Mercurial > mbsePi-apps / file comparison
comparison: lib/dht11.c
lib/dht11.c
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- 89dd2b691701
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| 1 /***************************************************************************** | |
| 2 * Copyright (C) 2008-2014 | |
| 3 * | |
| 4 * Michiel Broek <mbroek at mbse dot eu> | |
| 5 * | |
| 6 * This file is part of the mbsePi-apps | |
| 7 * | |
| 8 * Parts original by CurlyMo from the pilight project. | |
| 9 * | |
| 10 * This is free software; you can redistribute it and/or modify it | |
| 11 * under the terms of the GNU General Public License as published by the | |
| 12 * Free Software Foundation; either version 2, or (at your option) any | |
| 13 * later version. | |
| 14 * | |
| 15 * mbsePi-apps is distributed in the hope that it will be useful, but | |
| 16 * WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 18 * General Public License for more details. | |
| 19 * | |
| 20 * You should have received a copy of the GNU General Public License | |
| 21 * along with EC-65K; see the file COPYING. If not, write to the Free | |
| 22 * Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. | |
| 23 *****************************************************************************/ | |
| 24 | |
| 25 #include "../config.h" | |
| 26 #include "mbselib.h" | |
| 27 | |
| 28 #ifdef HAVE_WIRINGPI_H | |
| 29 | |
| 30 #define MAXTIMINGS 100 | |
| 31 | |
| 32 int dht11_pin = -1; | |
| 33 int dht11_temperature = -1; | |
| 34 int dht11_humidity = -1; | |
| 35 int dht11_valid = false; | |
| 36 int dht11_t_offset = 0; | |
| 37 int dht11_h_offset = 0; | |
| 38 | |
| 39 | |
| 40 | |
| 41 static uint8_t sizecvt(const int read_value) { | |
| 42 /* | |
| 43 * digitalRead() and friends from wiringpi are defined as returning a value | |
| 44 * < 256. However, they are returned as int() types. This is a safety function | |
| 45 */ | |
| 46 if (read_value > 255 || read_value < 0) { | |
| 47 syslog(LOG_NOTICE, "invalid data from wiringPi library"); | |
| 48 } | |
| 49 | |
| 50 return (uint8_t)read_value; | |
| 51 } | |
| 52 | |
| 53 | |
| 54 | |
| 55 /* | |
| 56 * DHT11 sensor read. This should be used in a thread loop. | |
| 57 */ | |
| 58 void dht11Read(void) { | |
| 59 int tries = 5; | |
| 60 unsigned short got_correct_data = 0; | |
| 61 | |
| 62 if (dht11_pin == -1) | |
| 63 return; | |
| 64 | |
| 65 while (tries && !got_correct_data) { | |
| 66 uint8_t laststate = HIGH; | |
| 67 uint8_t counter = 0; | |
| 68 uint8_t j = 0, i = 0; | |
| 69 int dht11_dat[5] = {0,0,0,0,0}; | |
| 70 | |
| 71 /* | |
| 72 * Select output mode to send the start signal. | |
| 73 */ | |
| 74 pinMode(dht11_pin, OUTPUT); | |
| 75 digitalWrite(dht11_pin, HIGH); | |
| 76 usleep(1000); | |
| 77 | |
| 78 /* | |
| 79 * Low for at least 18 milliseconds | |
| 80 */ | |
| 81 digitalWrite(dht11_pin, LOW); | |
| 82 usleep(20000); | |
| 83 digitalWrite(dht11_pin, HIGH); | |
| 84 pinMode(dht11_pin, INPUT); | |
| 85 | |
| 86 /* | |
| 87 * Detect change and read data | |
| 88 */ | |
| 89 for (i=0; i<MAXTIMINGS; i++) { | |
| 90 counter = 0; | |
| 91 delayMicroseconds(10); | |
| 92 while (sizecvt(digitalRead(dht11_pin)) == laststate) { | |
| 93 counter++; | |
| 94 delayMicroseconds(1); | |
| 95 if (counter == 255) { | |
| 96 break; | |
| 97 } | |
| 98 } | |
| 99 laststate = sizecvt(digitalRead(dht11_pin)); | |
| 100 | |
| 101 if (counter == 255) | |
| 102 break; | |
| 103 | |
| 104 /* | |
| 105 * ignore first 3 transitions | |
| 106 */ | |
| 107 if ((i >= 4) && (i%2 == 0)) { | |
| 108 | |
| 109 // shove each bit into the storage bytes | |
| 110 dht11_dat[(int)((double)j/8)] <<= 1; | |
| 111 if (counter > 16) | |
| 112 dht11_dat[(int)((double)j/8)] |= 1; | |
| 113 j++; | |
| 114 } | |
| 115 } | |
| 116 | |
| 117 /* | |
| 118 * If there is no sensor, j = 0 | |
| 119 */ | |
| 120 if ((counter == 255) && (j == 0)) { | |
| 121 if (dht11_temperature != -1) { | |
| 122 syslog(LOG_NOTICE, "dht11 sensor disappeared"); | |
| 123 } | |
| 124 dht11_temperature = -1; | |
| 125 dht11_humidity = -1; | |
| 126 dht11_valid = false; | |
| 127 } else { | |
| 128 | |
| 129 /* | |
| 130 * check we read 40 bits (8bit x 5 ) + verify checksum in the last byte | |
| 131 * print it out if data is good | |
| 132 */ | |
| 133 if ((j >= 40) && (dht11_dat[4] == ((dht11_dat[0] + dht11_dat[1] + dht11_dat[2] + dht11_dat[3]) & 0xFF))) { | |
| 134 got_correct_data = 1; | |
| 135 | |
| 136 int h = dht11_dat[0] + dht11_dat[1]; | |
| 137 int t = (dht11_dat[2] & 0x7F) + dht11_dat[3]; | |
| 138 t += dht11_t_offset; | |
| 139 h += dht11_h_offset; | |
| 140 | |
| 141 if ((dht11_dat[2] & 0x80) != 0) | |
| 142 t *= -1; | |
| 143 | |
| 144 dht11_temperature = t; | |
| 145 dht11_humidity = h; | |
| 146 dht11_valid = true; | |
| 147 } else { | |
| 148 tries--; | |
| 149 if (tries == 0) | |
| 150 syslog(LOG_INFO, "dht11 data checksum was wrong 5 times"); | |
| 151 usleep(100000); | |
| 152 } | |
| 153 } | |
| 154 } | |
| 155 } | |
| 156 | |
| 157 | |
| 158 | |
| 159 void dht11Init(int pin, int t_offset, int h_offset) { | |
| 160 dht11_pin = pin; | |
| 161 dht11_t_offset = t_offset; | |
| 162 dht11_h_offset = h_offset; | |
| 163 } | |
| 164 | |
| 165 | |
| 166 #endif | |
| 167 |
