Fork of the espurna firmware for `mhsw` switches
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// -----------------------------------------------------------------------------
// DHT Sensor
// -----------------------------------------------------------------------------
#pragma once
#include "Arduino.h"
#include "BaseSensor.h"
#define DHT_MAX_DATA 5
#define DHT_MAX_ERRORS 5
#define DHT_MIN_INTERVAL 2000
#define DHT_OK 0
#define DHT_CHECKSUM_ERROR -1
#define DHT_TIMEOUT_ERROR -2
#define DHT11 11
#define DHT22 22
#define DHT21 21
#define AM2301 21
class DHTSensor : public BaseSensor {
public:
DHTSensor(unsigned char gpio, unsigned char type, bool pull_up = false): BaseSensor() {
_gpio = gpio;
_type = type;
if (pull_up) pinMode(_gpio, INPUT_PULLUP);
_count = 2;
}
// Pre-read hook (usually to populate registers with up-to-date data)
void pre() {
if ((_last_ok > 0) && (millis() - _last_ok < DHT_MIN_INTERVAL)) {
_error = SENSOR_ERROR_OK;
return;
}
unsigned long low = 0;
unsigned long high = 0;
unsigned char dhtData[DHT_MAX_DATA] = {0};
unsigned char byteInx = 0;
unsigned char bitInx = 7;
// Send start signal to DHT sensor
if (++_errors > DHT_MAX_ERRORS) {
_errors = 0;
digitalWrite(_gpio, HIGH);
delay(250);
}
pinMode(_gpio, OUTPUT);
noInterrupts();
digitalWrite(_gpio, LOW);
delayMicroseconds(500);
digitalWrite(_gpio, HIGH);
delayMicroseconds(40);
pinMode(_gpio, INPUT_PULLUP);
// No errors, read the 40 data bits
for( int k = 0; k < 41; k++ ) {
// Starts new data transmission with >50us low signal
low = _signal(56, LOW);
if (low == 0) {
_error = DHT_TIMEOUT_ERROR;
return;
}
// Check to see if after >70us rx data is a 0 or a 1
high = _signal(75, HIGH);
if (high == 0) {
_error = DHT_TIMEOUT_ERROR;
return;
}
// Skip the first bit
if (k == 0) continue;
// add the current read to the output data
// since all dhtData array where set to 0 at the start,
// only look for "1" (>28us us)
if (high > low) dhtData[byteInx] |= (1 << bitInx);
// index to next byte
if (bitInx == 0) {
bitInx = 7;
++byteInx;
} else {
--bitInx;
}
}
interrupts();
// Verify checksum
if (dhtData[4] != ((dhtData[0] + dhtData[1] + dhtData[2] + dhtData[3]) & 0xFF)) {
_error = DHT_CHECKSUM_ERROR;
return;
}
// Get humidity from Data[0] and Data[1]
if (_type == DHT11) {
_humidity = dhtData[0];
} else {
_humidity = dhtData[0] * 256 + dhtData[1];
_humidity /= 10;
}
// Get temp from Data[2] and Data[3]
if (_type == DHT11) {
_temperature = dhtData[2];
} else {
_temperature = (dhtData[2] & 0x7F) * 256 + dhtData[3];
_temperature /= 10;
if (dhtData[2] & 0x80) _temperature *= -1;
}
_last_ok = millis();
_errors = 0;
_error = SENSOR_ERROR_OK;
}
// Descriptive name of the sensor
String name() {
char buffer[20];
snprintf(buffer, sizeof(buffer), "DHT%d @ GPIO%d", _type, _gpio);
return String(buffer);
}
// Descriptive name of the slot # index
String slot(unsigned char index) {
return name();
}
// Type for slot # index
magnitude_t type(unsigned char index) {
_error = SENSOR_ERROR_OK;
if (index == 0) return MAGNITUDE_TEMPERATURE;
if (index == 1) return MAGNITUDE_HUMIDITY;
_error = SENSOR_ERROR_OUT_OF_RANGE;
return MAGNITUDE_NONE;
}
// Current value for slot # index
double value(unsigned char index) {
_error = SENSOR_ERROR_OK;
if (index == 0) return _temperature;
if (index == 1) return _humidity;
_error = SENSOR_ERROR_OUT_OF_RANGE;
return 0;
}
protected:
unsigned long _signal(int usTimeOut, bool state) {
unsigned long uSec = 1;
while (digitalRead(_gpio) == state) {
if (++uSec > usTimeOut) return 0;
delayMicroseconds(1);
}
return uSec;
}
unsigned char _gpio;
unsigned char _type;
unsigned long _last_ok = 0;
unsigned char _errors = 0;
double _temperature;
unsigned int _humidity;
};