Hello, I've just joined this list and have trouble with my USB device.
I have EZ-USB (AN2131SC and AN2135SC) development boards and trying to
make them
work as Communication Class Devices with Abstract Control Model so that
I can use
Apple's CDC USB driver and can access them via /dev/cu.usbmodemXXXX.
There is a downloadable firmware to make EZ-USB a Communication Class
Device
with Abstract Control Model.
It works fine if I connect my board directly to my iMac USB port.
(I made a JTAG downloader out of the firmware.)
But it does not work with USB hubs.
Currently, I do not have any debugging tools for the target boards.
(I have AVR STK500 starter kit and am trying to make a debugger for
EZ-USB)
But some experiments show that, while the write() system call succeeds,
the first read() system call to the device does not return and it
generates the message:
75.331 [1] AppleUSBOHCI[0x1d03000]::CreateGeneralTransfer - trying
to queue to a stalled pipe
I suspect that some device request is sent to my device prior to bulk
read request and
cause the firmware to stall.
Can anyone give me hints? I am also grateful to any advice about
debugging.
Thanks in advance.
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