Using Java to talk to an embedded system

A longtime customer has asked me to build a PC-hosted GUI to control
an existing system I designed for him a long time ago. Actually the
system was designed to control a vending machine, but he now wants to
use the same hardware as a sort of poor man's PLC, to operate various
other machinery in his facility.

I don't like wasting effort on Windows-specific code if I don't have
to, so I was thinking of writing the GUI in Java.

Can anyone who has been down this path (i.e. talking to an embedded
system over serial from a PC running a JVM) give any tips on the pros
and cons of using something like javacomm vs. JNI? (I figure the JNI
DLL would be <100 lines of code, just wrapping a few comm functions).

Thanks.

larwe wrote:
> A longtime customer has asked me to build a PC-hosted GUI to control
> an existing system I designed for him a long time ago. Actually the
> system was designed to control a vending machine, but he now wants to
> use the same hardware as a sort of poor man's PLC, to operate various
> other machinery in his facility.
> 
> I don't like wasting effort on Windows-specific code if I don't have
> to, so I was thinking of writing the GUI in Java.
> 
> Can anyone who has been down this path (i.e. talking to an embedded
> system over serial from a PC running a JVM) give any tips on the pros
> and cons of using something like javacomm vs. JNI? (I figure the JNI
> DLL would be <100 lines of code, just wrapping a few comm functions).
> 

Hi Lewin,

This no doubt is not particularly helpful but I use a java telnet applet
to talk to an embedded system which is online here:

http://www.cybertheque.org/homebrew/rcvr

The embedded controller talks over RS-232 to a terminal server which
is accessed by the telnet applet.

Embedded in the web page, the opportunity for GUI window dressing presents
itself; I also use VT-100 graphics in the telnet session for GUI-like
features (not particularly evident in my example yet).

Regards,

Michael

On Fri, 15 Jun 2007 07:48:54 -0700, larwe wrote:

> I don't like wasting effort on Windows-specific code if I don't have
> to, so I was thinking of writing the GUI in Java.
> 
> Can anyone who has been down this path (i.e. talking to an embedded
> system over serial from a PC running a JVM) give any tips on the pros
> and cons of using something like javacomm vs. JNI? (I figure the JNI
> DLL would be <100 lines of code, just wrapping a few comm functions).

If it was for Linux that you wanted I would have happily emailed you some
JNI code, but alas, for Windows, I don't have any. But you are right, the
JNI code is basically wrapper code.

You may also want to have a look at groovy - it has something called
SwingBuilder to easily build Swing apps (easier than using Java). You can
find some examples on the Groovy in Action book's website. In future, I
can see myself using Groovy/Javacomm for simple GUI apps with serial port.

You might have seen from sun's website that the latest Javacomm from sun
now supports Linux/Solaris but not Windows. Previous versions supported
Solaris/Windows but not Linux. I think you can get a windows compatible
version off the net somewhere (not written by sun).

HTH

Paul.

On Jun 15, 1:12 pm, Paul Taylor <paul_ng_pls_...@tiscali.co.uk> wrote:


> > and cons of using something like javacomm vs. JNI? (I figure the JNI
> > DLL would be <100 lines of code, just wrapping a few comm functions).
>
> If it was for Linux that you wanted I would have happily emailed you some
> JNI code, but alas, for Windows, I don't have any. But you are right, the

Oh, I can write the JNI stuff. That's no problem. Actually, I will do
the development in MacOS anyway :) My question is, asking someone
who's already tried to do something of this sort, whether it is a
better prospect to look for native Java solutions or just go the
simple route with JNI.

On Fri, 15 Jun 2007 17:27:29 +0000, larwe wrote:

> whether it is a
> better prospect to look for native Java solutions or just go the
> simple route with JNI.

Well I have always gone the JNI route, and found it to work as expected.
But as in my previous post, next time I will try javacomm + groovy,
because it means I can write the sorts of simple apps I write using a
scripting language + existing library, then drop the c compiler +
makefile. I _suspect_ javacomm also works as expected. I will look with
interest to see if anyone posts to your original question anything that
puts me off ;-)

Regards,

Paul.

On Jun 15, 1:49 pm, Paul Taylor <paul_ng_pls_...@tiscali.co.uk> wrote:


> But as in my previous post, next time I will try javacomm + groovy,
> because it means I can write the sorts of simple apps I write using a

Well, I was pointed to this:
<http://en.wikibooks.org/wiki/Serial_Programming:Serial_Java>
which is extremely interesting. I'll experiment with that this
weekend.

Yay Intarwebs.

I had a lot of luck with using a JNI interface to a USB DLL. With
something as straight forward as serial communications, it should be a
snap.