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Emanuele Trabattoni
2024-06-22 10:44:55 +02:00
commit 1d123f3ff2
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lib/DHT/DHT.cpp Normal file
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/*
* 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;
}