Add more usage details to the Readme

README.org

@@ -12,3 +12,17 @@
   arduino-cli sketch new Test
   ./compile.sh Test
 #+END_SRC
+
+   If you want to see the output of the Serial port, you have to identify the device:
+
+#+BEGIN_SRC sh
+  arduino-cli board list
+#+END_SRC
+    
+   Then you can see the output of the device, let's assume that the device is /dev/ttyACM0:
+   
+#+BEGIN_SRC sh
+  cat /dev/ttyACM0
+#+END_SRC
+
+   If you get a /Permission denied/, try running the command as a superuser (e.g. *sudo*)