sgp40 docs doxygen

Author: mikeysklar

src/components/i2c/drivers/WipperSnapper_I2C_Driver_SGP40.h

@@ -147,13 +147,25 @@ class WipperSnapper_I2C_Driver_SGP40 : public WipperSnapper_I2C_Driver {
 
 protected:
   Adafruit_SGP40 *_sgp40; ///< SGP40
-  // background accumulation state
+
+  /** Millis timestamp of last 1 Hz background read. */
   uint32_t _lastFastMs = 0;
+
+  /** Number of samples accumulated since last publish. */
   uint32_t _n = 0;
+
+  /** Running sum of VOC index samples for averaging. */
   float _vocSum = 0.0f;
+
+  /** Running sum of raw samples for averaging. */
   uint32_t _rawSum = 0;
 
-  // enable fast sampling if either output is requested
+  /*******************************************************************************/
+  /*!
+      @brief  Returns whether VOC background sampling should be active.
+      @return True if either VOC Index or raw value is configured to publish.
+  */
+  /*******************************************************************************/
   inline bool vocEnabled() {
     return (getSensorVOCIndexPeriod() > 0) || (getSensorRawPeriod() > 0);
   }