88 lines
1.8 KiB
C
88 lines
1.8 KiB
C
#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.h>
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#include <time.h>
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#include <sched.h>
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#include <sys/mman.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdbool.h>
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#include <stdint.h>
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#define GPIO_EXPORT "/sys/class/gpio/export"
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#define GPIO_UNEXPORT "/sys/class/gpio/unexport"
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#define GPIO_GPIOG11 "/sys/class/gpio/gpio203"
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#define GPIOG11 "203"
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static int open_gpio()
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{
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// unexport pin out of sysfs (reinitialization)
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int f = open (GPIO_UNEXPORT, O_WRONLY);
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write (f, GPIOG11, strlen(GPIOG11));
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close (f);
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// export pin to sysfs
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f = open (GPIO_EXPORT, O_WRONLY);
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write (f, GPIOG11, strlen(GPIOG11));
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close (f);
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// config pin
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f = open (GPIO_GPIOG11 "/direction", O_WRONLY);
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write (f, "out", 3);
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close (f);
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// open gpio value attribute
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f = open (GPIO_GPIOG11 "/value", O_RDWR);
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return f;
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}
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/**
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* main program...
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*/
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int main()
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{
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cpu_set_t my_set;
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CPU_ZERO(&my_set);
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CPU_SET(2, &my_set);
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sched_setaffinity(0, sizeof(cpu_set_t), &my_set);
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int gpio = open_gpio();
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bool on = false;
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struct timespec start_time;
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struct timespec stop_time;
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clock_gettime (CLOCK_MONOTONIC, &start_time); // setup...
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// --> measurement with internal timers
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clock_gettime (CLOCK_MONOTONIC, &start_time);
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for (int i=0; i<1000; i++) {
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if (on) {
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pwrite (gpio, "1", sizeof("1"), 0);
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} else {
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pwrite (gpio, "0", sizeof("0"), 0);
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}
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on = !on;
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}
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clock_gettime (CLOCK_MONOTONIC, &stop_time);
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long long t = (stop_time.tv_nsec - start_time.tv_nsec) +
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(stop_time.tv_sec - start_time.tv_sec) * 1000000000;
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printf ("pwrite (gpio, \"1\", sizeof(\"1\"), 0) -> %lld ns\n", t/1000);
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// --> measurement with oscilloscope
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while(true) {
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if (on) {
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pwrite (gpio, "1", sizeof("1"), 0);
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} else {
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pwrite (gpio, "0", sizeof("0"), 0);
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}
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on = !on;
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}
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return 0;
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}
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