This isn't entirely pyusb related, but it could possibly affect the future of pyusb.
I've been working on an LCD controller, with the goal of being able to control multiple, concurrent devices. I needed USB support for my newest LCD, so I began work on that using pyusb-0.1. However, it became clear pretty quickly that I needed an asynchronous solution, so I set out to work on this wielding ctypes and a fresh copy of libusb-1.0. I've run into some snags, overcoming most (Python's GIL was getting in the way for instance), but there's this one issue that just won't go away. See, the operations work fine synchronously following the steps below in sequence. We can view asynchronous I/O as a 5 step process: 1. Allocation: allocate a libusb_transfer (This is self.transfer) 2. Filling: populate the libusb_transfer instance with information about the transfer you wish to perform (libusb_fill_bulk_transfer) 3. Submission: ask libusb to submit the transfer (libusb_submit_transfer) 4. Completion handling: examine transfer results in the libusb_transfer structure (libusb_handle_events and libusb_handle_events_timeout) 5. Deallocation: clean up resources (Not shown below) However, when performing these steps asynchronously only a portion of the LCD is filled with pixels. I've been through libusb's debug messages and usbmon's output, and between async and sync there are no differences, except when I look at the LCD for the results. I'm starting to believe that this is just not possible with Python+ctypes, which is why I said this could possibly affect pyusb. I am of course hoping for an answer to this, and having some experience in both Python and libusb I'm hoping maybe you would have one. I've attached some code if you feel up to looking into this. Also, I have a question opened at Stackoverflow here: http://stackoverflow.com/questions/1060305/usb-sync-vs-async-vs-semi-async-partially-answered-now
USB4.py
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