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<concept id="GUID-078E6232-31FA-5582-84B8-F5E3E4B14A05" xml:lang="en"><title>How

to start a heartbeat timer</title><shortdesc>Provides code snippet to show you how to start a heartbeat timer.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>A heartbeat timer, <codeph>CHeartbeat</codeph>, invokes a function at regular

intervals. You must define a class that implements the <codeph>MBeating</codeph> interface

to define:</p>

<ul>

<li id="GUID-5B54CE88-DE53-5635-BBF4-639B693C5BEC"><p>a function <codeph>Beat()</codeph> that

is called if the heartbeat timer is in synchronisation with the system clock</p> </li>

<li id="GUID-E20AD2FD-B847-52B6-8D1E-F01B2A971ABA"><p>a function <codeph>Synchronize()</codeph> that

is called if the heartbeat timer has got out of synchronisation with the system

clock</p> </li>

</ul>

<p>First, we define a class <codeph>CHeartbeatRunner</codeph> class that derives

from <codeph>MBeating</codeph>. </p>

<codeblock id="GUID-6D0B8C93-7F24-5002-A8FF-5C9F4C41EE7B" xml:space="preserve">class CHeartbeatRunner: public MBeating

    {

public:

    // Implement MBeating

    void Beat();

    void Synchronize();

    // Start timer

    void StartTimer();

private:

    CHeartbeat* iHeartbeat;

};</codeblock>

<p>Then, we can start the heartbeat timer. We pass the time interval for the

beats (allowable intervals are defined in 1/12s of a second by <codeph>TTimerLockSpec</codeph>),

and the object implementing <codeph>MBeating</codeph>.</p>

<codeblock id="GUID-C0BD2194-9FED-5C2B-B900-A028210CF78C" xml:space="preserve">void CHeartbeatRunner::StartTimer()

    {

    iHeartbeat=CHeartbeat::NewL(0); // neutral priority

    iHeartbeat->Start(ETwelveOClock,this); // 1 second intervals

    }</codeblock>