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  1. #1
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    Jun 2008
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    USB Connection problems

    Hello,

    I've connected a N95 to an embedded target via the USB 2.0 interface. The embedded target is the USB HOST. In the process of "enumerating" the N95, the host is requesting the various configuration descriptors. To make a long story short, it does not appear that the N95 is supplying the ENDPOINT_DESCRIPTOR table. What is the reason for omitting this descriptor from the configuration list?

    Thanks
    Last edited by LanceMProctor; 2008-09-03 at 20:39.

  2. #2
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    Re: USB Connection problems

    I think the problem could be due to a limitation on the USB controller that I am using. End-Point 0 can only Rx & Tx 64 bytes at a time. The Configuration Descriptor specifies a total size of 0x1d2:
    0x09 0x02 0xD2 0x01 0x10 0x01 0x04 0xC0 0x32 0x00. As such, I think I am missing a significant portion of the descriptor list. Is this plausable? If so, is it possible to request "portions" of the descriptor list as a workaround? Any suggestions?

    If this is the case

  3. #3
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    Re: USB Connection problems

    Hi Lance,

    Unless the phone is somehow broken, it always returns as much of the configuration descriptor and the following interface and endpoint descriptors as the host requests.

    Get descriptor startdard request does not allow you getting descriptors in parts (i.e. while you can provide the length of the descriptor you can not define offset, so the returned set of descriptor always starts from the beginning of the config descriptor).

    However you should be able to read the content of the host controller buffer then free the buffer and then keep receiving the rest of the descriptor(s). Implementation of this depends on your host controller and its drivers.

    t.Tero

  4. #4
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    Re: USB Connection problems

    Yeah, the problem is confirmed to be with respect to the controller. What I am trying to do is access the phone's serial port interface over the USB. Its kind of confusing, as the interface descriptor defines a Communication Interface (0x02), then a CDC Data descriptor (0x0a) followed by the endpoint definitions. I presume the endpoints associated with this interface number are the interfaces to the serial port interface?
    If not, what interface number defines the N95's serial port ?

  5. #5
    Regular Contributor
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    Re: USB Connection problems

    Hello Lance I just came across your thread and wondered if you solved your problem as I am also trying to set up a micro controller with USB host capability and I simply want to read/write serial data. I have the phone sending characters but have trouble configuring the USB host to read the characters because I am not sure which end points I should be using eg bulk transfer in/out? Any assistance most appreciated!

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