Update README.md

README.md

@@ -12,7 +12,7 @@ The sensor abstraction layer is also useful for data-logging and data-transmissi
 
 ## How Does it Work? ##
 
-There are two main typedefs and one enum defined in Adafruit_Sensor.h that must be used by any sensor driver that you want to be compliant with the abstraction layer:
+Any driver the supports the Adafruit Sensor Abstraction Layer will implement the Adafruit\_Sensor base class.  There are two main typedefs and one enum defined in Adafruit_Sensor.h that are used to 'abstract' away the sensor details and values:
 
 **Sensor Types (sensors\_type\_t)**
 
@@ -111,6 +111,20 @@ It includes the following fields:
 - **timestamp**: time in milliseconds when the sensor value was read
 - **data[4]**: An array of four 32-bit values that allows us to encapsulate any type of sensor data via a simple union (further described below)
 
+**Required Functions**
+
+In addition to the two standard types and the sensor type enum, all drivers based on Adafruit_Sensor must also implement the following two functions:
+
+```
+void getEvent(sensors\_event\_t*);
+```
+Calling this function will populated the supplied sensors\_event\_t reference with the latest available sensor data.  You should call this function as often as you want to update your data.
+
+```
+void getSensor(sensor_t*);
+```
+Calling this function will provide some basic information about the sensor (the sensor name, driver version, min and max values, etc.
+
 **Standardised SI values for sensors\_event\_t**
 
 A key part of the abstraction layer is the standardisation of values on SI units of a particular scale, which is accomplished via the data[4] union in sensors\_event\_t above.  This 16 byte union includes fields for each main sensor type, and uses the following SI units and scales:
@@ -174,4 +188,4 @@ Serial.print  ("Min Value:    "); Serial.print(sensor.min\_value); Serial.printl
 Serial.print  ("Resolution:   "); Serial.print(sensor.resolution); Serial.println(" lux");  
 Serial.println("------------------------------------");
 Serial.println("");
-```
+```