108 lines
2.6 KiB
C
108 lines
2.6 KiB
C
/*
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* delayTest.c:
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* Just a little test program I'm using to experiment with
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* various timings and latency, etc.
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*
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* Copyright (c) 2012-2013 Gordon Henderson. <projects@drogon.net>
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***********************************************************************
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* This file is part of wiringPi:
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* https://projects.drogon.net/raspberry-pi/wiringpi/
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*
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* wiringPi is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* wiringPi is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with wiringPi. If not, see <http://www.gnu.org/licenses/>.
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***********************************************************************
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <wiringPi.h>
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#include <sys/time.h>
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#define CYCLES 1000
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int main()
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{
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int x ;
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struct timeval t1, t2 ;
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int t ;
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int max, min ;
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int del ;
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int underRuns, overRuns, exactRuns, total ;
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int descheds ;
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if (wiringPiSetup () == -1)
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return 1 ;
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piHiPri (10) ; sleep (1) ;
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// Baseline test
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gettimeofday (&t1, NULL) ;
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gettimeofday (&t2, NULL) ;
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t = t2.tv_usec - t1.tv_usec ;
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printf ("Baseline test: %d\n", t);
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for (del = 1 ; del < 200 ; ++del)
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{
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underRuns = overRuns = exactRuns = total = 0 ;
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descheds = 0 ;
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max = del ;
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min = del ;
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for (x = 0 ; x < CYCLES ; ++x)
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{
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for (;;) // Repeat this if we get a delay over 999uS
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{ // -> High probability Linux has deschedulled us
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gettimeofday (&t1, NULL) ;
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delayMicroseconds (del) ;
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gettimeofday (&t2, NULL) ;
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if (t2.tv_usec < t1.tv_usec) // Counter wrapped
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t = (1000000 + t2.tv_usec) - t1.tv_usec;
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else
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t = t2.tv_usec - t1.tv_usec ;
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if (t > 999)
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{
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++descheds ;
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continue ;
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}
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else
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break ;
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}
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if (t > max)
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{
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max = t ;
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++overRuns ;
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}
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else if (t < min)
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{
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min = t ;
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++underRuns ;
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}
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else
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++exactRuns ;
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total += t ;
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}
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printf ("Delay: %3d. Min: %3d, Max: %3d, Unders: %3d, Overs: %3d, Exacts: %3d, Average: %3d, Descheds: %2d\n",
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del, min, max, underRuns, overRuns, exactRuns, total / CYCLES, descheds) ;
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fflush (stdout) ;
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delay (1) ;
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}
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return 0 ;
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}
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