230 lines
6.1 KiB
C++
230 lines
6.1 KiB
C++
/*
|
|
* 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 40
|
|
|
|
DHT::DHT(PinName pin, eType DHTtype)
|
|
{
|
|
_pin = pin;
|
|
_DHTtype = DHTtype;
|
|
_firsttime = true;
|
|
}
|
|
|
|
DHT::~DHT()
|
|
{
|
|
|
|
}
|
|
|
|
eError DHT::stall(DigitalInOut &io, int const level, int const max_time)
|
|
{
|
|
int cnt = 0;
|
|
while (level == io) {
|
|
if (cnt > max_time) {
|
|
|
|
return ERROR_NO_PATIENCE;
|
|
}
|
|
cnt++;
|
|
wait_us(1);
|
|
}
|
|
return ERROR_NONE;
|
|
}
|
|
|
|
eError DHT::readData()
|
|
{
|
|
uint8_t i = 0, j = 0, b = 0, data_valid = 0;
|
|
uint32_t bit_value[DHT_DATA_BIT_COUNT] = {0};
|
|
|
|
eError err = ERROR_NONE;
|
|
time_t currentTime = time(NULL);
|
|
|
|
DigitalInOut DHT_io(_pin);
|
|
|
|
// IO must be in hi state to start
|
|
if (ERROR_NONE != stall(DHT_io, 0, 250)) {
|
|
return BUS_BUSY;
|
|
}
|
|
|
|
// start the transfer
|
|
DHT_io.output();
|
|
DHT_io = 0;
|
|
// only 500uS for DHT22 but 18ms for DHT11
|
|
(_DHTtype == 11) ? wait_us(18000) : wait_us(500);
|
|
DHT_io = 1;
|
|
wait_us(30);
|
|
DHT_io.input();
|
|
|
|
// wait till the sensor grabs the bus
|
|
if (ERROR_NONE != stall(DHT_io, 1, 40)) {
|
|
return ERROR_NOT_PRESENT;
|
|
}
|
|
// sensor should signal low 80us and then hi 80us
|
|
if (ERROR_NONE != stall(DHT_io, 0, 100)) {
|
|
return ERROR_SYNC_TIMEOUT;
|
|
}
|
|
if (ERROR_NONE != stall(DHT_io, 1, 100)) {
|
|
return ERROR_NO_PATIENCE;
|
|
}
|
|
// capture the data
|
|
for (i = 0; i < 5; i++) {
|
|
for (j = 0; j < 8; j++) {
|
|
if (ERROR_NONE != stall(DHT_io, 0, 75)) {
|
|
return ERROR_DATA_TIMEOUT;
|
|
}
|
|
// logic 0 is 28us max, 1 is 70us
|
|
wait_us(40);
|
|
bit_value[i*8+j] = DHT_io;
|
|
if (ERROR_NONE != stall(DHT_io, 1, 50)) {
|
|
return ERROR_DATA_TIMEOUT;
|
|
}
|
|
}
|
|
}
|
|
// store the data
|
|
for (i = 0; i < 5; i++) {
|
|
b=0;
|
|
for (j=0; j<8; j++) {
|
|
if (bit_value[i*8+j] == 1) {
|
|
b |= (1 << (7-j));
|
|
}
|
|
}
|
|
DHT_data[i]=b;
|
|
}
|
|
|
|
// uncomment to see the checksum error if it exists
|
|
//printf(" 0x%02x + 0x%02x + 0x%02x + 0x%02x = 0x%02x \n", DHT_data[0], DHT_data[1], DHT_data[2], DHT_data[3], DHT_data[4]);
|
|
data_valid = DHT_data[0] + DHT_data[1] + DHT_data[2] + DHT_data[3];
|
|
if (DHT_data[4] == data_valid) {
|
|
_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 const celsius)
|
|
{
|
|
return celsius * 9 / 5 + 32;
|
|
}
|
|
|
|
float DHT::ConvertCelciustoKelvin(float const celsius)
|
|
{
|
|
return celsius + 273.15;
|
|
}
|
|
|
|
// dewPoint function NOAA
|
|
// reference: http://wahiduddin.net/calc/density_algorithms.htm
|
|
float DHT::CalcdewPoint(float const celsius, float const 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 const celsius, float const 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;
|
|
}
|
|
|
|
|