode)</tt> sends a KeepAlive packet to the NXT Brick to get the current sleep time limit of the Brick in milliseconds. By the <tt>ReplyMode</tt> one can request an acknowledgement for the packet transmission. The two strings <tt>'reply'</tt> and <tt>'dontreply'</tt> are valid. <tt>status</tt> indicates if an error occures by the packet transmission. Function <tt>checkStatusBytes</tt> is interpreting this information per default. The value <tt>SleepTimeLimit</tt> contains the time in milliseconds after the NXT brick will turn off automatically. The variable will only be set if <tt>ReplyMode</tt> is <tt>'reply'</tt>. The sleep time limit setting can only  be modified using the on-screen-menu on the brick itself.
40         </p>
41         <p>Using <tt>'dontreply'</tt> will just send a keep-alive packet. This means, the NXT internal counter when to shut down automatically (this is a setting
42            that can only be accessed directly on the NXT) will be reset. This counter is not an inactivity counter: Bluetooth traffic
43            will NOT stop the NXT from turning off. E.g. if the sleep limit is set to 10 minutes, the only way to keep the NXT Brick from
44            turning off is to send a keep-alive packet within this time.
45         </p>
46         <p>If you use replymode <tt>'reply'</tt>, SleepTimeLimit tells you the current setting on the brick, in milliseconds. 0 means sleep timer is disabled. -1 is an invalid
47            answer: You obviously didn't use <tt>'reply'</tt> and still tried to get an answer.
48         </p>
49         <p><tt>[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode, handle)</tt> uses the given NXT connection <tt>handle</tt>. This should be a struct containing a serial handle on a PC system and a file handle on a Linux system.
50         </p>
51         <p>If no NXT handle is specified the default one (<tt>COM_GetDefaultNXT</tt>) is used.
52         </p>
53         <p>For more details see the official LEGO Mindstorms communication protocol.</p>
54         <p><b>Note:</b></p>
55         <p>This function is also used if you call <tt>COM_OpenNXT()</tt> with the optional <tt>'check'</tt> parameter. Then a keep-alive packet is send and the answer will be received to check for a correctly working bidirectional
56            bluetooth connection.
57         </p>
58         <h2>Examples<a name="15"></a></h2><pre class="codeinput">   [status SleepTimeLimit] = NXT_SendKeepAlive(<span class="string">'reply'</span>);
59</pre><pre class="codeinput">   NXT_SendKeepAlive(<span class="string">'dontreply'</span>);
60</pre><pre class="codeinput">   handle = COM_OpenNXT(<span class="string">'bluetooth.ini'</span>,<span class="string">'check'</span>);
61   [status SleepTimeLimit] = NXT_SendKeepAlive(<span class="string">'reply'</span>, handle);
62</pre><h2>See also<a name="19"></a></h2>
63         <p><a href="COM_OpenNXT.html">COM_OpenNXT</a>, <a href="NXT_GetBatteryLevel.html">NXT_GetBatteryLevel</a></p>
64         <h2>Signature<a name="21"></a></h2>
65         <div>
66            <ul>
67               <li><b>Author:</b> Linus Atorf (see AUTHORS)
68               </li>
69               <li><b>Date:</b> 2007/10/15
70               </li>
71               <li><b>Copyright:</b> 2007-2008, RWTH Aachen University
72               </li>
73            </ul>
74         </div>
75         <p class="footer"><br>
76            Published with wg_publish; V1.0<br></p>
77      </div>
78      <!--
79##### SOURCE BEGIN #####
80%% NXT_SendKeepAlive
81% Sends a KeepAlive packet. Optional: requests sleep time limit.
82%%
83%% Syntax
84% |[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode)|
85%%
86% |[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode, handle)|
87%%
88%% Description
89% |[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode)| sends a KeepAlive packet to the NXT
90% Brick to get the current sleep time limit of the Brick in milliseconds. By the |ReplyMode|
91% one can request an acknowledgement for the packet transmission. The two strings |'reply'| and
92% |'dontreply'| are valid. |status| indicates if an error occures by the packet transmission.
93% Function |checkStatusBytes| is interpreting this information per default. The value
94% |SleepTimeLimit| contains the time in milliseconds after the NXT brick will turn off
95% automatically. The variable will only be set if |ReplyMode| is |'reply'|. The sleep time limit
96% setting can only  be modified using the on-screen-menu on the brick itself.
97%%
98% Using |'dontreply'| will just send a keep-alive packet. This means, the NXT internal counter when
99% to shut down automatically (this is a setting that can only be accessed directly on the NXT)
100% will be reset. This counter is not an inactivity counter: Bluetooth traffic will NOT stop the
101% NXT from turning off. E.g. if the sleep limit is set to 10 minutes, the only way to keep the NXT
102% Brick from turning off is to send a keep-alive packet within this time.
103%%
104% If you use replymode |'reply'|, SleepTimeLimit tells you the current setting on the brick, in
105% milliseconds. 0 means sleep timer is disabled. -1 is an invalid answer: You obviously didn't use
106% |'reply'| and still tried to get an answer.
107%%
108% |[status SleepTimeLimit] = NXT_SendKeepAlive(ReplyMode, handle)| uses the given NXT
109% connection |handle|. This should be a struct containing a serial handle on a PC system and a file handle on a Linux
110% system.
111%%
112% If no NXT handle is specified the default one (|COM_GetDefaultNXT|) is used.
113%%
114% For more details see the official LEGO Mindstorms communication protocol.
115%%
116%%
117% *Note:*
118%%
119% This function is also used if you call |COM_OpenNXT()| with the optional |'check'| parameter. Then
120% a keep-alive packet is send and the answer will be received to check for a correctly working
121% bidirectional bluetooth connection.
122%%
123%% Examples
124   [status SleepTimeLimit] = NXT_SendKeepAlive('reply');
125%%
126   NXT_SendKeepAlive('dontreply');
127%%
128   handle = COM_OpenNXT('bluetooth.ini','check');
129   [status SleepTimeLimit] = NXT_SendKeepAlive('reply', handle);
130%%
131%% See also
132% COM_OpenNXT, NXT_GetBatteryLevel
133%%
134%% Signature
135%%
136% * *Author:* Linus Atorf (see AUTHORS)
137% * *Date:* 2007/10/15
138% * *Copyright:* 2007-2008, RWTH Aachen University
139%
140
141##### SOURCE END #####
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