Use own DHT implementation

code/espurna/dht.ino

@@ -8,20 +8,139 @@ Copyright (C) 2016-2017 by Xose Pérez <xose dot perez at gmail dot com>
 
 #if DHT_SUPPORT
 
-#include <DHT.h>
-#include <Adafruit_Sensor.h>
-
-DHT dht(DHT_PIN, DHT_TYPE, DHT_TIMING);
-
 double _dhtTemperature = 0;
 unsigned int _dhtHumidity = 0;
 
+// -----------------------------------------------------------------------------
+// HAL
+// https://github.com/gosouth/DHT22/blob/master/main/DHT22.c
+// -----------------------------------------------------------------------------
+
+#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
+
+unsigned long _getSignalLevel(unsigned char gpio, int usTimeOut, bool state) {
+	unsigned long uSec = 1;
+	while (digitalRead(gpio) == state) {
+        if (++uSec > usTimeOut) return 0;
+        delayMicroseconds(1);
+	}
+	return uSec;
+}
+
+int readDHT(unsigned char gpio, unsigned char type) {
+
+    static unsigned long last_ok = 0;
+    if (millis() - last_ok < DHT_MIN_INTERVAL) return DHT_OK;
+
+    unsigned long low = 0;
+    unsigned long high = 0;
+
+    static unsigned char errors = 0;
+    uint8_t dhtData[DHT_MAX_DATA] = {0};
+    uint8_t byteInx = 0;
+    uint8_t bitInx = 7;
+
+	// Send start signal to DHT sensor
+	if (++errors > DHT_MAX_ERRORS) {
+        errors = 0;
+        digitalWrite(gpio, HIGH);
+        delay(250);
+    }
+    pinMode(gpio, OUTPUT);
+	digitalWrite(gpio, LOW);
+	delay(20);
+    noInterrupts();
+    digitalWrite(gpio, HIGH);
+    delayMicroseconds(40);
+    pinMode(gpio, INPUT_PULLUP);
+    delayMicroseconds(10);
+
+	// DHT will keep the line low for 80 us and then high for 80us
+	low = _getSignalLevel(gpio, 85, LOW);
+	if (low==0) return DHT_TIMEOUT_ERROR;
+	high = _getSignalLevel(gpio, 85, HIGH);
+    if (high==0) return DHT_TIMEOUT_ERROR;
+
+	// No errors, read the 40 data bits
+	for( int k = 0; k < 40; k++ ) {
+
+		// Starts new data transmission with >50us low signal
+		low = _getSignalLevel(gpio, 56, LOW);
+		if (low==0) return DHT_TIMEOUT_ERROR;
+
+		// Check to see if after >70us rx data is a 0 or a 1
+		high = _getSignalLevel(gpio, 75, HIGH);
+        if (high==0) return DHT_TIMEOUT_ERROR;
+
+		// 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)) {
+        return DHT_CHECKSUM_ERROR;
+    }
+
+	// Get humidity from Data[0] and Data[1]
+    if (type == DHT11) {
+        _dhtHumidity = dhtData[0];
+    } else {
+	   _dhtHumidity = dhtData[0] * 256 + dhtData[1];
+	   _dhtHumidity /= 10;
+    }
+
+	// Get temp from Data[2] and Data[3]
+    if (type == DHT11) {
+        _dhtTemperature = dhtData[2];
+    } else {
+        _dhtTemperature = (dhtData[2] & 0x7F) * 256 + dhtData[3];
+        _dhtTemperature /= 10;
+        if (dhtData[2] & 0x80) _dhtTemperature *= -1;
+    }
+
+    last_ok = millis();
+    errors = 0;
+	return DHT_OK;
+
+}
+
+int readDHT() {
+    return readDHT(DHT_PIN, DHT_TYPE);
+}
+
 // -----------------------------------------------------------------------------
 // Values
 // -----------------------------------------------------------------------------
 
+double getDHTTemperature(bool celsius) {
+    return celsius ? _dhtTemperature : _dhtTemperature * 1.8 + 32;
+}
+
 double getDHTTemperature() {
-    return _dhtTemperature;
+    return getDHTTemperature(true);
 }
 
 unsigned int getDHTHumidity() {
@@ -30,8 +149,6 @@ unsigned int getDHTHumidity() {
 
 void dhtSetup() {
 
-    dht.begin();
-
     #if WEB_SUPPORT
         apiRegister(DHT_TEMPERATURE_TOPIC, DHT_TEMPERATURE_TOPIC, [](char * buffer, size_t len) {
             dtostrf(_dhtTemperature, 1-len, 1, buffer);
@@ -50,21 +167,12 @@ void dhtLoop() {
     if ((millis() - last_update > DHT_UPDATE_INTERVAL) || (last_update == 0)) {
         last_update = millis();
 
-        unsigned char tmpUnits = getSetting("tmpUnits", TMP_UNITS).toInt();
-
         // Read sensor data
-        double h = dht.readHumidity();
-        double t = dht.readTemperature(tmpUnits == TMP_FAHRENHEIT);
-
-        // Check if readings are valid
-        if (isnan(h) || isnan(t)) {
-
-            DEBUG_MSG_P(PSTR("[DHT] Error reading sensor\n"));
-
-        } else {
+        if (readDHT(DHT_PIN, DHT_TYPE) == DHT_OK) {
 
-            _dhtTemperature = t;
-            _dhtHumidity = h;
+            unsigned char tmpUnits = getSetting("tmpUnits", TMP_UNITS).toInt();
+            double t = getDHTTemperature(tmpUnits == TMP_CELSIUS);
+            unsigned int h = getDHTHumidity();
 
             char temperature[6];
             char humidity[6];

code/platformio.ini

@@ -13,8 +13,6 @@ build_flags_1m = ${common.build_flags} -Wl,-Tesp8266.flash.1m0.ld
 #https://github.com/me-no-dev/ESPAsyncTCP#9b0cc37 // 2.3.0 compatible
 #https://github.com/me-no-dev/ESPAsyncTCP#3795e16 // 2.4.0-rc2 compatible
 lib_deps =
-    DHT sensor library
-    Adafruit Unified Sensor
     https://github.com/xoseperez/Time
     ArduinoJson
     https://github.com/me-no-dev/ESPAsyncTCP#9b0cc37