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177 lines
5.1 KiB
177 lines
5.1 KiB
// -----------------------------------------------------------------------------
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// DHTXX Sensor
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// Copyright (C) 2017 by Xose Pérez <xose dot perez at gmail dot com>
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// -----------------------------------------------------------------------------
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#pragma once
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#include "Arduino.h"
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#include "BaseSensor.h"
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#define DHT_MAX_DATA 5
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#define DHT_MAX_ERRORS 5
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#define DHT_MIN_INTERVAL 2000
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#define DHT11 11
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#define DHT22 22
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#define DHT21 21
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#define AM2301 21
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class DHTSensor : public BaseSensor {
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public:
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DHTSensor(unsigned char gpio, unsigned char type, bool pull_up = false): BaseSensor() {
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_gpio = gpio;
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_type = type;
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if (pull_up) pinMode(_gpio, INPUT_PULLUP);
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_count = 2;
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}
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// Pre-read hook (usually to populate registers with up-to-date data)
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void pre() {
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if ((_last_ok > 0) && (millis() - _last_ok < DHT_MIN_INTERVAL)) {
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_error = SENSOR_ERROR_OK;
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return;
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}
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unsigned long low = 0;
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unsigned long high = 0;
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unsigned char dhtData[DHT_MAX_DATA] = {0};
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unsigned char byteInx = 0;
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unsigned char bitInx = 7;
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// Send start signal to DHT sensor
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if (++_errors > DHT_MAX_ERRORS) {
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_errors = 0;
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digitalWrite(_gpio, HIGH);
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delay(250);
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}
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pinMode(_gpio, OUTPUT);
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noInterrupts();
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digitalWrite(_gpio, LOW);
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delayMicroseconds(500);
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digitalWrite(_gpio, HIGH);
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delayMicroseconds(40);
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pinMode(_gpio, INPUT_PULLUP);
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// No errors, read the 40 data bits
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for( int k = 0; k < 41; k++ ) {
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// Starts new data transmission with >50us low signal
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low = _signal(56, LOW);
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if (low == 0) {
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_error = SENSOR_ERROR_TIMEOUT;
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return;
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}
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// Check to see if after >70us rx data is a 0 or a 1
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high = _signal(75, HIGH);
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if (high == 0) {
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_error = SENSOR_ERROR_TIMEOUT;
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return;
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}
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// Skip the first bit
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if (k == 0) continue;
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// add the current read to the output data
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// since all dhtData array where set to 0 at the start,
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// only look for "1" (>28us us)
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if (high > low) dhtData[byteInx] |= (1 << bitInx);
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// index to next byte
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if (bitInx == 0) {
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bitInx = 7;
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++byteInx;
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} else {
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--bitInx;
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}
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}
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interrupts();
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// Verify checksum
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if (dhtData[4] != ((dhtData[0] + dhtData[1] + dhtData[2] + dhtData[3]) & 0xFF)) {
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_error = SENSOR_ERROR_CRC;
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return;
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}
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// Get humidity from Data[0] and Data[1]
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if (_type == DHT11) {
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_humidity = dhtData[0];
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} else {
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_humidity = dhtData[0] * 256 + dhtData[1];
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_humidity /= 10;
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}
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// Get temp from Data[2] and Data[3]
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if (_type == DHT11) {
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_temperature = dhtData[2];
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} else {
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_temperature = (dhtData[2] & 0x7F) * 256 + dhtData[3];
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_temperature /= 10;
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if (dhtData[2] & 0x80) _temperature *= -1;
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}
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_last_ok = millis();
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_errors = 0;
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_error = SENSOR_ERROR_OK;
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}
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// Descriptive name of the sensor
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String name() {
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char buffer[20];
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snprintf(buffer, sizeof(buffer), "DHT%d @ GPIO%d", _type, _gpio);
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return String(buffer);
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}
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// Descriptive name of the slot # index
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String slot(unsigned char index) {
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return name();
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}
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// Type for slot # index
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magnitude_t type(unsigned char index) {
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_error = SENSOR_ERROR_OK;
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if (index == 0) return MAGNITUDE_TEMPERATURE;
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if (index == 1) return MAGNITUDE_HUMIDITY;
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_error = SENSOR_ERROR_OUT_OF_RANGE;
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return MAGNITUDE_NONE;
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}
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// Current value for slot # index
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double value(unsigned char index) {
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_error = SENSOR_ERROR_OK;
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if (index == 0) return _temperature;
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if (index == 1) return _humidity;
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_error = SENSOR_ERROR_OUT_OF_RANGE;
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return 0;
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}
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protected:
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unsigned long _signal(int usTimeOut, bool state) {
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unsigned long uSec = 1;
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while (digitalRead(_gpio) == state) {
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if (++uSec > usTimeOut) return 0;
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delayMicroseconds(1);
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}
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return uSec;
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}
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unsigned char _gpio;
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unsigned char _type;
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unsigned long _last_ok = 0;
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unsigned char _errors = 0;
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double _temperature;
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unsigned int _humidity;
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};
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