Hi, I have tried several times the Android and Arduino Hello World Tutorial in different ways , using both ADKToolkit 0.2.0 and the latest ADKToolkit 0.3.0 from https://github.com/palazzem/adk-toolkit. See my previous post http://www.udoo.org/forum/threads/a...rld-tutorial-null-point-exception-error.3744/ The Arduino sketch works perfect but I am having trouble running the Android program. While running the app , the layout appears but once the button is clicked the app crashes (I have tried toggle button, switch, image View and button) . The log shows Null pointer Exception caused by this particular line all the time adkManager.write("1"); // the function write is used in ADKToolkit 0.3.0 instead of writeSerial from the previous version. How can you avoid this error?? Is there something missing in the adkManger class of the ADKtoolkit ? or the write function( derived from OutputStream class) be replaced by some other function??