Read S0 impulses from mouse events

s0event.c

#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>
#include <linux/input.h>
#include <stdint.h>

// config /////////////////////////

#define IMPULSES_PER_KWH 800

char * button_id[] = { "L", "R", "M" };

//////////////////////////////////

double tv_diff(struct timeval * tv1, struct timeval * tv2) {
	if (tv1->tv_usec < tv2->tv_usec)
		return (tv2->tv_sec - tv1->tv_sec) + (tv2->tv_usec - tv1->tv_usec)/1e6;
	else
		return (tv2->tv_sec - tv1->tv_sec - 1) + (tv1->tv_usec - tv2->tv_usec)/1e6;
}

#define test_bit(p, n) !!(p[n>>3] & (1u << (n&7)))

int isButtonPressed(int fd, unsigned short code) {
	uint8_t keys[(KEY_MAX<<3)+1];
	memset(keys, 0, sizeof(keys));
	ioctl(fd, EVIOCGKEY(sizeof(keys)), keys);
	return test_bit(keys, code);
}

int main(int argc, char* argv[])
{
	char * dev;
	int fd;
	ssize_t rc;
	struct input_event ev;
	struct timeval prev[3];

	if (argc < 2) {
		fprintf(stderr, "Usage: %s /dev/input/eventX\n", argv[0]);
		return 1;
	}
	dev = argv[1];

	memset(prev, 0, sizeof(prev));

	printf("using %s\n", dev);
	if ((fd = open(dev, O_RDWR)) < 0) {
		perror("open event device");
		return 1;
	}

	while ((rc = read(fd, &ev, sizeof(ev))) > 0) {
		char timestr[32];
//		printf("event: type %04hx code %04hx value %08x\n", ev.type, ev.code, ev.value);
		if (ev.type == EV_KEY && (ev.code >= BTN_LEFT && ev.code <= BTN_MIDDLE) && ev.value) {
			int button = ev.code - BTN_LEFT;
			if (ev.code == BTN_RIGHT)
				printf("Tarif: %s\n", isButtonPressed(fd, BTN_MIDDLE) ? "NT" : "HT");

			strftime(timestr, sizeof(timestr), "%Y-%m-%d %H:%M:%S", localtime(&ev.time.tv_sec) );
			printf("%s.%06ld  button %s (%d): ", timestr, ev.time.tv_usec, button_id[button], button);

			if (prev[button].tv_sec) {
				double tdiff = tv_diff(&prev[button], &ev.time);
				double p = (3600.0 / IMPULSES_PER_KWH * 1000) / tdiff;
				printf("t_diff = %0.3f s   P = %0.3f W\n", tdiff, p);
			} else {
				printf("first impulse\n");
			}
			memcpy(&prev[button], &ev.time, sizeof(prev[button]));
		}
	}
}