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<p>Hi - thanks for the responses!</p>
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<p>It is a very simple application that is only processing a 1 kHz timer for the purposes of this test. There is no other CPU load on the system. The only thing I do right now when the timer fires is calculate the time difference since the last timer fired.
Once a second, I output the average, min and max for that second.</p>
<p><br>
</p>
<p><span style="font-family: Calibri, Arial, Helvetica, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", NotoColorEmoji, "Segoe UI Symbol", "Android Emoji", EmojiSymbols; font-size: 16px;">I do have a delay it the main task, since it is just sitting there
idle. Would that account for such an increase in the time between the timer firing?</span><br>
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<p>I will try the POSIX API next.</p>
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<p>Thank you,</p>
<p>Janet</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Joel Sherrill <joel@rtems.org><br>
<b>Sent:</b> Wednesday, December 7, 2016 1:15:23 PM<br>
<b>To:</b> Janet Schneider<br>
<b>Cc:</b> users@rtems.org<br>
<b>Subject:</b> Re: 1kHz timer behavior on Cyclone V</font>
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<div class="gmail_quote">On Wed, Dec 7, 2016 at 11:44 AM, Janet Schneider <span dir="ltr">
<<a href="mailto:janetsc@fb.com" target="_blank">janetsc@fb.com</a>></span> wrote:<br>
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<p>Hello,</p>
<p><br>
</p>
<p>I am running a 1kHz timer test on the Altera Cyclone V dev board. I am trying to measure the average time period between the timer firing, and any variance on that latency.</p>
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</p>
<p>I'm seeing an average of 1003 microseconds between the timer firing. About once a second, I see the maximum time between the timer firing go up to 2500-3000 microseconds.</p>
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<div>There are two sets of timers. One is per clock tick and one is per second.</div>
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<div>My guesses are:</div>
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<div>Do you have a sleep/delay statement in your thread?</div>
<div>There may be some work updating the time that occurs once per second. The implementation of this area has changed so I don't remember offhand if this is still the case.</div>
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<p></p>
<p>I'm using rtems_clock_get_uptime_<wbr>nanoseconds() to measure the time that the timer fires. I have CONFIGURE_MICROSECONDS_PER_<wbr>TICK set to 500.</p>
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<div>What happens when the HW interrupt timer fires?</div>
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<div>--joel</div>
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<p>Has anyone else seen this (or something similar)? Any ideas what might be happening here?</p>
<p><br>
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<p>Thanks,</p>
<p>Janet</p>
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<br>
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