Tristan Hughes / RHT03

An eddied version of http://mbed.org/users/crazystick/code/DHT22/ for LPC11U24. All printf statements are removed and features requiring the real time clock are removed.

Dependents:   RHT03_HelloWorld IOT_sensor_nfc CanSat_Alex cansat_alex_v1 ... more

RHT03.cpp@5:153e20f26d54, 2012-08-29 (annotated)

Committer:
tristanjph
Date:
Wed Aug 29 14:38:08 2012 +0000
Revision:
5:153e20f26d54
Parent:
4:e9fe691122c1 
Documentation update

Who changed what in which revision?

UserRevisionLine numberNew contents of line
tristanjph 1:2bd5cffd60d0 1 /*
tristanjph 1:2bd5cffd60d0 2 RHT22.cpp - RHT22 sensor library
tristanjph 1:2bd5cffd60d0 3 Developed by HO WING KIT
tristanjph 1:2bd5cffd60d0 4 Modifications by Paul Adams
tristanjph 4:e9fe691122c1 5 More modifications by Tristan Hughes
tristanjph 1:2bd5cffd60d0 6
tristanjph 1:2bd5cffd60d0 7 This library is free software; you can redistribute it and / or
tristanjph 1:2bd5cffd60d0 8 modify it under the terms of the GNU Leser General Public
tristanjph 1:2bd5cffd60d0 9 License as published by the Free Software Foundation; either
tristanjph 1:2bd5cffd60d0 10 version 2.1 of the License, or (at your option) any later version.
tristanjph 1:2bd5cffd60d0 11
tristanjph 1:2bd5cffd60d0 12 This library is distributed in the hope that it will be useful,
tristanjph 1:2bd5cffd60d0 13 but WITHOUT ANY WARRENTY; without even the implied warranty of
tristanjph 1:2bd5cffd60d0 14 MERCHANTABILITY or FITNESS FOR A PATRICULAR PURPOSE. See the GNU
tristanjph 1:2bd5cffd60d0 15 Lesser General Public License for more details.
tristanjph 1:2bd5cffd60d0 16
tristanjph 1:2bd5cffd60d0 17 You should have received a copy of the GNU Lesser General Public
tristanjph 1:2bd5cffd60d0 18 License along with this library; if not, write to the Free Software
tristanjph 1:2bd5cffd60d0 19 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
tristanjph 1:2bd5cffd60d0 20
tristanjph 1:2bd5cffd60d0 21
tristanjph 1:2bd5cffd60d0 22 Humidity and Temperature Sensor RHT22 info found at
tristanjph 1:2bd5cffd60d0 23 http://www.sparkfun.com/products/10167
tristanjph 1:2bd5cffd60d0 24 same as RHT03 http://www.humiditycn.com
tristanjph 1:2bd5cffd60d0 25
tristanjph 1:2bd5cffd60d0 26 Version 0.1: 8-Jan-2011 by Ho Wing Kit
tristanjph 1:2bd5cffd60d0 27 Version 0.2: 29-Mar-2012 by Paul Adams
tristanjph 1:2bd5cffd60d0 28
tristanjph 1:2bd5cffd60d0 29 Additional Credit: All the commenters on http://www.sparkfun.com/products/10167
tristanjph 1:2bd5cffd60d0 30
tristanjph 1:2bd5cffd60d0 31 */
tristanjph 1:2bd5cffd60d0 32
tristanjph 1:2bd5cffd60d0 33 #include "RHT03.h"
tristanjph 1:2bd5cffd60d0 34
tristanjph 1:2bd5cffd60d0 35
tristanjph 1:2bd5cffd60d0 36 // This should be 40, but the sensor is adding an extra bit at the start
tristanjph 1:2bd5cffd60d0 37 #define RHT03_DATA_BIT_COUNT 41
tristanjph 1:2bd5cffd60d0 38
tristanjph 1:2bd5cffd60d0 39 RHT03::RHT03(PinName Data) {
tristanjph 1:2bd5cffd60d0 40
tristanjph 1:2bd5cffd60d0 41 _data = Data; // Set Data Pin
tristanjph 1:2bd5cffd60d0 42 _lastReadTime = time(NULL);
tristanjph 1:2bd5cffd60d0 43 _lastHumidity = 0;
tristanjph 1:2bd5cffd60d0 44 _lastTemperature = RHT03_ERROR_VALUE;
tristanjph 1:2bd5cffd60d0 45 }
tristanjph 1:2bd5cffd60d0 46
tristanjph 1:2bd5cffd60d0 47 RHT03::~RHT03() {
tristanjph 1:2bd5cffd60d0 48 }
tristanjph 1:2bd5cffd60d0 49
tristanjph 1:2bd5cffd60d0 50 RHT03_ERROR RHT03::readData() {
tristanjph 1:2bd5cffd60d0 51 int i, j, retryCount;
tristanjph 1:2bd5cffd60d0 52 int currentTemperature=0;
tristanjph 1:2bd5cffd60d0 53 int currentHumidity=0;
tristanjph 1:2bd5cffd60d0 54 unsigned int checkSum = 0, csPart1, csPart2, csPart3, csPart4;
tristanjph 1:2bd5cffd60d0 55 unsigned int bitTimes[RHT03_DATA_BIT_COUNT];
tristanjph 1:2bd5cffd60d0 56 RHT03_ERROR err = RHT_ERROR_NONE;
tristanjph 1:2bd5cffd60d0 57 time_t currentTime = time(NULL);
tristanjph 1:2bd5cffd60d0 58
tristanjph 1:2bd5cffd60d0 59 DigitalInOut DATA(_data);
tristanjph 1:2bd5cffd60d0 60
tristanjph 1:2bd5cffd60d0 61 for (i = 0; i < RHT03_DATA_BIT_COUNT; i++) {
tristanjph 1:2bd5cffd60d0 62 bitTimes[i] = 0;
tristanjph 1:2bd5cffd60d0 63 }
tristanjph 1:2bd5cffd60d0 64
tristanjph 1:2bd5cffd60d0 65 // if (int(currentTime - _lastReadTime) < 2) {
tristanjph 1:2bd5cffd60d0 66 // printf("RHT22 Error Access Time < 2s");
tristanjph 1:2bd5cffd60d0 67 // err = RHT_ERROR_TOO_QUICK;
tristanjph 1:2bd5cffd60d0 68 // }
tristanjph 1:2bd5cffd60d0 69 retryCount = 0;
tristanjph 1:2bd5cffd60d0 70 // Pin needs to start HIGH, wait unit it is HIGH with a timeout
tristanjph 1:2bd5cffd60d0 71 do {
tristanjph 1:2bd5cffd60d0 72 if (retryCount > 125) {
tristanjph 1:2bd5cffd60d0 73 //pc1.printf("RHT22 Bus busy!");
tristanjph 1:2bd5cffd60d0 74 err = RHT_BUS_HUNG;
tristanjph 1:2bd5cffd60d0 75 return err;
tristanjph 1:2bd5cffd60d0 76 }
tristanjph 1:2bd5cffd60d0 77 retryCount ++;
tristanjph 1:2bd5cffd60d0 78 wait_us(2);
tristanjph 1:2bd5cffd60d0 79 } while (DATA==0); // exit on RHT22 return 'High' Signal within 250us
tristanjph 1:2bd5cffd60d0 80
tristanjph 1:2bd5cffd60d0 81 // Send the activate pulse
tristanjph 1:2bd5cffd60d0 82 // Step 1: MCU send out start signal to RHT22 and RHT22 send
tristanjph 1:2bd5cffd60d0 83 // response signal to MCU.
tristanjph 1:2bd5cffd60d0 84 // If always signal high-voltage-level, it means RHT22 is not
tristanjph 1:2bd5cffd60d0 85 // working properly, please check the electrical connection status.
tristanjph 1:2bd5cffd60d0 86 //
tristanjph 1:2bd5cffd60d0 87 DATA.output(); // set pin to output data
tristanjph 1:2bd5cffd60d0 88 DATA = 0; // MCU send out start signal to RHT22
tristanjph 1:2bd5cffd60d0 89 wait_ms(18); // 18 ms wait (spec: at least 1ms)
tristanjph 1:2bd5cffd60d0 90 DATA = 1; // MCU pull up
tristanjph 1:2bd5cffd60d0 91 wait_us(40);
tristanjph 1:2bd5cffd60d0 92 DATA.input(); // set pin to receive data
tristanjph 1:2bd5cffd60d0 93 // Find the start of the ACK Pulse
tristanjph 1:2bd5cffd60d0 94 retryCount = 0;
tristanjph 1:2bd5cffd60d0 95 do {
tristanjph 1:2bd5cffd60d0 96 if (retryCount > 40) { // (Spec is 20-40 us high)
tristanjph 1:2bd5cffd60d0 97 //pc1.printf("RHT22 not responding!");
tristanjph 1:2bd5cffd60d0 98 err = RHT_ERROR_NOT_PRESENT;
tristanjph 1:2bd5cffd60d0 99 return err;
tristanjph 1:2bd5cffd60d0 100 }
tristanjph 1:2bd5cffd60d0 101 retryCount++;
tristanjph 1:2bd5cffd60d0 102 wait_us(1);
tristanjph 1:2bd5cffd60d0 103 } while (DATA==1); // Exit on RHT22 pull low within 40us
tristanjph 1:2bd5cffd60d0 104 if (err != RHT_ERROR_NONE) {
tristanjph 1:2bd5cffd60d0 105 // initialisation failed
tristanjph 1:2bd5cffd60d0 106 return err;
tristanjph 1:2bd5cffd60d0 107 }
tristanjph 1:2bd5cffd60d0 108 wait_us(80); // RHT pull up ready to transmit data
tristanjph 1:2bd5cffd60d0 109
tristanjph 1:2bd5cffd60d0 110 /*
tristanjph 1:2bd5cffd60d0 111 if (DATA == 0) {
tristanjph 1:2bd5cffd60d0 112 printf("RHT22 not ready!");
tristanjph 1:2bd5cffd60d0 113 err = RHT_ERROR_ACK_TOO_LONG;
tristanjph 1:2bd5cffd60d0 114 return err;
tristanjph 1:2bd5cffd60d0 115 }
tristanjph 1:2bd5cffd60d0 116 */
tristanjph 1:2bd5cffd60d0 117
tristanjph 1:2bd5cffd60d0 118 // Reading the 5 byte data stream
tristanjph 1:2bd5cffd60d0 119 // Step 2: RHT22 send data to MCU
tristanjph 1:2bd5cffd60d0 120 // Start bit -> low volage within 50us (actually could be anything from 35-75us)
tristanjph 1:2bd5cffd60d0 121 // 0 -> high volage within 26-28us (actually could be 10-40us)
tristanjph 1:2bd5cffd60d0 122 // 1 -> high volage within 70us (actually could be 60-85us)
tristanjph 1:2bd5cffd60d0 123 // See http://www.sparkfun.com/products/10167#comment-4f118d6e757b7f536e000000
tristanjph 1:2bd5cffd60d0 124
tristanjph 1:2bd5cffd60d0 125
tristanjph 1:2bd5cffd60d0 126 for (i = 0; i < 5; i++) {
tristanjph 1:2bd5cffd60d0 127 for (j = 0; j < 8; j++) {
tristanjph 1:2bd5cffd60d0 128 // Instead of relying on the data sheet, just wait while the RHT03 pin is low
tristanjph 1:2bd5cffd60d0 129 retryCount = 0;
tristanjph 1:2bd5cffd60d0 130 do {
tristanjph 1:2bd5cffd60d0 131 if (retryCount > 75) {
tristanjph 1:2bd5cffd60d0 132 //pc1.printf("RHT22 timeout waiting for data!");
tristanjph 1:2bd5cffd60d0 133 err = RHT_ERROR_DATA_TIMEOUT;
tristanjph 1:2bd5cffd60d0 134 }
tristanjph 1:2bd5cffd60d0 135 retryCount++;
tristanjph 1:2bd5cffd60d0 136 wait_us(1);
tristanjph 1:2bd5cffd60d0 137 } while (DATA == 0);
tristanjph 1:2bd5cffd60d0 138 // We now wait for 40us
tristanjph 1:2bd5cffd60d0 139 wait_us(40);
tristanjph 1:2bd5cffd60d0 140 if (DATA == 1) {
tristanjph 1:2bd5cffd60d0 141 // If pin is still high, bit value is a 1
tristanjph 1:2bd5cffd60d0 142 bitTimes[i*8+j] = 1;
tristanjph 1:2bd5cffd60d0 143 } else {
tristanjph 1:2bd5cffd60d0 144 // The bit value is a 0
tristanjph 1:2bd5cffd60d0 145 bitTimes[i*8+j] = 0;
tristanjph 1:2bd5cffd60d0 146 }
tristanjph 1:2bd5cffd60d0 147 int count = 0;
tristanjph 1:2bd5cffd60d0 148 while (DATA == 1 && count < 100) {
tristanjph 1:2bd5cffd60d0 149 wait_us(1); // Delay for 1 microsecond
tristanjph 1:2bd5cffd60d0 150 count++;
tristanjph 1:2bd5cffd60d0 151 }
tristanjph 1:2bd5cffd60d0 152 }
tristanjph 1:2bd5cffd60d0 153 }
tristanjph 1:2bd5cffd60d0 154 // Re-init RHT22 pin
tristanjph 1:2bd5cffd60d0 155 DATA.output();
tristanjph 1:2bd5cffd60d0 156 DATA = 1;
tristanjph 1:2bd5cffd60d0 157
tristanjph 1:2bd5cffd60d0 158 // Now bitTimes have the actual bits
tristanjph 1:2bd5cffd60d0 159 // that were needed to find the end of each data bit
tristanjph 1:2bd5cffd60d0 160 // Note: the bits are offset by one from the data sheet, not sure why
tristanjph 1:2bd5cffd60d0 161 currentHumidity = 0;
tristanjph 1:2bd5cffd60d0 162 currentTemperature = 0;
tristanjph 1:2bd5cffd60d0 163 checkSum = 0;
tristanjph 1:2bd5cffd60d0 164 // First 16 bits is Humidity
tristanjph 1:2bd5cffd60d0 165 for (i=0; i<16; i++) {
tristanjph 1:2bd5cffd60d0 166 //printf("bit %d: %d ", i, bitTimes[i+1]);
tristanjph 1:2bd5cffd60d0 167 if (bitTimes[i+1] > 0) {
tristanjph 1:2bd5cffd60d0 168 currentHumidity |= ( 1 << (15-i));
tristanjph 1:2bd5cffd60d0 169 }
tristanjph 1:2bd5cffd60d0 170 }
tristanjph 1:2bd5cffd60d0 171
tristanjph 1:2bd5cffd60d0 172 // Second 16 bits is Temperature
tristanjph 1:2bd5cffd60d0 173 for (i=0; i<16; i ++) {
tristanjph 1:2bd5cffd60d0 174 //printf("bit %d: %d ", i+16, bitTimes[i+17]);
tristanjph 1:2bd5cffd60d0 175 if (bitTimes[i+17] > 0) {
tristanjph 1:2bd5cffd60d0 176 currentTemperature |= (1 <<(15-i));
tristanjph 1:2bd5cffd60d0 177 }
tristanjph 1:2bd5cffd60d0 178 }
tristanjph 1:2bd5cffd60d0 179
tristanjph 1:2bd5cffd60d0 180 // Last 8 bit is Checksum
tristanjph 1:2bd5cffd60d0 181 for (i=0; i<8; i++) {
tristanjph 1:2bd5cffd60d0 182 //printf("bit %d: %d ", i+32, bitTimes[i+33]);
tristanjph 1:2bd5cffd60d0 183 if (bitTimes[i+33] > 0) {
tristanjph 1:2bd5cffd60d0 184 checkSum |= (1 << (7-i));
tristanjph 1:2bd5cffd60d0 185 }
tristanjph 1:2bd5cffd60d0 186 }
tristanjph 1:2bd5cffd60d0 187
tristanjph 1:2bd5cffd60d0 188 _lastHumidity = (float(currentHumidity) / 10.0);
tristanjph 1:2bd5cffd60d0 189
tristanjph 1:2bd5cffd60d0 190 // if first bit of currentTemperature is 1, it is negative value.
tristanjph 1:2bd5cffd60d0 191 if ((currentTemperature & 0x8000)==0x8000) {
tristanjph 1:2bd5cffd60d0 192 _lastTemperature = (float(currentTemperature & 0x7FFF) / 10.0) * -1.0;
tristanjph 1:2bd5cffd60d0 193 } else {
tristanjph 1:2bd5cffd60d0 194 _lastTemperature = float(currentTemperature) / 10.0;
tristanjph 1:2bd5cffd60d0 195 }
tristanjph 1:2bd5cffd60d0 196
tristanjph 1:2bd5cffd60d0 197 // Calculate Check Sum
tristanjph 1:2bd5cffd60d0 198 csPart1 = currentHumidity >> 8;
tristanjph 1:2bd5cffd60d0 199 csPart2 = currentHumidity & 0xFF;
tristanjph 1:2bd5cffd60d0 200 csPart3 = currentTemperature >> 8;
tristanjph 1:2bd5cffd60d0 201 csPart4 = currentTemperature & 0xFF;
tristanjph 1:2bd5cffd60d0 202 if (checkSum == ((csPart1 + csPart2 + csPart3 + csPart4) & 0xFF)) {
tristanjph 1:2bd5cffd60d0 203 _lastReadTime = currentTime;
tristanjph 1:2bd5cffd60d0 204 //pc1.printf("OK-->Temperature:%f, Humidity:%f\r\n", _lastTemperature, _lastHumidity);
tristanjph 1:2bd5cffd60d0 205 err = RHT_ERROR_NONE;
tristanjph 1:2bd5cffd60d0 206 } else {
tristanjph 1:2bd5cffd60d0 207 //pc1.printf("RHT22 Checksum error!\n");
tristanjph 1:2bd5cffd60d0 208 //pc1.printf("Calculate check sum is %d\n",(csPart1 + csPart2 + csPart3 + csPart4) & 0xFF);
tristanjph 1:2bd5cffd60d0 209 //pc1.printf("Reading check sum is %d",checkSum);
tristanjph 1:2bd5cffd60d0 210 err = RHT_ERROR_CHECKSUM;
tristanjph 1:2bd5cffd60d0 211 }
tristanjph 1:2bd5cffd60d0 212 return err;
tristanjph 1:2bd5cffd60d0 213 }
tristanjph 1:2bd5cffd60d0 214
tristanjph 1:2bd5cffd60d0 215 float RHT03::getTemperatureC() {
tristanjph 1:2bd5cffd60d0 216 return _lastTemperature;
tristanjph 1:2bd5cffd60d0 217 }
tristanjph 1:2bd5cffd60d0 218
tristanjph 1:2bd5cffd60d0 219 float RHT03::getHumidity() {
tristanjph 1:2bd5cffd60d0 220 return _lastHumidity;
tristanjph 0:24f59e3759a1 221 }