added option to correct temperature value read from ds18b20 or dth22 sensor

code/espurna/config/general.h

@@ -239,6 +239,7 @@ PROGMEM const char* const custom_reset_string[] = {
 #define TMP_CELSIUS             0
 #define TMP_FAHRENHEIT          1
 #define TMP_UNITS               TMP_CELSIUS // Temperature units (TMP_CELSIUS | TMP_FAHRENHEIT)
+#define TMP_CORRECTION          0.0
 
 //------------------------------------------------------------------------------
 // LED

code/espurna/dht.ino

@@ -171,7 +171,8 @@ void dhtLoop() {
         if (readDHT(DHT_PIN, DHT_TYPE) == DHT_OK) {
 
             unsigned char tmpUnits = getSetting("tmpUnits", TMP_UNITS).toInt();
-            double t = getDHTTemperature(tmpUnits == TMP_CELSIUS);
+						double tmpCorrection = getSetting("tmpCorrection", TMP_CORRECTION).toFloat();
+            double t = getDHTTemperature(tmpUnits == TMP_CELSIUS) + tmpCorrection;						
             unsigned int h = getDHTHumidity();
 
             char temperature[6];

code/espurna/ds18b20.ino

@@ -74,17 +74,21 @@ void dsLoop() {
         last_update = millis();
 
         unsigned char tmpUnits = getSetting("tmpUnits", TMP_UNITS).toInt();
+        double tmpCorrection = getSetting("tmpCorrection", TMP_CORRECTION).toFloat();
 
         // Read sensor data
         double t = (tmpUnits == TMP_CELSIUS) ? ds18b20.getTempCByIndex(0) : ds18b20.getTempFByIndex(0);
 
+        // apply temperature reading correction
+        t = t + tmpCorrection;
+
         // Check if readings are valid
         if (isnan(t) || t < -50) {
 
             DEBUG_MSG_P(PSTR("[DS18B20] Error reading sensor\n"));
 
         } else {
-            
+
             //If the new temperature is different from the last
             if (fabs(t - last_temperature) >= DS18B20_UPDATE_ON_CHANGE) {
                 last_temperature = t;

code/espurna/web.ino

@@ -564,6 +564,7 @@ void _wsStart(uint32_t client_id) {
         root["apiRealTime"] = getSetting("apiRealTime", API_REAL_TIME_VALUES).toInt() == 1;
 
         root["tmpUnits"] = getSetting("tmpUnits", TMP_UNITS).toInt();
+        root["tmpCorrection"] = getSetting("tmpCorrection", TMP_CORRECTION).toFloat();
 
         #if HOMEASSISTANT_SUPPORT
             root["haVisible"] = 1;

code/html/custom.js

@@ -811,7 +811,9 @@ function processData(data) {
         if (key == "tmpUnits") {
             $("span#tmpUnit").html(data[key] == 1 ? "ºF" : "ºC");
         }
-
+        if (key == "tmpCorrection") {
+            $("span#tmpCorrection").val(data[key]);
+        }
         // Look for INPUTs
         var element = $("input[name=" + key + "]");
         if (element.length > 0) {

code/html/index.html

@@ -436,6 +436,15 @@
                                     <div class="pure-u-1 pure-u-sm-1-4"><input type="radio" name="tmpUnits" tabindex="15" value="1"> Fahrenheit (&deg;F)</input></div>
                                 </div>
 
+                                <div class="pure-g module module-ds module-dht">
+                                    <label class="pure-u-1 pure-u-md-1-4" for="tmpCorrection">Temperature correction</label>
+                                    <input name="tmpCorrection" class="pure-u-1 pure-u-md-3-4" type="number" action="reset" min="-100" step="0.1" max="100" tabindex="6" />
+                                    <div class="pure-u-0 pure-u-md-1-4">&nbsp;</div>
+                                    <div class="pure-u-1 pure-u-md-3-4 hint">
+                                      Temperature correction value is added to the measured value which may be inaccurate due to many factors. The value can be negative.
+                                    </div>
+                                </div>
+
                             </fieldset>
                         </div>
                     </div>