Got those baud rate blues

Pyrotom

Why did I decide to work with the Javelin Stamp? Because I'm a Java guy, that's why! So I was understandably a little disappointed when all of the sample code for communicating with the Javelin through the JavelinIDE port was in C++ (and Pascal??). When I complained a little about this, Peter Verkaik posted a rough cut at a Java version of his terminal program (thanks, Peter!).

So I started from that - it looked easy enough - all I had to do was add the code to use the javax.comm package to open a serial port at 28.8K, 8 bits, 1 stop bit, no parity. I'd used the javax.comm package before and didn't expect any problems. Wrong! Attempting to open the serial port throws an UnsupportedCommOperationException with the message "Unsupported baud rate".

The serial port can clearly do 28800 baud rate, since the JavelinIDE does it, so I started poking around. Disassembling the Win32SerialPort class in javax.comm, I found that the check the requested baud rate against a table with 75, 110, 134, 150, 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200. Uh, oh.

So I go to the Sun website to see if there is maybe an update. Much to my surprise, I find that there is indeed a new 3.0 version of javax.comm, but not for Windows. As a matter of fact, there is now NO version of javax.comm available for windows!

So at the moment, I'm SOL. The Javelin chip does not support the MIDI baud rate of 31.25K needed for one of my projects, and the only baud rate it supports for the JavaIDE port is not supported by javax.comm, thus stopping my other project. Sigh. Just got them old baud rate blues...

Peter Verkaik

Here is something for you to read:

http://students.spsu.edu/gear/files/gear_javelin_experience.doc

regards peter

Peter Verkaik

Here is a serial demo that adds 28800 baud.

regards peter

Pyrotom

Yeah, I know I could use the other serial port, but I'm a little short of I/O pins, so the JIDE port looked attractive. Besides, I was hoping to convert the entire JIDEport support code to Java, as a first step towrds building an Eclipse plugin for Javelin programming....

Peter Verkaik

The serialdemo adds 28800 baud, so you could use the jide port.

Once you have the·baudrate you can filter out the metadata easily.

regards peter

Pyrotom

Hmmm. What version of javax.comm are you using? My version (2.0) does not have a class SerialConnection...

Peter Verkaik

I have no idea. It is code I found by googling for

javax 28800 baud

http://www.mit.edu/afs/net/dev/user/foley/share/java/commapi/samples/SerialDemo/SerialDemo.java

There were more results. Try it.

regards peter

Pyrotom

Can't try it, as it won't compile. That code is from 1998, and was probably using javax.comm 1.0. Sigh.

Peter Verkaik

I think this is it.

regards peter

Pyrotom

A friend clued me in to the DJ Java Decompiler <http://members.fortunecity.com/neshkov/dj.html>. I used it to decompile the Win32SerialPort class in javax.comm, add 28800 to the list of supported baud rates, and then recompiled it and put it in my class path ahead of javax.comm. This worked just fine, and I'm talking to the Javelin. Score at this point: Javelin 1, Sun 0. They were limiting their supported baud rates for absolutely no reason.

Peter Verkaik

Great! Now you need to implement the protocol. One way of doing that is in

the attached code. Just replace the Javelin send and receive by your

API send and receive. To send bytes you must fill up the array cmdbuf

and when the array is filled with a command, make cmd true.

The receive state machine will send the bytes from cmdbuf to the javelin

once the javelin requests data. Once cmdbuf is emptied, cmd is set false.

regards peter