added setHeaterLevel function

src/HTU21D.cpp

@@ -186,6 +186,33 @@ void HTU21D::setHeater(HTU21D_HEATER_SWITCH heaterSwitch)
  write8(HTU21D_USER_REGISTER_WRITE, userRegisterData);
 }
 
+/**************************************************************************/
+/*
+ setHeaterLevel()
+
+ Set the Heater level (between 3.09 mA and 94.20 mA, see datasheet)
+
+ NOTE:
+ - prolonged exposure to high humidity will result gradual upward drift
+ of the RH reading, the heater is used to drive off condensation &
+ reverse drift effect.
+ - heater consumtion is 3.09mA - 94.20mA @ 3.3v.
+*/
+/**************************************************************************/
+void HTU21D::setHeaterLevel(byte heaterLevel)
+{
+ uint8_t heaterRegisterData = 0;
+
+ heaterRegisterData = read8(HTU21D_HEATER_REGISTER_READ);
+
+ heaterLevel &= 0x0F;
+ heaterRegisterData &= 0xF0;
+ heaterRegisterData |= heaterLevel;
+
+ write8(HTU21D_HEATER_REGISTER_WRITE, heaterRegisterData);
+}
+
+
 /**************************************************************************/
 /*
  readHumidity()

src/HTU21D.h

@@ -133,6 +133,7 @@ class HTU21D
  void softReset(void);
  bool batteryStatus(void);
  void setHeater(HTU21D_HEATER_SWITCH heaterSwitch);
+ void setHeaterLevel(byte heaterLevel);
  uint16_t readDeviceID(void);
  uint8_t readFirmwareVersion(void);