104 lines
2.1 KiB
C
104 lines
2.1 KiB
C
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <sys/time.h>
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#include <poll.h>
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#include "rpi.h"
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#define GPIO 26
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static int write_file(const char *filename, const char *string) {
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int fd = open(filename, O_WRONLY);
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if (fd == -1)
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return fd;
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write(fd, string, strlen(string));
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close(fd);
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return 0;
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}
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static int export_gpio(int gpio) {
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char filename[512];
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char string[128];
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snprintf(filename, sizeof(filename)-1, "/sys/class/gpio/export");
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snprintf(string, sizeof(string)-1, "%d", gpio);
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if (write_file(filename, string))
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return -1;
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snprintf(filename, sizeof(filename)-1, "/sys/class/gpio/gpio%d/direction", gpio);
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snprintf(string, sizeof(string)-1, "in");
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if (write_file(filename, string))
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return -1;
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snprintf(filename, sizeof(filename)-1, "/sys/class/gpio/gpio%d/edge", gpio);
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snprintf(string, sizeof(string)-1, "falling");
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if (write_file(filename, string))
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return -1;
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return 0;
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}
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int main(int argc, char *argv[])
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{
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char str[256];
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struct pollfd pfd;
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int fd, gpio;
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char buf[8];
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if (argc > 1)
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gpio = atoi(argv[1]);
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else
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gpio = GPIO;
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if (gpioInitialise()) {
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fprintf(stderr, "Unable to initialize GPIO! Are you running as root?\n");
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return 0;
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}
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gpioSetPullUpDown(gpio, PI_PUD_UP);
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if (export_gpio(gpio)) {
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perror("Unable to export GPIO");
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return 1;
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}
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snprintf(str, sizeof(str)-1, "/sys/class/gpio/gpio%d/value", gpio);
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if ((fd = open(str, O_RDONLY)) < 0)
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{
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fprintf(stderr, "Failed, gpio %d not exported.\n", gpio);
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exit(1);
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}
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pfd.fd = fd;
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pfd.events = POLLPRI;
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lseek(fd, 0, SEEK_SET); /* consume any prior interrupt */
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read(fd, buf, sizeof buf);
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while (1) {
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poll(&pfd, 1, -1); /* wait for interrupt */
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lseek(fd, 0, SEEK_SET); /* consume interrupt */
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read(fd, buf, sizeof buf);
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//fprintf(stderr, "Delay...");
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usleep(1000);
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/* Read value after brief debounce */
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lseek(fd, 0, SEEK_SET);
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//fprintf(stderr, "Re-read...");
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read(fd, buf, sizeof buf);
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if (buf[0] != '0')
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continue;
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printf("START\n");
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fflush(stdout);
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usleep(1000);
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}
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exit(0);
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}
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