Advice for debugging a communication issue when using pyusb

Hi @jonasmalacofilho and @mcuee,

I’m using pyusb in my spectrometer library python-seabreeze and a user reported an issue where communication with a specific spectrometer model via pyusb works on Windows, but fails on Linux. Another different type of spectrometer works on both of the user’s operating systems, so we can rule out some library installation issue.

We have debug logs that were created with LIBUSB_DEBUG=4 and PYUSB_DEBUG=debug from the Linux and the Windows machine. On both machines the pyusb backend is libusb1 and the libusb library version is v1.0.24.11584

❌   Here is the linux log: https://github.com/ap--/python-seabreeze/issues/133#issuecomment-926065589 ✅   And here the windows log: https://github.com/ap--/python-seabreeze/issues/133#issuecomment-926073213

The linux log shows that a timeout occurs when it’s trying to read information back after the first command. But I’m out of ideas what the issue could be.

Could you give me some advice how to best proceed with the debugging here?

Thank you so much, Cheers, Andreas 😃

[ap--]

Thank you so much for your help @mcuee I’ll go and ask the linux-usb mailing list then. In the meantime I will close this issue, and report back with whatever I find out.

Thanks again, Andreas 😃

[mcuee]

Unfortunately the capture does not tell much. The first bulk-in failed under Linux. I will suggest you ask in linux-usb mailing list to get better help. I can only think that the many control requests in the beginning somewhat put the device into a wrong state under Linux.

linux-usb mailing list. http://vger.kernel.org/vger-lists.html#linux-usb

Frame 115: 27 bytes on wire (216 bits), 27 bytes captured (216 bits)
USB URB
    [Source: host]
    [Destination: 1.3.1]
    USBPcap pseudoheader length: 27
    IRP ID: 0xffffb08a631744e0
    IRP USBD_STATUS: Unknown (0xffffffff)
    URB Function: URB_FUNCTION_BULK_OR_INTERRUPT_TRANSFER (0x0009)
    IRP information: 0x00, Direction: FDO -> PDO
        0000 000. = Reserved: 0x00
        .... ...0 = Direction: FDO -> PDO (0x0)
    URB bus id: 1
    Device address: 3
    Endpoint: 0x81, Direction: IN
        1... .... = Direction: IN (1)
        .... 0001 = Endpoint number: 1
    URB transfer type: URB_BULK (0x03)
    Packet Data Length: 0
    [bInterfaceClass: Vendor Specific (0xff)]