Mercurial > mbsePi-apps / file comparison
comparison: dht11/dht11.c
dht11/dht11.c
- changeset 538
- 6d139c21e22c
- parent 537
- 4eebab50993e
- child 539
- 300b5c4cd977
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| 1 /***************************************************************************** | |
| 2 * Copyright (C) 2014 | |
| 3 * | |
| 4 * Michiel Broek <mbroek at mbse dot eu> | |
| 5 * | |
| 6 * This file is part of the mbsePi-apps | |
| 7 * | |
| 8 * This is free software; you can redistribute it and/or modify it | |
| 9 * under the terms of the GNU General Public License as published by the | |
| 10 * Free Software Foundation; either version 2, or (at your option) any | |
| 11 * later version. | |
| 12 * | |
| 13 * mbsePi-apps is distributed in the hope that it will be useful, but | |
| 14 * WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 16 * General Public License for more details. | |
| 17 * | |
| 18 * You should have received a copy of the GNU General Public License | |
| 19 * along with EC-65K; see the file COPYING. If not, write to the Free | |
| 20 * Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. | |
| 21 *****************************************************************************/ | |
| 22 | |
| 23 #include "../config.h" | |
| 24 #include <stdio.h> | |
| 25 #include <stdlib.h> | |
| 26 #include <stdint.h> | |
| 27 #include <stdarg.h> | |
| 28 #include <syslog.h> | |
| 29 #include <unistd.h> | |
| 30 | |
| 31 #include "dht11.h" | |
| 32 | |
| 33 #ifdef HAVE_WIRINGPI_H | |
| 34 #include <wiringPi.h> | |
| 35 | |
| 36 #define MAXTIMINGS 100 | |
| 37 | |
| 38 int dht11_pin = -1; | |
| 39 int dht11_temperature = -1; | |
| 40 int dht11_humidity = -1; | |
| 41 int dht11_valid = FALSE; | |
| 42 int dht11_t_offset = 0; | |
| 43 int dht11_h_offset = 0; | |
| 44 | |
| 45 | |
| 46 | |
| 47 static uint8_t sizecvt(const int read_value) { | |
| 48 /* | |
| 49 * digitalRead() and friends from wiringpi are defined as returning a value | |
| 50 * < 256. However, they are returned as int() types. This is a safety function | |
| 51 */ | |
| 52 if (read_value > 255 || read_value < 0) { | |
| 53 syslog(LOG_NOTICE, "invalid data from wiringPi library"); | |
| 54 } | |
| 55 | |
| 56 return (uint8_t)read_value; | |
| 57 } | |
| 58 | |
| 59 | |
| 60 | |
| 61 /* | |
| 62 * DHT11 sensor read. This should be used in a thread loop. | |
| 63 */ | |
| 64 void dht11Read(void) { | |
| 65 int tries = 5; | |
| 66 unsigned short got_correct_data = 0; | |
| 67 | |
| 68 if (dht11_pin == -1) | |
| 69 return; | |
| 70 | |
| 71 while (tries && !got_correct_data) { | |
| 72 uint8_t laststate = HIGH; | |
| 73 uint8_t counter = 0; | |
| 74 uint8_t j = 0, i = 0; | |
| 75 int dht11_dat[5] = {0,0,0,0,0}; | |
| 76 | |
| 77 /* | |
| 78 * Select output mode to send the start signal. | |
| 79 */ | |
| 80 pinMode(dht11_pin, OUTPUT); | |
| 81 digitalWrite(dht11_pin, HIGH); | |
| 82 usleep(1000); | |
| 83 | |
| 84 /* | |
| 85 * Low for at least 18 milliseconds | |
| 86 */ | |
| 87 digitalWrite(dht11_pin, LOW); | |
| 88 usleep(20000); | |
| 89 digitalWrite(dht11_pin, HIGH); | |
| 90 pinMode(dht11_pin, INPUT); | |
| 91 | |
| 92 /* | |
| 93 * Detect change and read data | |
| 94 */ | |
| 95 for (i=0; i<MAXTIMINGS; i++) { | |
| 96 counter = 0; | |
| 97 delayMicroseconds(10); | |
| 98 while (sizecvt(digitalRead(dht11_pin)) == laststate) { | |
| 99 counter++; | |
| 100 delayMicroseconds(1); | |
| 101 if (counter == 255) { | |
| 102 break; | |
| 103 } | |
| 104 } | |
| 105 laststate = sizecvt(digitalRead(dht11_pin)); | |
| 106 | |
| 107 if (counter == 255) | |
| 108 break; | |
| 109 | |
| 110 /* | |
| 111 * ignore first 3 transitions | |
| 112 */ | |
| 113 if ((i >= 4) && (i%2 == 0)) { | |
| 114 | |
| 115 // shove each bit into the storage bytes | |
| 116 dht11_dat[(int)((double)j/8)] <<= 1; | |
| 117 if (counter > 16) | |
| 118 dht11_dat[(int)((double)j/8)] |= 1; | |
| 119 j++; | |
| 120 } | |
| 121 } | |
| 122 | |
| 123 /* | |
| 124 * If there is no sensor, j = 0 | |
| 125 */ | |
| 126 if ((counter == 255) && (j == 0)) { | |
| 127 if (dht11_temperature != -1) { | |
| 128 syslog(LOG_NOTICE, "dht11 sensor disappeared"); | |
| 129 } else { | |
| 130 syslog(LOG_NOTICE, "dht11 sensor not present"); | |
| 131 } | |
| 132 dht11_temperature = -1; | |
| 133 dht11_humidity = -1; | |
| 134 dht11_valid = FALSE; | |
| 135 return; | |
| 136 } | |
| 137 | |
| 138 /* | |
| 139 * check we read 40 bits (8bit x 5 ) + verify checksum in the last byte | |
| 140 * print it out if data is good | |
| 141 */ | |
| 142 if ((j >= 40) && (dht11_dat[4] == ((dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF))) { | |
| 143 got_correct_data = 1; | |
| 144 | |
| 145 int h = dht11_dat[0] + dht11_dat[1]; | |
| 146 int t = (dht11_dat[2] & 0x7F) + dht11_dat[3]; | |
| 147 t += dht11_t_offset; | |
| 148 h += dht11_h_offset; | |
| 149 | |
| 150 if ((dht11_dat[2] & 0x80) != 0) | |
| 151 t *= -1; | |
| 152 | |
| 153 dht11_temperature = t; | |
| 154 dht11_humidity = h; | |
| 155 dht11_valid = TRUE; | |
| 156 } else { | |
| 157 tries--; | |
| 158 if (tries == 0) | |
| 159 syslog(LOG_INFO, "dht11 data checksum was wrong 5 times"); | |
| 160 usleep(100000); | |
| 161 } | |
| 162 } | |
| 163 } | |
| 164 | |
| 165 | |
| 166 | |
| 167 void dht11Init(int pin, int t_offset, int h_offset) { | |
| 168 dht11_pin = pin; | |
| 169 dht11_t_offset = t_offset; | |
| 170 dht11_h_offset = h_offset; | |
| 171 } | |
| 172 | |
| 173 | |
| 174 | |
| 175 int main(int argc, char *argv[]) { | |
| 176 | |
| 177 int PIN = 3; | |
| 178 | |
| 179 if (wiringPiSetup() == -1) | |
| 180 return 0; | |
| 181 | |
| 182 dht11Init(PIN, 1, 6); | |
| 183 dht11Read(); | |
| 184 if (dht11_valid) { | |
| 185 fprintf(stdout, "DHT11: temperature %d degrees, humidity %d%%\n", dht11_temperature, dht11_humidity); | |
| 186 } else { | |
| 187 fprintf(stdout, "DHT11: no valid data or sensor not connected\n"); | |
| 188 } | |
| 189 | |
| 190 exit(0); | |
| 191 } | |
| 192 | |
| 193 #else | |
| 194 | |
| 195 int main(int argc, char *argv[]) { | |
| 196 fprintf(stderr, "This program does nothing without the wiringPi library\n"); | |
| 197 return 0; | |
| 198 } | |
| 199 | |
| 200 #endif | |
| 201 |
