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/*
Copyright (c) 2016 CurlyMo <curlymoo1@gmail.com>
This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <time.h>
#include "wiringx.h"
void drop_privileges();
int main() {
if(wiringXSetup("raspberrypi3", NULL) == -1) {
wiringXGC();
return -1;
}
pinMode(9, PINMODE_OUTPUT);
digitalWrite(9, HIGH);
pinMode(9, PINMODE_INPUT);
pinMode(8, PINMODE_OUTPUT);
drop_privileges();
// start bit
digitalWrite(8, HIGH);
usleep(18000);
digitalWrite(8, LOW);
int bit = -3;
char data[5];
memset(&data[0], 0, 5);
int trials = 3;
while ((bit != 40) || ((data[0]+data[1]+data[2]+data[3]-data[4]) % 255 != 0) || ((data[0]|data[1]|data[2]|data[3]|data[4]) == 0)) {
trials--;
if (trials <= 0) {
fprintf(stderr, "Failed to obtain valid reading within 3 trials.\n");
return -1;
}
sleep(2);
if (bit > -3)
fprintf(stderr, ".");
// start bit
digitalWrite(8, HIGH);
usleep(18000);
digitalWrite(8, LOW);
long int cycles = 0;
int last_state = digitalRead(9);
// ignore 2 bits: reaction on command + "official" start bit
bit = -2;
memset(&data[0], 0, 5);
while (cycles < 100000) {
cycles++;
if (last_state == digitalRead(9))
continue;
if (last_state == 1) {
if ((bit >= 0) && (cycles>200))
data[bit / 8] |= 1 << 7 - (bit % 8);
bit++;
}
cycles = 0;
last_state = 1-last_state;
}
}
FILE *of;
of = fopen("/srv/http/tmp/sensor", "w");
if (of == NULL) {
fprintf(stderr, "Failed to open '%s' for writing.\n", "/srv/http/tmp/sensor");
return -1;
}
time_t now = time(NULL);
char time_str[20];
strftime(time_str, 20, "%Y-%m-%d %H:%M:%S", gmtime(&now));
fprintf(of, "RH: %f %%\n", data[0] + data[1]/256.);
fprintf(of, "T: %f °C\n", data[2] + data[3]/256.);
fprintf(of, "t: %s\n", time_str);
fclose(of);
} // main
//
// Drop (root) privileges
//
void drop_privileges() {
/* Drop superuser privileges in correct order */
int is_already_unprivileged = 0;
if (setgid(65534) == -1) { // nobody
perror("can't drop group privileges");
if (! (is_already_unprivileged = (errno == 1)))
exit(-1);
}
if (setuid(65534) == -1) { // nobody
perror("can't drop user privileges");
if (is_already_unprivileged != (errno == 1))
exit(-1);
}
} // drop_privileges
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