Update Pi README.md

Author: sarweshkumar47

picode/digital-twin-device/README.md

@@ -1,4 +1,4 @@
-# How to run openplc-ditto demo on Raspberry Pi
+# How to run digital-twin demo on Raspberry Pi
 
 * Go to picode/digital-twin-device directory
 
@@ -26,12 +26,26 @@
   python ditto_demo.py
   ```
 
+# Data logging  
+* Log file will be automatically created in the following path:
+
+        picode/digital-twin-device/logs/
+
+* To extract the log file at any time, simply run a basic http server in RaspberryPi.
+
+        $ cd picode/digital-twin-device/logs/
+        $ python -m SimpleHTTPServer 9001
+        
+* Open a browser from any local machine and type the IP address and port number in the following format:
+
+        http://10.114.56.110:9001
+  
 # Run WebUI
 
 To monitor the sensor values and interact with the Raspberry Pi, view the WebUI in your Browser. 
 Simply open /webapp/index.html.
 
 You should see the following view:
 <p align="center" >
-  <img src="https://github.com/sarweshkumar47/Digital-Twin/blob/master/images/openplc-ditto-demo-webapp-sample.png" alt="demo" width="100%"/> 
+  <img src="https://github.com/sarweshkumar47/Digital-Twin/blob/master/images/digital-twin-demo-webapp-sample.png" alt="demo" width="100%"/> 
 </p>