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I have a FX2LP design with a set of descriptors to create a USB audio device. The device implements a speaker, so I have a USB streaming input and a speaker output. The device is recognised by Windows as a USB audio device. However when I open media player and play an mp3 I dont get any data coming out of the FX2LP. I should mention that the FX2 is connected to an FPGA. I have a program monitoring the data coming into the FPGA, but nothing happens. Does anyone have any thoughts? I have attached the file if anyone can see any problems.
Thanks
Jon
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Attachment missing..
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Sorry about the attachement. I have some more info. If I use some software to look at the USB traffic in Windows, I can see that media player tries to send an isochronous transfer. I get the following error. Does anyone know what would cause this error. I can only believe that the descriptor must have a problem.
URB Isoch Transfer failed
Device Object 87C1B3B8h
Driver Object hhdusbh32
URB Function URB_FUNCTION_ISOCH_TRANSFER
URB Status USBD_STATUS_INVALID_PARAMETER
Endpoint 02h 2 Out, Isochronous
Number of Packets 10
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It still hasnt attached the file. I keep adding it but it doesnt appear in the thread.
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Problem solved. As I am using high speed USB the value of bInterval has to be set to 4 to give 1ms.
2 ^ 4-1 = 8
8 x 125us = 1 ms
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