Add documentation to the USB Class Drivers module on how to use the Host mode class drivers.

1 files changed, 109 insertions, 0 deletions

diff --git a/LUFA/Drivers/USB/USB.h b/LUFA/Drivers/USB/USB.h
index d1bf17aa3..a632f52e2 100644
--- a/LUFA/Drivers/USB/USB.h
+++ b/LUFA/Drivers/USB/USB.h
@@ -235,7 +235,116 @@
  *  class-specific functions.

  *

  *  \subsection SSec_ClassDriverHost Host Mode Class Drivers

+ *  Implementing a Host Mode Class Driver in a user application requires a number of steps to be followed. Firstly,

+ *  the module configuration and state structure must be added to the project source. These structures are named in a 

+ *  similar manner between classes, that of <i>USB_ClassInfo_<b>{Class Name}</b>_Host_t</i>, and are used to hold the

+ *  complete state and configuration for each class instance. Multiple class instances is where the power of the class 

+ *  drivers lie; multiple interfaces of the same class simply require more instances of the Class Driver's ClassInfo 

+ *  structure.

+ *

+ *  Inside the ClassInfo structure lies two sections, a <i>Config</i> section, and a <i>State</i> section. The Config

+ *  section contains the instance's configuration parameters, and <b>must have all fields set by the user application</b>

+ *  before the class driver is used. Each Device mode Class driver typically contains a set of configuration parameters

+ *  for the endpoint size/number of the associated logical USB interface, plus any class-specific configuration parameters.

+ *

+ *  The <i>State</i> section of the ClassInfo structures are designed to be controlled by the Class Drivers only for

+ *  maintaining the Class Driver instance's state, and should not normally be set by the user application.

+ *

+ *  The following is an example of a properly initialized instance of the MIDI Class Driver structure:

+ *

+ *  \code

+ *  USB_ClassInfo_MIDI_Host_t My_MIDI_Interface =

+ *  {

+ *      .Config =

+ *          {

+ *              .DataINPipeNumber       = 1,

+ *              .DataINPipeDoubleBank   = false,

+ *              

+ *              .DataOUTPipeNumber      = 2,

+ *              .DataOUTPipeDoubleBank  = false,

+ *          },

+ *  };

+ *  \endcode

+ *

+ *  To initialize the Class driver instance, the driver's <i><b>{Class Name}</b>_Host_ConfigurePipes()</i> function

+ *  should be called in response to the host state machine entering the \ref HOST_STATE_Addressed state. This function

+ *  will return an error code from the class driver's <i><b>{Class Name}</b>_EnumerationFailure_ErrorCodes_t</i> enum

+ *  to indicate if the driver sucessfully initialized the instance and bound it to an interface in the attached device.

+ *  Like all the class driver functions, this function takes in the address of the specific instance you wish to initialize

+ *  - in this manner, multiple seperate instances of the same class type can be initialized. A fragment of a Class Driver

+ *  based Host mode application may look like the following:

+ *

+ *  \code

+ *      switch (USB_HostState)

+ *      {

+ *          case HOST_STATE_Addressed:

+ *              LEDs_SetAllLEDs(LEDMASK_USB_ENUMERATING);

+ *          

+ *              uint16_t ConfigDescriptorSize;

+ *              uint8_t  ConfigDescriptorData[512];

+ *

+ *              if (USB_Host_GetDeviceConfigDescriptor(1, &ConfigDescriptorSize, ConfigDescriptorData,

+ *                                                     sizeof(ConfigDescriptorData)) != HOST_GETCONFIG_Successful)

+ *              {

+ *                  LEDs_SetAllLEDs(LEDMASK_USB_ERROR);

+ *                  USB_HostState = HOST_STATE_WaitForDeviceRemoval;

+ *                  break;

+ *              }

+ *

+ *              if (MIDI_Host_ConfigurePipes(&My_MIDI_Interface,

+ *                                           ConfigDescriptorSize, ConfigDescriptorData) != MIDI_ENUMERROR_NoError)

+ *              {

+ *                  LEDs_SetAllLEDs(LEDMASK_USB_ERROR);

+ *                  USB_HostState = HOST_STATE_WaitForDeviceRemoval;

+ *                  break;

+ *              }

+ *

+ *              // Other state handler code here

+ *  \endcode

+ *

+ *  Note that the function also required the device's configuration descriptor so that it can determine which interface

+ *  in the device to bind to - this can be retrieved as shown in the above fragment using the

+ *  \ref USB_Host_GetDeviceConfigDescriptor() function. If the device does not implement the interface the class driver

+ *  is looking for, if all the matching interfaces are already bound to class driver instances or if an error occurs while

+ *  binding to a device interface (for example, a device endpoint bank larger that the maximum supported bank size is used)

+ *  the configuration will fail.

  *

+ *  Once initialized, it is important to maintain the class driver's state by repeatedly calling the Class Driver's

+ *  <i><b>{Class Name}</b>_Host_USBTask()</i> function in the main program loop. The exact implementation of this

+ *  function varies between class drivers, and can be used for any internal class driver purpose to maintain each

+ *  instance. Again, this function uses the address of the instance to operate on, and thus needs to be called for each

+ *  seperate instance, just like the main USB maintenance routine \ref USB_USBTask():

+ *

+ *  \code

+ *  int main(void)

+ *  {

+ *      SetupHardware();

+ *  

+ *      LEDs_SetAllLEDs(LEDMASK_USB_NOTREADY);

+ *  

+ *      for (;;)

+ *      {

+ *          switch (USB_HostState)

+ *          {

+ *             // Host state machine handling here

+ *          } 

+ *      

+ *          MIDI_Host_USBTask(&My_Audio_Interface);

+ *          USB_USBTask();

+ *      }

+ *  }

+ *  \endcode

+ *

+ *  Each class driver may also define a set of callback functions (which are prefixed by "CALLBACK_"

+ *  in the function's name) which <b>must</b> also be added to the user application - refer to each

+ *  individual class driver's documentation for mandatory callbacks. In addition, each class driver may

+ *  also define a set of events (identifiable by their prefix of "EVENT_" in the function's name), which

+ *  the user application <b>may</b> choose to implement, or ignore if not needed.

+ *

+ *  The individual Host Mode Class Driver documentation contains more information on the non-standardized,

+ *  class-specific functions which the user application can then use on the driver instances, such as data

+ *  read and write routines. See each driver's individual documentation for more information on the

+ *  class-specific functions.

  */

  

 #ifndef __USB_H__