Welcome to JavaDoesUSB discussions!

[manuelbl]

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[q2q-2q2]

for Fedora libudev installed via

dnf install libgudev libgudev-devel

[manuelbl]

I can reproduce the error with the USB to serial device. It occurs because a system driver is loaded for the device. The system driver can be unloaded and in a prototype implementation it already works.

More investigation is needed to come up with a suitable interface (should the driver be unloaded automatically or only with a separate operation, should the driver be reattached automatically etc.)

[manuelbl]

And regarding the Fedora packages: From what I can see, the minimal package to install would be systemd-libs.

[manuelbl]

The main branch now contains code to automatically unload the kernel driver. So your code for the CH340G should now be able to claim the interface. This works on Linux only. On Windows, the driver must be replaced with the WinUSB driver first. And on macos, I don't understand yet how the driver can be unloaded.

The main branch also contains a fix so that libgudev-devel is no longer needed on Linux. A default Linux installation should likely work.

[gospodbucar]

How to set little or big endian?

I also encountered a problem with interacting with device. It successfuly open and print - but i get an error trying to send or read endpoint (Exception in thread "main" net.codecrete.usb.windows.WindowsUsbException: transfer IN on endpoint 1 failed: An invalid parameter was passed to a service or function. (error code: -1073741811))

I was previously using java4usb library and i wanted to upgrade.

have any ideas?

[manuelbl]

Hi @gospodbucar

What would you need a little ending / big ending setting for? Can you describe the use case?

The error you are getting could be a bug. I'd like to fix it but will need more information. Can you open a new issue with it. I would need:

• The code that leads to the error. If possible, a small but complete program. Otherwise sufficient code to reproduce it.
• If possible, the output of the enumeration example program (the part related to the USB device that you want to communicate with is sufficient)

Am I correct assuming that you are using Java 21 and the latest version of this library?

[mattias-berglund]

Hi!

Thanks for the good job you've done creating this library, it suits my needs perfectly! However, I ran into a snag today when trying out my application on a Raspberry Pi:

Nov 13 12:46:01 raspberrypi launch.sh[2481]: Exception in thread "USB async IO" java.lang.IndexOutOfBoundsException: Index 1 out of bounds for length 1
Nov 13 12:46:01 raspberrypi launch.sh[2481]:         at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)
Nov 13 12:46:01 raspberrypi launch.sh[2481]:         at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:124)
Nov 13 12:46:01 raspberrypi launch.sh[2481]:         at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:448)
Nov 13 12:46:01 raspberrypi launch.sh[2481]:         at java.base/java.util.Objects.checkIndex(Objects.java:441)
Nov 13 12:46:01 raspberrypi launch.sh[2481]:         at java.base/jdk.internal.foreign.LayoutPath.addScaledOffset(LayoutPath.java:243)
Nov 13 12:46:01 raspberrypi launch.sh[2481]:         at net.codecrete.usb.linux.LinuxAsyncTask.asyncCompletionTask(LinuxAsyncTask.java:101)
Nov 13 12:46:01 raspberrypi launch.sh[2481]:         at java.base/java.lang.Thread.run(Thread.java:1575)

It occurs if a try to handle two devices simultaneously, e.g. if two devices are available when the program starts. I'm running 1.1.0 on java23 (OpenJDK 64-Bit Server VM (build 23.0.1+11-snap, mixed mode, sharing)). Is there something I'm missing regarding thread safety in JavaDoesUSB or is it a bug?

[manuelbl]

Thanks for reporting it. I will look into it. The library is generally multi-threading safe. It looks like a bug.

[manuelbl]

I was able to reproduce the bug and fix it in version 1.1.1. It will soon be available on Maven Central.

[mattias-berglund]

Thanks for your swift response - now works like a charm!