[Rxtx] getPortIdentifiers(); returning null enumertion
tjarvi at qbang.org
Mon Aug 14 18:06:29 MDT 2006
On Mon, 14 Aug 2006, Ed wrote:
> When I try to get the mode with int mode = pPort.getMode(); it returns 0
> which isn't any of the valid modes. I tried setting it explicitely with
> pPort.setMode(ParallelPort.LPT_MODE_XXX );and all failed with
> gnu.io.UnsupportedCommOperationException: setLPRMode was unable to proced
> the requested mode in nativeSetSerialPortParams
> at gnu.io.LPRPort.setLPRMode(Native Method)
> at gnu.io.LPRPort.setMode(LPRPort.java:87)
> Except for LPT_MODE_ANY, but the getMode call still failed out with an
> invalid state.
This is because rxtx only supports the basics.
JNIEXPORT jboolean JNICALL LPRPort(setLPRMode)(JNIEnv *env,
jclass jclazz, jint mode)
throw_java_exception( env, UNSUPPORTED_COMM_OPERATION,
"setLPRMode was unable to proced the requested \
One could program in more support. When I did that I just had a daisy
wheel printer to test with and doing any more would have been blind.
So that behavior is expected. I'll look to see if the Parallel Complete
book mentions which pins you need to raise. If you look in the source
code [ParallelImp.c] you can see this code isn't well tested. It has
worked for hobby use in the past as I'd guess you are trying to do. But
my experience with the code is as is mentioned in the top of the source:
fear he who enter here. It appears that things have changed. An attempt
has been made to put things the way the should be.
It compiles and ParallelBlackBox runs. No further guarantees.
Well... One.. it will print "Hello World!" on an epson DX 10 printer.
you know.. the 10 character per second daisy wheel printer ;)
- Trent Jarvi
That comment is from 1997 or so.
Since then some windows support was contributed but it is still very green
code. We get about four requests for parallel support a year so its just
not a well traveled area.
It would be nice to have some documentation for the people trying to hook
parallel ports to electronic projects. That appears to be the exclusive
use of the Parallel support. The wiki pages are intended to let people
share information like this to help each other in their projects as they
figure out the details.
tjarvi at qbang.org
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