Question

Ultimately I would like to use a Java program to send and receive messages from a phone that I have plugged in via USB. I can do this using a C# program, however the program I want to send and receive messages is written in Java. To do this I am using the Rxtx library (but using the Windows x64 compiled version from Cloudhopper). But whenever I try and send any commands to the phone via USB my computer completely locks up and I have to hard-restart it.

The code I am running is here: Two way communication with the serial port. I think that it successfully establishes a link since it gets to the stage where it accepts input from the console, though when I press enter, and the input is sent, the computer locks up.

I am running Windows 7 x64, using Eclipse. Thank you for any help.

Answer 1

A little hard to tell from the code, but here are some debugging tips:

• Try stepping through the code with the debugger line by line, and step in to the library itself to see if you can find the problem.
• Instead of reading/writing from the console, try sending character codes programmatically. The console operates very differently from direct access. i.e. instead of System.in.read()) just try passing in a known good String.
• Keep in mind that Java works with UCS-16 internally, but that consoles typically work with different character encodings (e.g. cp1252 for Windows). So, your “enter” may be a completely different character from what the system is expecting. If your device is expecting ASCII 13 and your keyboard is generating ASCII 12, that could be enough to confuse things.
• The crash makes it seem very likely that there is something going on with the native library. If you find that the Java debugging keeps dropping you into the JNI boundary, you may need to debug with a C/C++ toolset.

Good luck!