Cannot read data from the /dev/ttyUSB0 with the Java sample for the Magician dobot


#1

Using the Java sample of the DobotDemoV2.0 package for the Magician it crashes always
see my call and the results below:

after debugging with qDebug calls I found the reason, the app couldn’t read any data back from the /dev/ttyUSB0 port where the dobot was connected. Why is the program not able to read any data back, can anybody tell me the reason.

I use ubuntu v18.04 LTS with qt 5.9.5 and Java 1.8.0_45 I also recompiled the DobotDll with release and the debug version it was always the same result

the java call was

$ java -cp lib/jna-4.2.2.jar:bin/:bin/CPlusDll/:jnalib/lib/debug/ Main

the output:

$ sudo chmod 666 /dev/ttyUSB0
$ sudo chown otmar:dialout /dev/ttyUSB0
$ java -cp lib/jna-4.2.2.jar:bin/:bin/CPlusDll/:jnalib/lib/debug/ Main
CDobotConnector : QThread(0x7f3c3c2685c0)
CDobotProtocol : QThread(0x7f3c3c2687b0)
CDobotCommunicator : QThread(0x7f3c3c269960)

A fatal error has been detected by the Java Runtime Environment:

SIGSEGV (0xb) at pc=0x00007f3c1d8b2dd1, pid=25201, tid=139896031696640

JRE version: Java™ SE Runtime Environment (8.0_45-b14) (build 1.8.0_45-b14)

Java VM: Java HotSpot™ 64-Bit Server VM (25.45-b02 mixed mode linux-amd64 compressed oops)

Problematic frame:

C [libDobotDll_d.so+0x40dd1] CDobotConnector::connectDobot(void*, void*, void*, unsigned int, void*, void*)+0x539

Failed to write core dump. Core dumps have been disabled. To enable core dumping, try “ulimit -c unlimited” before starting Java again

An error report file with more information is saved as:

/home/otmar/eclipse-workspace/Dobotest1/hs_err_pid25201.log

If you would like to submit a bug report, please visit:

http://bugreport.java.com/bugreport/crash.jsp

Abgebrochen (Speicherabzug geschrieben)


#2

Hi Otmar,
could you figure out what the problem was? Same issue here! Tested with MAC and Windows Environment, same situation. Any help is greatly appreciated!


#3

PS. the DLLs seem fine as they work via the Python Demos, must/should relate to the Java environment, am I right?