# SNDEX_IsConnectedHeadphoneAsync

## Syntax

  `#include <twl/snd.h>`

      SNDEXResult SNDEX_IsConnectedHeadphoneAsync( SNDEXHeadphone *hp, SNDEXCallback callback, void* arg );

## Arguments

hp | Pointer to a `SNDEXHeadphone` variable, which stores the result of the check to determine whether headphones are connected. A value is written to this variable asynchronously, so it must not be used for anything else until asynchronous processing is complete.
callback | `SNDEXCallback`-type function that is notified when the asynchronous process has completed. The asynchronous process runs even if `NULL` is specified here, but you are no longer able to detect that it has completed.
arg | Argument to pass to the function specified in callback.

## Return Values

### Function Return Values

`SNDEX_RESULT_SUCCESS` | Asynchronous processing started successfully. The asynchronous processing results are passed as an argument to the function registered in callback.
`SNDEX_RESULT_ILLEGAL_STATE` | This function has been called on the NITRO platform.
`SNDEX_RESULT_BEFORE_INIT` | Extended sound features have not been initialized by the `SNDEX_Init` function.
`SNDEX_RESULT_EXCLUSIVE` | Processing for other extended sound features is running. Note that mutexes are used for each of the extended sound features, so they cannot be used simultaneously. As mentioned in the SNDEX Library Overview, the error also returns during processing of shutter sound playback.
`SNDEX_RESULT_PXI_SEND_ERROR` | A PXI command failed to be sent to the ARM7. This error occurs when the PXI send queue for the ARM7 has filled up or when the hardware has detected an error. As a result, the state may improve when a retry is made.

### Asynchronous Process Results

`SNDEX_RESULT_SUCCESS` | The whole series of operations completed successfully.
`SNDEX_RESULT_EXCLUSIVE` | A mutex error occurred in the ARM7. This error depends upon the progress of ARM7 processing, so conditions may improve when a retry is made.
`SNDEX_RESULT_DEVICE_ERROR` | This notification is sent when the ARM7's internal operation failed to get the speaker volume for an external device. Conditions may improve on a retry, but continued failures after multiple retries could indicate that the external device is not responding, so you may handle this as if it were a notification of success. A value of 0 is stored in volume when this error occurs.
`SNDEX_RESULT_FATAL_ERROR` | This error should not ordinarily occur. This may occur when an illegal PXI command was sent directly, ignoring library state management; when the ARM7 component and the extended sound feature library have different versions; when library state management has fallen into an abnormal state due to memory corruption; or when other such conditions arise. There is no way to recover from this at run time.

## Description

Asynchronously gets a value indicating whether headphones are connected.

If this function does not return a value of `SNDEX_RESULT_SUCCESS`, the asynchronous processing and callback do not run. Also note that a PXI receive interrupt sends notification when the asynchronous processing is complete, so callbacks do not occur if PXI receive interrupts are prohibited.

## See Also

`SNDEX_IsConnectedHeadphone`

## Revision History

2008/11/07 Added mention that `SNDEX_RESULT_EXCLUSIVE` is returned during processing of shutter sound playback.
2008/11/06 Corrected Asynchronous Process Results (`SNDEX_RESULT_EXCLUSIVE`) in Return Values.
2008/10/27 Revised explanation in Arguments.
2008/10/27 Initial version.

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