2.3.4.5 USB_DEVICE_AUDIO_StatusSend Function

C

USB_DEVICE_AUDIO_RESULT USB_DEVICE_AUDIO_StatusSend(
    USB_DEVICE_AUDIO_INDEX instanceIndex, 
    USB_DEVICE_AUDIO_TRANSFER_HANDLE* transferHandle, 
    USB_AUDIO_INTERRUPT_STATUS_WORD* status
);

Summary

This function requests a status write to the USB Device Audio Function Driver Layer. The function places a requests with driver to arm the status interrupt Endpoint with the status provided, the request will get serviced as data is requested by the USB Host. A handle to the request is returned in the transferHandle parameter. The termination of the request is indicated by the USB_DEVICE_AUDIO_EVENT_STATUS_SEND_COMPLETE event.

The transfer handle expires when event handler for the USB_DEVICE_AUDIO_EVENT_STATUS_SEND_COMPLETE exits. If the Status Send request could not be accepted, the function returns an error code and transferHandle will contain the value USB_DEVICE_AUDIO_TRANSFER_HANDLE_INVALID.

Description

Description of the function.

Precondition

The USB Device should be in a configured state. The USB Configuration descriptor must contain Status interrupt Endpoint descriptor.

Parameters

Returns

• USB_DEVICE_AUDIO_RESULT_OK - The Status send request was successful. transferHandle contains a valid transfer handle.
• USB_DEVICE_AUDIO_RESULT_ERROR_TRANSFER_QUEUE_FULL - internal request queue is full. The status send request could not be added.
• USB_DEVICE_AUDIO_RESULT_ERROR_INSTANCE_NOT_CONFIGURED - The specified instance is not configured yet.
• USB_DEVICE_AUDIO_RESULT_ERROR_INSTANCE_INVALID - The specified instance was not provisioned in the application and is invalid.

Example

 // Shows an example of how to Submit Status Send request to Host. This assumes 
 // that device has been configured. 

 USB_DEVICE_AUDIO_INDEX instanceIndex;
 USB_DEVICE_AUDIO_TRANSFER_HANDLE transferHandle;
 // Following must have __attribute__((coherent, aligned(16))) for PIC32MZ 
 USB_AUDIO_INTERRUPT_STATUS_WORD statusWord; 
 USB_DEVICE_AUDIO_RESULT statusSendResult; 

 //specify the Audio Function driver instance number.
 instanceIndex = 0; 

 // Fill in Status Word 
 statusWord.bOriginator = 0x01; //ID of the terminal  
 statusWord.originator =  0x00; //Audio Control interface 
 statusWord.memoryContentsChanged = 1; //Memory contents changed 
 statusWord.interruptPending = 1; //Interrupt is pending 

 statusSendResult = USB_DEVICE_AUDIO_StatusSend ( instanceIndex, &transferHandle,
                         &statusWord);

 if(USB_DEVICE_AUDIO_RESULT_OK != statusSendResult)
 {
     //Do Error handling here
 }

 // The completion of the read request will be indicated by the
 // USB_DEVICE_AUDIO_EVENT_STATUS_SEND event. The transfer handle
 // will be returned along with the event.

Remarks

While the using the Audio Function Driver with PIC32MZ USB module, the audio buffer provided to the USB_DEVICE_AUDIO_StatusSend function should be placed in coherent memory and aligned at a 16 byte boundary. This can be done by declaring the buffer using the __attribute__((coherent, aligned(16))) attribute. An example is shown here

USB_AUDIO_INTERRUPT_STATUS_WORD statusWord __attribute__((coherent, aligned(16)));