Support LM75 temperature sensor (#1327)

* First draft of LM75 sensor based on HTU21 sensor

* Initialise I2C on ESP8266

* Add LM75 sensor to test builds

So that it will be tested with the continuous integration

main/ZsensorLM75.ino

@@ -0,0 +1,99 @@
+/*
+  OpenMQTTGateway Addon  - ESP8266 or Arduino program for home automation
+
+   Act as a wifi or ethernet gateway between your 433mhz/infrared IR signal  and a MQTT broker
+   Send and receiving command by MQTT
+
+   This is a Temperature Addon:
+   - Measures Temperature
+   - Generates Values for: Temperature in degrees C and F
+   - Required Hardware Module: LM75 or NCT75
+   - Required Library: jeremycole/I2C Temperature Sensors derived from the LM75
+
+   Connection Schemata:
+   --------------------
+
+   LM75 ------> Arduino Uno ----------> ESP8266
+   ==============================================
+   Vcc ---------> 5V -------------------> Vu (5V)
+   GND ---------> GND ------------------> GND
+   SCL ---------> Pin A5 ---------------> D1
+   SDA ---------> Pin A4 ---------------> D2
+
+    This file is part of OpenMQTTGateway.
+
+    OpenMQTTGateway is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenMQTTGateway is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "User_config.h"
+
+#ifdef ZsensorLM75
+#  include <stdint.h>
+
+#  include "Temperature_LM75_Derived.h"
+#  include "Wire.h" // Library for communication with I2C / TWI devices
+#  include "config_LM75.h"
+
+//Time used to wait for an interval before resending measured values
+unsigned long timelm75 = 0;
+
+//Global sensor object
+Generic_LM75 lm75Sensor;
+
+void setupZsensorLM75() {
+  delay(10); // Gives the Sensor enough time to turn on
+  Log.notice(F("LM75 Initialized - begin()" CR));
+
+#  if defined(ESP32)
+  Wire.begin(I2C_SDA, I2C_SCL);
+#  elif defined(ESP8266)
+  Wire.begin();
+#  endif
+}
+
+void MeasureTemp() {
+  if (millis() > (timelm75 + TimeBetweenReadinglm75)) {
+    Log.trace(F("Read LM75 Sensor" CR));
+
+    timelm75 = millis();
+    static float persisted_lm75_tempc;
+
+    float lm75TempC = lm75Sensor.readTemperatureC();
+
+    if (lm75TempC >= 998) {
+      Log.error(F("Failed to read from sensor LM75!" CR));
+      return;
+    }
+
+    // Check if reads failed and exit early (to try again).
+    if (isnan(lm75TempC)) {
+      Log.error(F("Failed to read from sensor HLM75!" CR));
+    } else {
+      Log.notice(F("Creating LM75 buffer" CR));
+      StaticJsonDocument<JSON_MSG_BUFFER> jsonBuffer;
+      JsonObject LM75data = jsonBuffer.to<JsonObject>();
+      // Generate Temperature in degrees C
+      if (lm75TempC != persisted_lm75_tempc || lm75_always) {
+        float lm75TempF = (lm75TempC * 1.8) + 32;
+        LM75data["tempc"] = (float)lm75TempC;
+        LM75data["tempf"] = (float)lm75TempF;
+        pub(LM75TOPIC, LM75data);
+      } else {
+        Log.notice(F("Same Temp. Don't send it" CR));
+      }
+    }
+    persisted_lm75_tempc = lm75TempC;
+  }
+}
+
+#endif