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ISO-transfer and USB HUB #41
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Furthermore, i also see 2 request being generated using pyusb, so it might being an driver issue?
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Hi
I developing both the device and host end for an embedded system, where the host will serve as a control "panel" for the device.
I am using C# binding for libusbK, where i am having some issues, which i now believe i have point pointed to somewhere in my host application.
The issue:
I am using iso-transfers between the host and device to "steam" process data. This works fine without a hub attached, but once the host and device communicates through any usb HUB i get issues. Based on my USB analysis tool (Beagle 480), it seems that the following code generates 2 iso-transfer requests:
I came to that conclusion by placing a breakpoint right after this line, but the USB-sniffer report that the request was made twice. see the screenshot below. Because 2 requests are quickly after each other, the device if unable to re-arm the endpoint in time, and the resulting in a data payload of 0-bytes for the following transfer request. How, this does not always happens.
The issues get worse with large data payload, and do not occur for every transfer. I am really puzzled by this, and it might not be related to libusbK, but i was hoping someone might have an idea. Does anyone know if there exists some tool/software where i could quickly test this issue?
The screenshot below shows that this "double" event does not always occur. Ideally, I am trying to send a request every 10 frames, which can also be seen on the timestamp. However, when i have the double event the second event is always right after the first..
The device: microchip DSPIC33.
If this is outside the scope of this library, i am sorry.
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