wiringPi_Blueberry/examples/delayTest.c

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2023-08-11 15:53:17 +08:00
/*
* delayTest.c:
* Just a little test program I'm using to experiment with
* various timings and latency, etc.
*
* Copyright (c) 2012-2013 Gordon Henderson. <projects@drogon.net>
***********************************************************************
* This file is part of wiringPi:
* https://projects.drogon.net/raspberry-pi/wiringpi/
*
* wiringPi is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* wiringPi is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with wiringPi. If not, see <http://www.gnu.org/licenses/>.
***********************************************************************
*/
#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>
#define CYCLES 1000
int main()
{
int x ;
struct timeval t1, t2, t3 ;
int t ;
int max, min ;
int del ;
int underRuns, overRuns, exactRuns, bogusRuns, total ;
int descheds ;
// Baseline test
gettimeofday (&t1, NULL) ;
gettimeofday (&t2, NULL) ;
t = t2.tv_usec - t1.tv_usec ;
printf ("Baseline test: %d\n", t);
for (del = 1 ; del < 200 ; ++del)
{
underRuns = overRuns = exactRuns = total = 0 ;
descheds = 0 ;
max = 0 ;
min = 999 ;
for (x = 0 ; x < CYCLES ; ++x)
{
for (;;) // Repeat this if we get a delay over 999uS
{ // -> High probability Linux has deschedulled us
gettimeofday (&t1, NULL) ;
usleep (del) ;
// delayMicroseconds (del) ;
gettimeofday (&t2, NULL) ;
timersub (&t2, &t1, &t3) ;
t = t3.tv_usec ;
if (t > 999)
{
++descheds ;
continue ;
}
else
break ;
}
if (t == del)
++exactRuns ;
else if (t < del)
++underRuns ;
else if (t > del)
++overRuns ;
if (t > max)
max = t ;
else if (t < min)
min = t ;
total += t ;
}
printf ("Delay: %3d. Min: %3d, Max: %3d, Unders: %3d, Overs: %3d, Exacts: %3d, Average: %3d, Descheds: %2d\n",
del, min, max, underRuns, overRuns, exactRuns, total / CYCLES, descheds) ;
fflush (stdout) ;
usleep (1000) ;
}
return 0 ;
}