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@ -38,6 +38,23 @@
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* \section Module Description
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* Device Mode USB Class driver framework interface, for the CDC USB Class driver.
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*
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* \note There are several major drawbacks to the CDC-ACM standard USB class, however
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* it is very standardized and thus usually available as a built-in driver on
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* most platforms, and so is a better choice than a proprietary serial class.
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*
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* One major issue with CDC-ACM is that it requires two Interface descriptors,
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* which will upset most hosts when part of a multi-function "Composite" USB
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* device, as each interface will be loaded into a separate driver instance. To
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* conbat this, you should use the "Interface Association Descriptor" addendum to
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* the USB standard which is available on most OSes when creating Composite devices.
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*
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* Another major oversight is that there is no mechanism for the host to notify the
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* device that there is a data sink on the host side ready to accept data. This
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* means that the device may try to send data while the host isn't listening, causing
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* lengthy blocking timeouts in the transmission routines. To combat this, it is
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* recommended that the virtual serial line DTR (Data Terminal Ready) be used where
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* possible to determine if a host application is ready for data.
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*
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* @{
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*/
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Dean Camera
15 years ago