feat(ess): Update with bsec info

Documentation/bluetooth/ess.rst

@@ -15,12 +15,22 @@ It provides:
 - Relative humidity
 - Pressure
 
+If :ref:`bsec_api` is enabled the following additional estimates are available:
+
+ - Indoor air quality (IAQ estimate
+ - Equivalent CO2 (eCO2) estimate
+
+Please refer to :ref:`bme680` for more information about BSEC.
+
 
 If notifcations are enabled a measurement of all values is performed every 3 seconds. For each measurement a notification is sent for the characteristics which have notifications enabled.
 
 
 A measurement can also be triggered by reading from a characteristic. A measurement takes roughly 200 ms. A notifciation will be sent to all characteristics which have notifications enabled except the one which was used to trigger the measurement.
 
+.. note::
+   If :ref:`bsec_api` is enabled, reading a characteristic will not trigger a new measurement.
+
 
 BLE Service
 -----------
@@ -44,6 +54,11 @@ BLE Service
   UUID: ``2A6D``
   read and notify
 
+- Indoor air quality (IAQ) characteristic:
+
+  UUID: ``422302f1-2342-2342-2342-234223422342``
+  read and notify
+
 Temperature characteristic
 ---------------------------------
 
@@ -65,3 +80,20 @@ Pressure characteristic
 - 32 bit little endian value representing the measured pressure.
 
 - Unit: 0.1 Pa (0.001 hPa)
+
+Indoor air quality (IAQ) characteristic
+---------------------------------
+
+Data format:
+
+======== =========================== ===========================
+Byte 0   Bytes 1-2                   Bytes 3-4
+-------- --------------------------- ---------------------------
+Accuracy IAQ (16-bit little endian)  eCO2 (16-bit little endian)
+======== =========================== ===========================
+
+
+Units:
+
+- Accuracy and IAQ units: See :ref:`bsec_api` API description
+- CO2 unit: [ppm]