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<concept id="GUID-529757E6-ABF2-5C5C-A995-7DED6D298F52" xml:lang="en"><title>Design</title><shortdesc>This topic describes how to design the USB client controller

for different types of USB hardware.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>On most hardware platforms, the variant is split into a common,

or ASSP, layer and a device specific, or variant, layer; for example,

the Symbian port for the template board is split into a core layer

for the ASSP (in <filepath>...\template_assp\...</filepath>) and code

specific to the template board (in <filepath>...\template_variant\...</filepath>). </p>

<p>On some hardware configurations, the USB platform-specific layer

functionality is not only dependent on the USB device controller (in

the ASSP) but also on the variant. As an example, the USB cable connection/disconnection

notification mechanism is not defined in the USB specification. This

means that some USB device controllers have a mechanism for detecting

the status of a cable connection that is internal to the ASSP, while

for other controllers the mechanism is variant specific, and requires

software support in the variant layer. </p>

<p>In the template example port, the ASSP layer is implemented by

the <codeph>TemplateAssp</codeph> class defined in <filepath>...\template_assp\template_assp_priv.h</filepath>. This class defines a number of pure virtual functions that act

as the interface to the cable connection status mechanism. </p>

<codeblock id="GUID-4E7ED63E-5383-53D8-AC79-29AE307B1FED" xml:space="preserve">class TemplateAssp : public Asic

    {

    ...

  /**

     * USB client controller - Some example functions for the case that USB cable detection and

     * UDC connect/disconnect functionality are part of the variant.

     * Pure virtual functions called by the USB PSL, to be implemented by the variant (derived class).

     * If this functionality is part of the ASSP then these functions can be removed and calls to them

     * in the PSL (./pa_usbc.cpp) replaced by the appropriate internal operations.

     */

    virtual TBool UsbClientConnectorDetectable()=0;

    virtual TBool UsbClientConnectorInserted()=0;

    virtual TInt RegisterUsbClientConnectorCallback(TInt (*aCallback)(TAny*), TAny* aPtr)=0;

    virtual void UnregisterUsbClientConnectorCallback()=0;

    virtual TBool UsbSoftwareConnectable()=0;

    virtual TInt UsbConnect()=0;

    virtual TInt UsbDisconnect()=0;

</codeblock>

<p>In the template example port, the variant layer is implemented

by the <codeph>Template</codeph> class defined in <filepath>...\template_variant\inc\variant.h</filepath>. The variant layer provides the implementation for these USB pure

virtual functions. </p>

<codeblock id="GUID-D697E009-5C21-5C7A-A31A-7A526413655E" xml:space="preserve">NONSHARABLE_CLASS(Template) : public TemplateAssp

    {

    ...

     /**

     * USB client controller - Some example functions for the case that USB cable detection and

     * UDC connect/disconnect functionality are part of the variant.

     * These virtual functions are called by the USB PSL (pa_usbc.cpp).

     * If this functionality is part of the ASSP then these functions can be removed as calls to them

     * in the PSL will have been replaced by the appropriate internal operations.

     */

    virtual TBool UsbClientConnectorDetectable();

    virtual TBool UsbClientConnectorInserted();

    virtual TInt RegisterUsbClientConnectorCallback(TInt (*aCallback)(TAny*), TAny* aPtr);

    virtual void UnregisterUsbClientConnectorCallback();

    virtual TBool UsbSoftwareConnectable();

    virtual TInt UsbConnect();

    virtual TInt UsbDisconnect();

</codeblock>

<p>The implementation for these functions can be found in <filepath>...\template_variant\specific\variant.cpp</filepath>. </p>

<p>The USB port also needs interrupt handling code to deal with USB

external interrupts. See the <xref href="GUID-3C34724F-B476-5329-B0B1-6D5A34294979.dita">Interrupt Dispatcher

Tutorial</xref> for details about how to do this. </p>

<note>This may be done by others as a specialist porting activity. </note>

</conbody></concept>