@ -51,6 +51,9 @@ USB_ClassInfo_Audio_Device_t Microphone_Audio_Interface =
} ,
} ;
/** Current audio sampling frequency of the streaming audio endpoint. */
uint32_t CurrentAudioSampleFrequency = 48000 ;
/** Main program entry point. This routine contains the overall program flow, including initial
* setup of all components and the main program loop .
@ -133,7 +136,7 @@ void EVENT_USB_Device_Connect(void)
/* Sample reload timer initialization */
TIMSK0 = ( 1 < < OCIE0A ) ;
OCR0A = ( ( F_CPU / 8 / AUDIO_SAMPLE_FREQUENCY ) - 1 ) ;
OCR0A = ( ( F_CPU / 8 / CurrentAudioSampleFrequency ) - 1 ) ;
TCCR0A = ( 1 < < WGM01 ) ; // CTC mode
TCCR0B = ( 1 < < CS01 ) ; // Fcpu/8 speed
}
@ -163,3 +166,72 @@ void EVENT_USB_Device_ControlRequest(void)
Audio_Device_ProcessControlRequest ( & Microphone_Audio_Interface ) ;
}
/** Audio class driver callback for the setting and retrieval of streaming endpoint properties. This callback must be implemented
* in the user application to handle property manipulations on streaming audio endpoints .
*
* When the DataLength parameter is NULL , this callback should only indicate whether the specified operation is valid for
* the given endpoint index , and should return as fast as possible . When non - NULL , this value may be altered for GET operations
* to indicate the size of the retreived data .
*
* \ note The length of the retrieved data stored into the Data buffer on GET operations should not exceed the initial value
* of the \ c DataLength parameter .
*
* \ param [ in , out ] AudioInterfaceInfo Pointer to a structure containing an Audio Class configuration and state .
* \ param [ in ] EndpointProperty Property of the endpoint to get or set , a value from Audio_ClassRequests_t .
* \ param [ in ] EndpointIndex Index of the streaming endpoint whose property is being referenced .
* \ param [ in ] EndpointControl Parameter of the endpoint to get or set , a value from Audio_EndpointControls_t .
* \ param [ in , out ] DataLength For SET operations , the length of the parameter data to set . For GET operations , the maximum
* length of the retrieved data . When NULL , the function should return whether the given property
* and parameter is valid for the requested endpoint without reading or modifying the Data buffer .
* \ param [ in , out ] Data Pointer to a location where the parameter data is stored for SET operations , or where
* the retrieved data is to be stored for GET operations .
*
* \ return Boolean true if the property get / set was successful , false otherwise
*/
bool CALLBACK_Audio_GetSetEndpointProperty ( USB_ClassInfo_Audio_Device_t * const AudioInterfaceInfo ,
const uint8_t EndpointProperty ,
const uint8_t EndpointIndex ,
const uint8_t EndpointControl ,
uint16_t * const DataLength ,
uint8_t * Data )
{
/* Check the requested endpoint to see if a supported endpoint is being manipulated */
if ( EndpointIndex = = Microphone_Audio_Interface . Config . DataINEndpointNumber )
{
/* Check the requested control to see if a supported control is being manipulated */
if ( EndpointControl = = AUDIO_EPCONTROL_SamplingFreq )
{
/* Check the requested property to see if a supported property is being manipulated */
if ( EndpointProperty = = AUDIO_REQ_SetCurrent )
{
/* Check if we are just testing for a valid property, or actually adjusting it */
if ( DataLength ! = NULL )
{
/* Set the new sampling frequency to the value given by the host */
CurrentAudioSampleFrequency = ( ( ( uint32_t ) Data [ 2 ] < < 16 ) | ( ( uint32_t ) Data [ 1 ] < < 8 ) | ( uint32_t ) Data [ 0 ] ) ;
/* Adjust sample reload timer to the new frequency */
OCR0A = ( ( F_CPU / 8 / CurrentAudioSampleFrequency ) - 1 ) ;
}
return true ;
}
else if ( EndpointProperty = = AUDIO_REQ_GetCurrent )
{
/* Check if we are just testing for a valid property, or actually reading it */
if ( DataLength ! = NULL )
{
* DataLength = 3 ;
Data [ 2 ] = ( CurrentAudioSampleFrequency > > 16 ) ;
Data [ 1 ] = ( CurrentAudioSampleFrequency > > 8 ) ;
Data [ 0 ] = ( CurrentAudioSampleFrequency & 0xFF ) ;
}
return true ;
}
}
}
return false ;
}
Dean Camera
14 years ago