Update of README file with documentation and example

README.md

@@ -1,2 +1,63 @@
 # microSDI12
-A mini SDI-12 implementation for getting sensor info through UART
+A mini SDI-12 implementation for getting sensor info over UART. Supports simple RS-232 and directional RS-485.
+
+# API
+
+## class SDI12
+**\__init__** (pin_txd, pin_rxd, pin_direction, uart_bus_id)
+  * TX pin name
+  * RX pin name
+  * Direction pin name (optional)
+  * UART bus id (optional, default = 1)
+
+**is_active** (address)
+  * args:
+    * SDI-12 sensor address. Typical range: 0-9.
+  * returns:
+    * Boolean: whether the sensor has send back acknowledgement
+
+**get_sensor_info** (address)
+  * args:
+    * SDI-12 sensor address. Typical range: 0-9.
+  * returns:
+    * Tuple (manufacturer, model): The manufacturer and model name as reported by the sensor. If sensor is unreachable, returns `(None, None)`
+
+**get_measurement** (address)
+
+Sends a request for data measurement to the sensor and returns the data provided by the sensor.
+  * args:
+    * SDI-12 sensor address. Typical range: 0-9.
+  * returns:
+    * Measurement data: a string line containing a typical measurement. For data format and parsing, please advise sensor manufacturer manuals. If sensor is unreachable, returns `None`
+
+
+# Example
+
+```python
+from microsdi12 import SDI12
+
+sdi12 = None
+
+try:
+    sdi12 = SDI12("P3", "P4", "P8", 1)
+
+    manufacturer = None
+    model = None
+    sensor_response = None
+    address = "1"
+
+    if sdi12.is_active(address):
+        manufacturer, model = sdi12.get_sensor_info(address)
+        sensor_response = sdi12.get_measurement(address)
+        response_array = sdi12.measurement_to_array(sensor_response)
+except Exception as e:
+    print("Exception while reading SDI-12 data")
+finally:
+    if sdi12:
+        sdi12.close()
+```
+
+
+# links
+ * https://docs.micropython.org/en/latest/library/machine.UART.html
+ * https://docs.pycom.io/firmwareapi/pycom/machine/uart/