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<div id="projectname">UNICENS <span id="projectnumber">V2.1.0-3491</span></div>
<div id="projectbrief">User Manual and API Reference</div>
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<div class="title">Node Discovery </div> </div>
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<div class="textblock"><h1>Introduction</h1>
<p>The idea behind the Node Discovery service is that nodes are allowed to use the bus only if they meet certain requirements. A central instance detects all nodes and checks if they fit to the intended system. Nodes passing the check get an explicit "invitation" to join the system.</p>
<h1>Initialization</h1>
<p>The application provides the two callback functions of the Node Discovery service.</p>
<div class="fragment"><div class="line"><a class="code" href="struct_ucs___init_data__t.html" title="UNICENS initialization structure used by function Ucs_Init().">Ucs_InitData_t</a> init_data;</div>
<div class="line"></div>
<div class="line"><span class="comment">/* Node Discovery Section */</span> </div>
<div class="line">init_data.<a class="code" href="struct_ucs___init_data__t_a97b13c03602cc54884ae1765c518bd7b.html#a97b13c03602cc54884ae1765c518bd7b" title="The initialization data of the Node Discovery.">nd</a>.<a class="code" href="struct_ucs___nd___init_data__t_a98b9ccad2c6c5fa2edaf472151ee853c.html#a98b9ccad2c6c5fa2edaf472151ee853c" title="Callback function reporting the results of the Node Discovery service.">report_fptr</a> = &App_OnNodeDiscoveryResult;</div>
<div class="line">init_data.<a class="code" href="struct_ucs___init_data__t_a97b13c03602cc54884ae1765c518bd7b.html#a97b13c03602cc54884ae1765c518bd7b" title="The initialization data of the Node Discovery.">nd</a>.<a class="code" href="struct_ucs___nd___init_data__t_ab9bc02a84c7daeff234344541d41be62.html#ab9bc02a84c7daeff234344541d41be62" title="Callback function asking for evaluation of the found signature.">eval_fptr</a> = &App_OnNodeDiscoveryEval;</div>
</div><!-- fragment --><table class="mns_ic_table">
<tr>
<td id="mns_ic_started"> </td><td>See also <em>Getting Started</em>, section <a class="el" href="_p__u_m__s_t_a_r_t_e_d__i_n_i_t.html">Initialization</a>. </td></tr>
</table>
<dl class="section note"><dt>Note</dt><dd>The function names App_OnNodeDiscoveryResult() and App_OnNodeDiscoveryEval() are just example names. Nevertheless they will be used in the description below to designate the respective functions.</dd></dl>
<h1>Operation</h1>
<p>The application maintains at least two lists:</p>
<dl>
<dt><em>set_list</em> </dt>
<dd><p class="startdd">Contains the signatures of the nodes the system shall contain.</p>
<p class="enddd"></p>
</dd>
<dt><em>device_list</em> </dt>
<dd>Contains the signatures of the nodes detected in the system. </dd>
</dl>
<p>For debuggting purposes it may be useful to have a third list:</p>
<dl>
<dt><em>unknown_list</em> </dt>
<dd><p class="startdd">Signatures of the nodes which are detected but are not part of the <em>set_list</em>.</p>
<p class="enddd"></p>
</dd>
</dl>
<p>After startup all nodes are initialized and not part of the system. The application starts the Node Discovery service by calling <a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y_ga50a5b00d5bbd1ad324478509dc524eec.html#ga50a5b00d5bbd1ad324478509dc524eec" title="Starts the Node Discovery service.">Ucs_Nd_Start()</a>. It asks every node for its signature (<a class="el" href="struct_ucs___signature__t.html" title="This structure holds the signature of the Hello, Welcome and Signature messages. It supports the sign...">Ucs_Signature_t</a>). Each detected node will be presented to the application via the callback function App_OnNodeDiscoveryEval(). In this function the application decides how the Node Discovery service shall proceed with the node.</p>
<p>The evaluation has to follow these rules:</p>
<ul>
<li>If the node is not part of the <em>set_list</em>, it is regarded as unknown (<a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y___t_y_p_e_s_gae1f89dbd75e3d76917273450df37ff66.html#ggae1f89dbd75e3d76917273450df37ff66a4ed7307250366668604925bf3650be4c">UCS_ND_CHK_UNKNOWN</a>) and will be ignored.</li>
<li>If the node is part of the <em>set_list</em> and is not yet in the <em>device_list</em>, the Node Discovery Service shall try to add the node to network (<a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y___t_y_p_e_s_gae1f89dbd75e3d76917273450df37ff66.html#ggae1f89dbd75e3d76917273450df37ff66a0c15fbb8aa9ee8dbf0362b9e9a8b6942">UCS_ND_CHK_WELCOME</a>).</li>
<li>If the node is already part of the <em>device_list</em>, there are two possibilities: the node in the <em>device_list</em> experienced a reset or there are two nodes with the same signature. Evaluation result is <a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y___t_y_p_e_s_gae1f89dbd75e3d76917273450df37ff66.html#ggae1f89dbd75e3d76917273450df37ff66acdbc82cdd701e67cdd7520172767ba75">UCS_ND_CHK_UNIQUE</a>. The Node Discovery service will perform further tests.</li>
</ul>
<p>The result of the evaluation is passed as the return value of App_OnNodeDiscoveryEval() (for possible values see <a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y___t_y_p_e_s_gae1f89dbd75e3d76917273450df37ff66.html#gae1f89dbd75e3d76917273450df37ff66">Ucs_Nd_CheckResult_t</a>).</p>
<p>When the Node Discovery process for a certain node is finished, the callback function App_OnNodeDiscoveryResult() is called. Its parameter <b>code</b> informs the application about the result of the node (for possible values see <a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y___t_y_p_e_s_ga6736f9abd905dafe99d1337ac672f94e.html#ga6736f9abd905dafe99d1337ac672f94e">Ucs_Nd_ResCode_t</a>).</p>
<p>The Node Discovery service asks periodically for new nodes. So it will detect nodes which start up slowly and nodes which experienced a reset.</p>
<p>App_OnNodeDiscoveryResult() informs also about general events like NetOff, unexpected error and stop of the Node Discovery service by application command. In these cases the parameter <b>signature</b> will be NULL.</p>
<p>If a Netoff event happens, the Node Discovery service stops. It restarts automatically if it detects a NetOn event.</p>
<p>The application can stop the Node Discovery service via <a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y_ga637e441520f7b203e551274f17febfb6.html#ga637e441520f7b203e551274f17febfb6" title="Stops the Node Discovery service.">Ucs_Nd_Stop()</a>.</p>
<p>It is possible to reset all nodes to the initial state they had after startup by calling <a class="el" href="group___g___u_c_s___n_o_d_e___d_i_s_c_o_v_e_r_y_gabab6c431e235fe0211f5f1525f9cff2e.html#gabab6c431e235fe0211f5f1525f9cff2e" title="Initializes all nodes.">Ucs_Nd_InitAll()</a>. </p>
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