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#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <error.h>
#include <errno.h>
#include <limits.h>
#include <unistd.h>
#include <string.h>
#include "linux/input.h"
#define INPUT_DEV_NODE "/dev/input/by-path/platform-ffc04000.i2c-event"
#define SYSFS_DEVICE_DIR "/sys/devices/platform/soc/ffc04000.i2c/i2c-0/0-0053/"
#define EV_CODE_X (0)
#define EV_CODE_Y (1)
#define EV_CODE_Z (2)
#define LOOP_COUNT (100)
void write_sysfs_cntl_file(const char *dir_name, const char *file_name,
const char *write_str) {
char path[PATH_MAX];
int path_length;
int file_fd;
int result;
// create the path to the file we need to open
path_length = snprintf(path, PATH_MAX, "%s/%s", dir_name, file_name);
if(path_length < 0)
error(1, 0, "path output error");
if(path_length >= PATH_MAX)
error(1, 0, "path length overflow");
// open the file
file_fd = open(path, O_WRONLY | O_SYNC);
if(file_fd < 0)
error(1, errno, "could not open file '%s'", path);
// write the string to the file
result = write(file_fd, write_str, strlen(write_str));
if(result < 0)
error(1, errno, "writing to '%s'", path);
if((size_t)(result) != strlen(write_str))
error(1, errno, "buffer underflow writing '%s'", path);
// close the file
result = close(file_fd);
if(result < 0)
error(1, errno, "could not close file '%s'", path);
}
int main(void) {
int event_dev_fd;
const char *input_dev_node = INPUT_DEV_NODE;
int result;
struct input_event the_event;
// enable adxl
write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "disable", "0");
// set the sample rate to maximum
write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "rate", "15");
// do not auto sleep
write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "autosleep", "0");
// open the event device node
event_dev_fd = open(input_dev_node, O_RDONLY | O_SYNC);
if(event_dev_fd < 0)
error(1, errno, "could not open file '%s'", input_dev_node);
printf("Please tap the DE10 Nano board.\n");
while(1) {
// read the next event
result = read(event_dev_fd, &the_event,
sizeof(struct input_event));
if(result < 0)
error(1, errno, "reading %d from '%s'",
sizeof(struct input_event),
input_dev_node);
if(result != sizeof(struct input_event))
error(1, 0, "did not read %d bytes from '%s'",
sizeof(struct input_event),
input_dev_node);
if((the_event.type == EV_KEY) && (the_event.code == BTN_TOUCH))
break;
}
printf("Tap detected.\n");
// close the device node
result = close(event_dev_fd);
if(result < 0)
error(1, errno, "could not close file '%s'", input_dev_node);
// disable adxl
write_sysfs_cntl_file(SYSFS_DEVICE_DIR, "disable", "1");
}
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