made some changes
Fork of DHT by
Diff: DHT.cpp
- Revision:
- 0:9b5b3200688f
- Child:
- 1:d9116db5603f
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/DHT.cpp Mon Jul 09 19:47:43 2012 +0000 @@ -0,0 +1,233 @@ +/* + * DHT Library for Digital-output Humidity and Temperature sensors + * + * Works with DHT11, DHT22 + * SEN11301P, Grove - Temperature&Humidity Sensor (Seeed Studio) + * SEN51035P, Grove - Temperature&Humidity Sensor Pro (Seeed Studio) + * AM2302 , temperature-humidity sensor + * HM2303 , Digital-output humidity and temperature sensor + * + * Copyright (C) Wim De Roeve + * based on DHT22 sensor library by HO WING KIT + * Arduino DHT11 library + * + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documnetation files (the "Software"), to deal + * in the Software without restriction, including without limitation the rights + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell + * copies of the Software, and to permit persons to whom the Software is + * furished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS OR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN + * THE SOFTWARE. + */ + +#include "DHT.h" + +#define DHT_DATA_BIT_COUNT 41 + +DHT::DHT(PinName pin,int DHTtype) { + _pin = pin; + _DHTtype = DHTtype; + _firsttime=true; +} + +DHT::~DHT() { +} + +int DHT::readData() { + int i, j, retryCount,b; + unsigned int bitTimes[DHT_DATA_BIT_COUNT]; + + eError err = ERROR_NONE; + time_t currentTime = time(NULL); + + DigitalInOut DHT_io(_pin); + + for (i = 0; i < DHT_DATA_BIT_COUNT; i++) { + bitTimes[i] = 0; + } + + if (!_firsttime) { + if (int(currentTime - _lastReadTime) < 2) { + err = ERROR_NO_PATIENCE; + return err; + } + } else { + _firsttime=false; + _lastReadTime=currentTime; + } + retryCount = 0; + + do { + if (retryCount > 125) { + err = BUS_BUSY; + return err; + } + retryCount ++; + wait_us(2); + } while ((DHT_io==0)); + + + DHT_io.output(); + DHT_io = 0; + wait_ms(18); + DHT_io = 1; + wait_us(40); + DHT_io.input(); + + retryCount = 0; + do { + if (retryCount > 40) { + err = ERROR_NOT_PRESENT; + return err; + } + retryCount++; + wait_us(1); + } while ((DHT_io==1)); + + if (err != ERROR_NONE) { + return err; + } + + wait_us(80); + + for (i = 0; i < 5; i++) { + for (j = 0; j < 8; j++) { + + retryCount = 0; + do { + if (retryCount > 75) { + err = ERROR_DATA_TIMEOUT; + return err; + } + retryCount++; + wait_us(1); + } while (DHT_io == 0); + wait_us(40); + bitTimes[i*8+j]=DHT_io; + + int count = 0; + while (DHT_io == 1 && count < 100) { + wait_us(1); + count++; + } + } + } + DHT_io.output(); + DHT_io = 1; + for (i = 0; i < 5; i++) { + b=0; + for (j=0; j<8; j++) { + if (bitTimes[i*8+j+1] > 0) { + b |= ( 1 << (7-j)); + } + } + DHT_data[i]=b; + } + + if (DHT_data[4] == ((DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3]) & 0xFF)) { + _lastReadTime = currentTime; + _lastTemperature=CalcTemperature(); + _lastHumidity=CalcHumidity(); + + } else { + err = ERROR_CHECKSUM; + } + + return err; + +} + +float DHT::CalcTemperature() { + int v; + + switch (_DHTtype) { + case DHT11: + v = DHT_data[2]; + return float(v); + case DHT22: + v = DHT_data[2] & 0x7F; + v *= 256; + v += DHT_data[3]; + v /= 10; + if (DHT_data[2] & 0x80) + v *= -1; + return float(v); + } + return 0; +} + +float DHT::ReadHumidity() { + return _lastHumidity; +} + +float DHT::ConvertCelciustoFarenheit(float celsius) { + return celsius * 9 / 5 + 32; +} + +float DHT::ConvertCelciustoKelvin(float celsius) { + return celsius + 273.15; +} + +// dewPoint function NOAA +// reference: http://wahiduddin.net/calc/density_algorithms.htm +float DHT::CalcdewPoint(float celsius, float humidity) { + float A0= 373.15/(273.15 + celsius); + float SUM = -7.90298 * (A0-1); + SUM += 5.02808 * log10(A0); + SUM += -1.3816e-7 * (pow(10, (11.344*(1-1/A0)))-1) ; + SUM += 8.1328e-3 * (pow(10,(-3.49149*(A0-1)))-1) ; + SUM += log10(1013.246); + float VP = pow(10, SUM-3) * humidity; + float T = log(VP/0.61078); // temp var + return (241.88 * T) / (17.558-T); +} + +// delta max = 0.6544 wrt dewPoint() +// 5x faster than dewPoint() +// reference: http://en.wikipedia.org/wiki/Dew_point +float DHT::CalcdewPointFast(float celsius, float humidity) +{ + float a = 17.271; + float b = 237.7; + float temp = (a * celsius) / (b + celsius) + log(humidity/100); + float Td = (b * temp) / (a - temp); + return Td; +} + +float DHT::ReadTemperature(eScale Scale) { + if (Scale == FARENHEIT) + return ConvertCelciustoFarenheit(_lastTemperature); + else if (Scale == KELVIN) + return ConvertCelciustoKelvin(_lastTemperature); + else + return _lastTemperature; +} + +float DHT::CalcHumidity() { + int v; + + switch (_DHTtype) { + case DHT11: + v = DHT_data[0]; + return float(v); + case DHT22: + v = DHT_data[0]; + v *= 256; + v += DHT_data[1]; + v /= 10; + return float(v); + } + return 0; +} + +